how to operate heat pump most efficiently

[uniwelder]

What is the most efficient way to operate a heat pump?  At Green Building Advisor, the advice there seems to be simply to keep the house at one constant temperature to prevent dramatic swings in compressor load.  For background, I have installed two units (2 ton LG wall mount mini split and 3 ton LG air handler, neither with backup resistance heat) myself.  Here are some of my thoughts I hope people could educate me about----

1) COP.  Getting it to work most when outside temps are highest.  If winter averages 40 degrees during the afternoon, but drops to 20 overnight, it makes sense to have it running when its warmest.  Build up heat inside the home during the day and allow it to release at night.

2) Smart thermostats.  The ones I'm familiar with are best suited to instant on gas heat that can get the house up to temp quickly and don't have pricing incentive for midday versus nighttime use like a heat pump would.  There must be thermostats well suited to heat pumps though.  Ones that operate at a rate that will prevent backup resistance heat from coming on and can determine how much time in advance to start warming the house so the unit stays in its most efficient range.  I'm sure they exist, but I just don't know about them.

3) I suppose this is also affected whether your heat pump is single stage, dual stage, or variable/inverter type. Plus whether backup heat is electric resistance or gas, and at what outside temperature the heat pump can no longer keep up or dramatically lowers COP.

Assuming a household that gets up in the morning, goes to work/school, and comes home after 3:00, I would think the most efficient way to utilize a thermostat (smart or not) might have it kick on around noon, get the house warmed by 3:00 pm and maintain that temperature until 10:00 pm, then decrease set point temp by 5 degrees and stay there until noon the next day. 

Can anyone explain their heat pump strategies and cost effectiveness?  Or a good source of information?

edited to add--- flat rate or variable electric rates would also play a big factor.  Efficiency improvements running the unit more during afternoons might be negated by higher electric rates.  In my case, the utility company is on a flat rate system.

[chemistk]

Very much PTF.

We have a 2004 3ton Carrier single stage heat pump, SEER rating unknown, that's on its last legs. It also has (I think) 8kW backup heat.

Our electric bill was absolutely abhorrent for January ($550) - I can attribute over $300 of that to HVAC inefficiency alone. We keep the house at 65 during the day and 61 overnight, and our system struggles to operate in heat pump mode under those conditions. We have a co-branded thermostat, but I have no idea if it's optimized for running the heat pump. It'll run in heat pump mode for about 20 minutes before switching over to resistive heat, sometimes I do know that it's because the coils outside have iced over but other times I feel like the thermostat is impatient. I can measure the air temp coming out of the registers at ~10F above the set temp, but it doesn't seem to like that small delta.

We have a quote for a pretty vanilla system, mostly because supply chain issues mean that getting anything over the entry level system is dicey at best. I asked for a new quote on a more efficient system but I haven't heard back from them on it.

We've already gone around and snuffed out the most obvious air sealing issues in the house, but for the remainder of the season I too am curious about the most efficient heat pump operating conditions.

[afox]

No matter your source of heat I think that it is most efficient to use the heat like a lightswitch, turn off/as low as possible when not home and on when home. Of course assuming it doesnt take hours to heat up the space which would make using the heat like a light switch impractical.

This is why I have avoided heating systems with high latency (time between changing temp on thermostat and actual air temperature change) such as in floor radiant heating. Although some of these systems with high latency may be "efficient" (defined as high percentage of energy consumed going into heating the space) they would cost more to run for me since I am okay with turning heat off when not home and waiting a few min for house to warm up when I get home. I have always had adequately sized forced air gas furnaces which take 10 minutes or so to raise the temperature 10f so can turn the heat down to the low fifties when leaving home and back to 69 or so when home. Temp doesnt get down to low fifties unless gone for a really long time so typically only takes 10 min or less to go from 60f or so to a comfortable temp after being gone for the day...

I suppose if the heatpump is incapable of operating in heat pump mode in the temperatures you live in then it obviously is'nt practical. Sounds like heat pump tech has evolved such that units operate in heat pump mode in negative Fahrenheit temperatures now. I would also want a heat pump to be sized appropriately to have the ability to warm the home about 1f per minute. Sounds like you need new equipment.

[uniwelder]

No matter your source of heat I think that it is most efficient to use the heat like a lightswitch, turn off/as low as possible when not home and on when home. Of course assuming it doesnt take hours to heat up the space which would make using the heat like a light switch impractical....

...I suppose if the heatpump is incapable of operating in heat pump mode in the temperatures you live in then it obviously is'nt practical. Sounds like heat pump tech has evolved such that units operate in heat pump mode in negative Fahrenheit temperatures now. I would also want a heat pump to be sized appropriately to have the ability to warm the home about 1f per minute. Sounds like you need new equipment.

It sounds like you aren't familiar with heat pumps, and probably would take a lot of adjusting to get used to their operation.  Just because they don't work the way you'd like them to doesn't mean they aren't effective or efficient.  Also, your natural gas unit that gets your house toasty warm in 10 minutes is likely oversized 3x, which seems pretty common. 

In my case, the units I installed operate at full capacity below my coldest temps with no electric resistance heat.  I haven't had an issue with them failing to keep the house warm and am quite happy.  Chemistk does seem to have issues, but is looking to get that resolved.  The question at hand is how to run a heat pump most efficiently.

edited to add--- As an example of how grossly oversized systems can be, my old house was a 750 sq ft, 2 bedroom home built in 1950.  The oil furnace, probably from the 80's, was over 5 tons.  I'm calculating that based on the 'small' .6 gph nozzle and assumed efficiency of 80%.  It never ran more than 1/4 of the time even in the coldest temps.  I replaced it with a 1.5 ton mini split when we renovated the house, and even that was probably bigger than needed.  That mini-split did an excellent job, but I'm always looking for ways to improve.

[KarefulKactus15]

Set backs are most efficient, but only if you have a thermostat that isn't stupid about it.

Most thermostats will panic and fire heat strips when the temp is 2 degrees below desired temp. Also some control boards have an additional setting not by the thermostat that if heat is requested for x minutes (usually 20) then it will fire heat strips until the heat call is removed.

You need a thermostat with thermal modeling for maximum efficiency.  Nest does this, I think ecobee and other do also.

Once you step into that tier of thermostat, where they are wifi and take the outside weather and previous data collection into account for making future decisions.....  Well then you can be efficient.

Until then your thermostat is going to waste those savings from setting back 6 degrees all night when it runs the heat strips full blast at 6am in a panic attempt to reheat the home. 

So if you have a dumb thermostat, you won't gain much if you set back past the emergency heat threshold.

I can't comment on gas backup heat as I'm not currently aware of the exchange price delta between has and electric btu.    Heat pump is ez since it's about 3x more efficient that resistance heat down to 40s outdoor.


Also final note - if you suspect your system wasn't setup for efficiency, it wasn't.   Most systems are setup by the install ler for COMFORT at all cost.   Comfort is what creates call backs. Nobody calls the HVAC guy cause their system is wasting power, they call when the system isn't making them comfortable.

[LD_TAndK]

I have a heat pump in Maryland, I use a Nest thermostat which has a setting called "Max savings" that only uses electric coil heat when absolutely necessary. The heat pump can still manage to pump heat in the single digits, albeit slowly. This January I estimate we averaged 15 kWh used for heat on a daily basis.

The nest can estimate how far in advance to start heating, but I don't use that feature. I have it start heating at 6 AM and hold that temp till 6 PM.

If I'm expecting a big temperature swing one day, say It's 15 degrees, and I know it'll be 40 at noon, I'll delay heating the house for a couple hours in the morning.

I also have a couple space heaters that my wife and I use on the coldest days as local heat, so we don't have to crank the whole house.

[MMMarbleheader]

It took me a while to come around but for my mini split the best is to do nothing. Set the fan speed to auto and the temp to 67 all the time. I messed with setbacks, fans speeds, etc. and the most efficient I have found was just to leave it alone and let it do it's thing.

I have a ranch the mini split blows down the hall so putting a fan in the far room on low blowing cold air to the unit really helps move the warm air to the end of the house

[bacchi]

We also have a mini-split but we adjust it: cooler at night, warmer during the day. This works financially and for comfort year round.

As for the heat pump water heater, I try to time my showers for the warmest point of the day. I've never seen the backup coils turn on with normal use but I have turned it off when the workshop eased into the 20s overnight (this is rare because it's attached, insulated, and south facing).

[Just Joe]

We have two split gas furnaces. Currently burning propane. I recently had a gas line run at $1500 (b/c acreage) b/c math says gas is cheaper and the propane company prices are just high.

We rent the tank so we can't change suppliers to chase best prices. I almost bought a new tank so I could but nat gas math won.

As the furnaces wear out we'll switch to heat pump hybrids. My family has defaulted to heat pumps since the 1970s and supplemented with a wood fireplace when there were winter storms and power outages.

DW and I bought a hybrid system at our last house with a thermostat adjustable switch over setpoint. We chose a set point around freezing.

As our current units wear out, we plan to return to that kind of setup.

I've tested the ideas mentioned here and what has worked for us the best has been to set the thermostat to 65F and leave it. Last night was near freezing and we wanted a bit more heat so we used the gas logs for 2-3 hours to warm up the family room.

When the gas logs are used I've noticed the thermostats rarely come on so we might just be moving heat costs from the furnace to the gas logs.

Something I've wondered about - thermal mass. If the house is allowed to cool too much, then isn't there an energy cost from heating up the structure of the house and its contents too?

I will likely invest in smart thermostats at some point. Our house gets full sun so in the winter we do benefit from a sunny day even with dumb digital thermostats.

The big efficiency challenge is cooling the house. The upstairs unit may not last next summer so we don't cool past ~78F upstairs and ~76F downstairs. Anyone that wants to be cooler needs to grab a tall glass of ice water and sit on the shady porch. 

[lutorm]

From a total heat (or cool) energy point of view it's always better to minimize the delta-T to the outside, that's just how physics works. Having to heat up the house again will always use less energy than having kept it hot. Taking the heat pump efficiency into effect makes it more complicated to calculate the minimum input energy scenario since then, as people pointed out, it might be beneficial to raise the daytime temperature if you're imposing a minimum inside temperature. That's a really interesting question I've not considered before. But then, if electricity rates are higher during the day, too, it might not minimize cost. Makes me want to do some math... ;-)

In the end, it fundamentally depends on what you're optimizing for, though: cost, comfort, or CO2?

[Jon Bon]

Unpopular take here.

I don't like heat pump's
They are expensive to run
I think they are inferior to most other heat sources

So I recently put a heat pump in my attic. After discovering that my installer did it wrong (heat strips not hooked up) we got it working "correctly" Let me tell you, if I was not sleeping during 95% of my experience with it I would be figuring out how to run ducts from my furnace to my second floor.

1. Its cold, sorry blowing air that is 75 degrees is not a pleasant experience. I think I am going to have the blower turned down which is against my techs advice but seriously it pushes out way to much air.
2. Its expensive - my electric bill usage doubled year over year.(feb 21v feb 22) Which might be ok normally, but I have a gas furnace providing heat to 75% of my house (this HP section is new and super insulated)  Not to mention its only providing heat to 400 sqft! Like how is that possible!

So please tell me I am wrong and that I can do something better because this thing is terrible and I am pissed I spent 10k to have it installed.

To be clear I live where we get snow (zone 5 I believe) So if your HP is awesome but you live in Florida I am sure we are not having the same experiences.

[lutorm]

Unpopular take here.

I don't like heat pump's
They are expensive to run
I think they are inferior to most other heat sources

So I recently put a heat pump in my attic. After discovering that my installer did it wrong (heat strips not hooked up) we got it working "correctly" Let me tell you, if I was not sleeping during 95% of my experience with it I would be figuring out how to run ducts from my furnace to my second floor.

1. Its cold, sorry blowing air that is 75 degrees is not a pleasant experience. I think I am going to have the blower turned down which is against my techs advice but seriously it pushes out way to much air.
2. Its expensive - my electric bill usage doubled year over year.(feb 21v feb 22) Which might be ok normally, but I have a gas furnace providing heat to 75% of my house (this HP section is new and super insulated)  Not to mention its only providing heat to 400 sqft! Like how is that possible!

So please tell me I am wrong and that I can do something better because this thing is terrible and I am pissed I spent 10k to have it installed.

To be clear I live where we get snow (zone 5 I believe) So if your HP is awesome but you live in Florida I am sure we are not having the same experiences.

Burning something to make heat is stupid simple... and often cheap, since you're externalizing the cost of emissions.

That said, my family in Sweden use heat pumps successfully, but if it's really cold out they don't give you much beyond pure electric heat.  Where is your evaporator located? If it's in the attic, how is the air in the attic exchanged with the outside? If you put the evaporator in an enclosed space, it'll just cool down that space and then you're not getting any more heat -- you need free outside air flow over it.

[Jon Bon]

Unpopular take here.

I don't like heat pump's
They are expensive to run
I think they are inferior to most other heat sources

So I recently put a heat pump in my attic. After discovering that my installer did it wrong (heat strips not hooked up) we got it working "correctly" Let me tell you, if I was not sleeping during 95% of my experience with it I would be figuring out how to run ducts from my furnace to my second floor.

1. Its cold, sorry blowing air that is 75 degrees is not a pleasant experience. I think I am going to have the blower turned down which is against my techs advice but seriously it pushes out way to much air.
2. Its expensive - my electric bill usage doubled year over year.(feb 21v feb 22) Which might be ok normally, but I have a gas furnace providing heat to 75% of my house (this HP section is new and super insulated)  Not to mention its only providing heat to 400 sqft! Like how is that possible!

So please tell me I am wrong and that I can do something better because this thing is terrible and I am pissed I spent 10k to have it installed.

To be clear I live where we get snow (zone 5 I believe) So if your HP is awesome but you live in Florida I am sure we are not having the same experiences.

Burning something to make heat is stupid simple... and often cheap, since you're externalizing the cost of emissions.

That said, my family in Sweden use heat pumps successfully, but if it's really cold out they don't give you much beyond pure electric heat.  Where is your evaporator located? If it's in the attic, how is the air in the attic exchanged with the outside? If you put the evaporator in an enclosed space, it'll just cool down that space and then you're not getting any more heat -- you need free outside air flow over it.

Evaporator is right outside next to my AC unit.

For some scale I believe the HP running in February to heat 400 sqft used as much energy as my A/C did in August cooling the entire house. Ill see if I cant get my historic electrical usage.

[uniwelder]

Unpopular take here.

I don't like heat pump's
They are expensive to run
I think they are inferior to most other heat sources

So I recently put a heat pump in my attic. After discovering that my installer did it wrong (heat strips not hooked up) we got it working "correctly" Let me tell you, if I was not sleeping during 95% of my experience with it I would be figuring out how to run ducts from my furnace to my second floor.

1. Its cold, sorry blowing air that is 75 degrees is not a pleasant experience. I think I am going to have the blower turned down which is against my techs advice but seriously it pushes out way to much air.
2. Its expensive - my electric bill usage doubled year over year.(feb 21v feb 22) Which might be ok normally, but I have a gas furnace providing heat to 75% of my house (this HP section is new and super insulated)  Not to mention its only providing heat to 400 sqft! Like how is that possible!

So please tell me I am wrong and that I can do something better because this thing is terrible and I am pissed I spent 10k to have it installed.

To be clear I live where we get snow (zone 5 I believe) So if your HP is awesome but you live in Florida I am sure we are not having the same experiences.

Burning something to make heat is stupid simple... and often cheap, since you're externalizing the cost of emissions.

That said, my family in Sweden use heat pumps successfully, but if it's really cold out they don't give you much beyond pure electric heat.  Where is your evaporator located? If it's in the attic, how is the air in the attic exchanged with the outside? If you put the evaporator in an enclosed space, it'll just cool down that space and then you're not getting any more heat -- you need free outside air flow over it.

Evaporator is right outside next to my AC unit.

For some scale I believe the HP running in February to heat 400 sqft used as much energy as my A/C did in August cooling the entire house. Ill see if I cant get my historic electrical usage.

I think the quality of the heat pump and installation makes all the difference.  I'm much too cheap to be paying 10k for someone to install a system.

At what point were you not getting adequate heat without the resistance heater strips working?  The heat pump I just installed has no heat strips--- it puts out its full rated output down to 5 degrees.  In my climate, that's the lowest expected temperature and only happens a few nights of the year. 

I'd be curious to see your electric bill.  A bill doubling from $30 to $60 is a bit different than $200 to $400.  I have no idea where you are on that scale.

[uniwelder]

You need a thermostat with thermal modeling for maximum efficiency.  Nest does this, I think ecobee and other do also.

Once you step into that tier of thermostat, where they are wifi and take the outside weather and previous data collection into account for making future decisions.....  Well then you can be efficient.

Until then your thermostat is going to waste those savings from setting back 6 degrees all night when it runs the heat strips full blast at 6am in a panic attempt to reheat the home. 

So if you have a dumb thermostat, you won't gain much if you set back past the emergency heat threshold.

What if backup resistance heat is shut off, bypassed, or non-existent?  The old thermostat from the 30 year old unit I took out had a bypass switch for resistant heat.  Or someone could shut off the circuit breaker for resistance heat.  Or with my units, it operates at a cold enough temperature to not need backup. 

In those cases, I wonder if setting the temperature back would be fine for the heat pump.  From what I understand, the answer is no, but I don't know why.  Is it because it makes the coils outside defrost excessively whereas it might not need to if it were operated more moderately?  Or is it actually perfectly fine, and more to the point of this posting, more efficient overall, to make the heat pump operate like this?

[uniwelder]

I have a heat pump in Maryland, I use a Nest thermostat which has a setting called "Max savings" that only uses electric coil heat when absolutely necessary. The heat pump can still manage to pump heat in the single digits, albeit slowly. This January I estimate we averaged 15 kWh used for heat on a daily basis.

Damn, that's low.  We about what we would use in our old house--- 750 sq ft with a single mini-split.  We're about double that now since we've moved to a bigger place.  Climate is about comparable.

[uniwelder]

It took me a while to come around but for my mini split the best is to do nothing. Set the fan speed to auto and the temp to 67 all the time. I messed with setbacks, fans speeds, etc. and the most efficient I have found was just to leave it alone and let it do it's thing.

I have a ranch the mini split blows down the hall so putting a fan in the far room on low blowing cold air to the unit really helps move the warm air to the end of the house

How did you go about finding this out?  One year to the next, one month to another, or tracking daily energy use?

[uniwelder]

Something I've wondered about - thermal mass. If the house is allowed to cool too much, then isn't there an energy cost from heating up the structure of the house and its contents too?

The energy released from cooling down (helping to warm the house) is the same amount needed to heat it back up.  Thermal mass helps to moderate heating/cooling loads on hvac equipment.  Used effectively, equipment can be dramatically sized down so it runs at a more constant rate if you want to keep a constant temperature in the house. 

At the other end of things, if you're like @afox and only want heat in small bursts when you're occupying the space, since you might not be home much, then thermal mass isn't really an asset.  I guess thats what nice about oversized furnaces--- it can heat the air in the home for a 10 minute burst and as an occupant, you don't need the objects inside to get warmed up to feel comfortable.

[Gin1984]

I have a heat pump in Maryland, I use a Nest thermostat which has a setting called "Max savings" that only uses electric coil heat when absolutely necessary. The heat pump can still manage to pump heat in the single digits, albeit slowly. This January I estimate we averaged 15 kWh used for heat on a daily basis.

The nest can estimate how far in advance to start heating, but I don't use that feature. I have it start heating at 6 AM and hold that temp till 6 PM.

If I'm expecting a big temperature swing one day, say It's 15 degrees, and I know it'll be 40 at noon, I'll delay heating the house for a couple hours in the morning.

I also have a couple space heaters that my wife and I use on the coldest days as local heat, so we don't have to crank the whole house.

@LD_TAndK I'm in Baltimore and looking to replace my boiler with heat pump.  Would you mind if I PM you to ask some more questions?

[MMMarbleheader]

It took me a while to come around but for my mini split the best is to do nothing. Set the fan speed to auto and the temp to 67 all the time. I messed with setbacks, fans speeds, etc. and the most efficient I have found was just to leave it alone and let it do it's thing.

I have a ranch the mini split blows down the hall so putting a fan in the far room on low blowing cold air to the unit really helps move the warm air to the end of the house

How did you go about finding this out?  One year to the next, one month to another, or tracking daily energy use?

My energy provider gives hour usage data on their website which I used see how much the usage changed day to day. Obviously temperature dependent but I generally knew how much my baseline electricity usage was so the rest was the mini split.

[uniwelder]

It took me a while to come around but for my mini split the best is to do nothing. Set the fan speed to auto and the temp to 67 all the time. I messed with setbacks, fans speeds, etc. and the most efficient I have found was just to leave it alone and let it do it's thing.

I have a ranch the mini split blows down the hall so putting a fan in the far room on low blowing cold air to the unit really helps move the warm air to the end of the house

How did you go about finding this out?  One year to the next, one month to another, or tracking daily energy use?

My energy provider gives hour usage data on their website which I used see how much the usage changed day to day. Obviously temperature dependent but I generally knew how much my baseline electricity usage was so the rest was the mini split.

Could you explain a bit further?  What was your timing and temperature strategy for setbacks?  Would you turn down the temp at night and increase it in the morning?  I definitely see how that can increase energy use, as 6-7 AM is typically the coldest time of a 24 hour period, so the mini-split would be operating most when its least efficient.

[uniwelder]

I have a heat pump in Maryland, I use a Nest thermostat which has a setting called "Max savings" that only uses electric coil heat when absolutely necessary. The heat pump can still manage to pump heat in the single digits, albeit slowly. This January I estimate we averaged 15 kWh used for heat on a daily basis.

The nest can estimate how far in advance to start heating, but I don't use that feature. I have it start heating at 6 AM and hold that temp till 6 PM.

If I'm expecting a big temperature swing one day, say It's 15 degrees, and I know it'll be 40 at noon, I'll delay heating the house for a couple hours in the morning.

I also have a couple space heaters that my wife and I use on the coldest days as local heat, so we don't have to crank the whole house.

@LD_TAndK I'm in Baltimore and looking to replace my boiler with heat pump.  Would you mind if I PM you to ask some more questions?

I'm not who you're asking, but thought I'd throw this out for consideration---- https://www.greenbuildingadvisor.com/article/air-to-water-heat-pump-retrofit

If you're in Maryland, you might already have ductwork set up for air conditioning in the summer, but if not, there are air to water heat pumps that might be able to replace your boiler without a lot of the work required if you want to switch to an air to air heat pump.

[Jon Bon]

Unpopular take here.

I don't like heat pump's
They are expensive to run
I think they are inferior to most other heat sources

So I recently put a heat pump in my attic. After discovering that my installer did it wrong (heat strips not hooked up) we got it working "correctly" Let me tell you, if I was not sleeping during 95% of my experience with it I would be figuring out how to run ducts from my furnace to my second floor.

1. Its cold, sorry blowing air that is 75 degrees is not a pleasant experience. I think I am going to have the blower turned down which is against my techs advice but seriously it pushes out way to much air.
2. Its expensive - my electric bill usage doubled year over year.(feb 21v feb 22) Which might be ok normally, but I have a gas furnace providing heat to 75% of my house (this HP section is new and super insulated)  Not to mention its only providing heat to 400 sqft! Like how is that possible!

So please tell me I am wrong and that I can do something better because this thing is terrible and I am pissed I spent 10k to have it installed.

To be clear I live where we get snow (zone 5 I believe) So if your HP is awesome but you live in Florida I am sure we are not having the same experiences.

Burning something to make heat is stupid simple... and often cheap, since you're externalizing the cost of emissions.

That said, my family in Sweden use heat pumps successfully, but if it's really cold out they don't give you much beyond pure electric heat.  Where is your evaporator located? If it's in the attic, how is the air in the attic exchanged with the outside? If you put the evaporator in an enclosed space, it'll just cool down that space and then you're not getting any more heat -- you need free outside air flow over it.

Evaporator is right outside next to my AC unit.

For some scale I believe the HP running in February to heat 400 sqft used as much energy as my A/C did in August cooling the entire house. Ill see if I cant get my historic electrical usage.

I think the quality of the heat pump and installation makes all the difference.  I'm much too cheap to be paying 10k for someone to install a system.

At what point were you not getting adequate heat without the resistance heater strips working?  The heat pump I just installed has no heat strips--- it puts out its full rated output down to 5 degrees.  In my climate, that's the lowest expected temperature and only happens a few nights of the year. 

I'd be curious to see your electric bill.  A bill doubling from $30 to $60 is a bit different than $200 to $400.  I have no idea where you are on that scale.

Oh I am cheap. Its kind of a longer story, it was an entire new addition so it was new duct work to the HP as well as new duct work to the furnace. Running ducts to the furthest part of the addition was just not practical so a new heat pump was the plan. So the price reflects a bunch of other work than just a new HP.

KWH in  Feb 2021 (no heat pump)  was 665, KWH Feb 2022 1245.

I just don't understand how something can be this expensive to run.  We keep the heat at 66-68.

[Papa bear]

Unpopular take here.

I don't like heat pump's
They are expensive to run
I think they are inferior to most other heat sources

So I recently put a heat pump in my attic. After discovering that my installer did it wrong (heat strips not hooked up) we got it working "correctly" Let me tell you, if I was not sleeping during 95% of my experience with it I would be figuring out how to run ducts from my furnace to my second floor.

1. Its cold, sorry blowing air that is 75 degrees is not a pleasant experience. I think I am going to have the blower turned down which is against my techs advice but seriously it pushes out way to much air.
2. Its expensive - my electric bill usage doubled year over year.(feb 21v feb 22) Which might be ok normally, but I have a gas furnace providing heat to 75% of my house (this HP section is new and super insulated)  Not to mention its only providing heat to 400 sqft! Like how is that possible!

So please tell me I am wrong and that I can do something better because this thing is terrible and I am pissed I spent 10k to have it installed.

To be clear I live where we get snow (zone 5 I believe) So if your HP is awesome but you live in Florida I am sure we are not having the same experiences.

Burning something to make heat is stupid simple... and often cheap, since you're externalizing the cost of emissions.

That said, my family in Sweden use heat pumps successfully, but if it's really cold out they don't give you much beyond pure electric heat.  Where is your evaporator located? If it's in the attic, how is the air in the attic exchanged with the outside? If you put the evaporator in an enclosed space, it'll just cool down that space and then you're not getting any more heat -- you need free outside air flow over it.

Here’s my take on heat pumps as a former heat pump owner and extremely happy not heat pump owner now.

In this area, we burn very dirty stuff to create heat to boil water to turn a turbine to generate electricity. Then we pay to have that electricity run over huge power lines over many miles to finally be plunked down at my house. Then we use that electricity to try and move heat, but it’s cold, uncomfortable, and doesn’t work well, so we just end up taking that electricity to make resistance heat. Lots and lots of efficiency loss.

Or, I can burn some less dirty stuff right at my home and use all that heat to directly warm up my house. 


Sent from my iPhone using Tapatalk

[lukebuz]

1. Its cold, sorry blowing air that is 75 degrees is not a pleasant experience. I think I am going to have the blower turned down which is against my techs advice but seriously it pushes out way to much air.

Read your installation manual for your air handler.  Turn down the CFM per ton to 300.  Yes, it's less than the 400-450 they recommend, but it'll still work just fine, give you a higher outlet temp, be quieter all at once.

[Gin1984]

I have a heat pump in Maryland, I use a Nest thermostat which has a setting called "Max savings" that only uses electric coil heat when absolutely necessary. The heat pump can still manage to pump heat in the single digits, albeit slowly. This January I estimate we averaged 15 kWh used for heat on a daily basis.

The nest can estimate how far in advance to start heating, but I don't use that feature. I have it start heating at 6 AM and hold that temp till 6 PM.

If I'm expecting a big temperature swing one day, say It's 15 degrees, and I know it'll be 40 at noon, I'll delay heating the house for a couple hours in the morning.

I also have a couple space heaters that my wife and I use on the coldest days as local heat, so we don't have to crank the whole house.

@LD_TAndK I'm in Baltimore and looking to replace my boiler with heat pump.  Would you mind if I PM you to ask some more questions?

I'm not who you're asking, but thought I'd throw this out for consideration---- https://www.greenbuildingadvisor.com/article/air-to-water-heat-pump-retrofit

If you're in Maryland, you might already have ductwork set up for air conditioning in the summer, but if not, there are air to water heat pumps that might be able to replace your boiler without a lot of the work required if you want to switch to an air to air heat pump.

I do not have duct work which is why we are looking at a mini split.

[Dancin'Dog]

1. Its cold, sorry blowing air that is 75 degrees is not a pleasant experience. I think I am going to have the blower turned down which is against my techs advice but seriously it pushes out way to much air.

Read your installation manual for your air handler.  Turn down the CFM per ton to 300.  Yes, it's less than the 400-450 they recommend, but it'll still work just fine, give you a higher outlet temp, be quieter all at once.

I hate the cold air blowing.  How do I adjust the fan speed?

[Jon Bon]

1. Its cold, sorry blowing air that is 75 degrees is not a pleasant experience. I think I am going to have the blower turned down which is against my techs advice but seriously it pushes out way to much air.

Read your installation manual for your air handler.  Turn down the CFM per ton to 300.  Yes, it's less than the 400-450 they recommend, but it'll still work just fine, give you a higher outlet temp, be quieter all at once.

Awesome, ok yeah that will solve 1 major problem. Ill try it and check back.

[Cadman]

The thing about heat pumps is they can run all day attempting to make up lost ground if you have a relatively large temp delta you're trying to overcome. In my experience, running the aux heat coils as an assist for 1 hour beats having the unit struggle continuously for 3-4 hours. On our system, the electricity consumed is a wash (14kw x 1hr vs 4.5kw x 3hr), and you save a lot of wear on the compressor and fan bearings (and pump if geo).

I'm running an Ecobee thermostat which does have a lot of flexibility for heat-pumps (and use a couple additional remote sensors), but like anything now, those settings are buried 3 or 4 menus deep. I've often considered building my own smart thermostat that's a better match for these systems. In the summer when we're cooling, I'd rather operate it by time than by temp; it doesn't take much to pull the humidity out of the air to feel good. In the winter, there are times where running the aux strip makes sense to warm the place quickly (nice sunny day on our PV panels) and avoid pulling heat from the ground, especially in late winter. Nothing easily caters to that, AFAIK.

[Jon Bon]

The thing about heat pumps is they can run all day attempting to make up lost ground if you have a relatively large temp delta you're trying to overcome. In my experience, running the aux heat coils as an assist for 1 hour beats having the unit struggle continuously for 3-4 hours. On our system, the electricity consumed is a wash (14kw x 1hr vs 4.5kw x 3hr), and you save a lot of wear on the compressor and fan bearings (and pump if geo).

I'm running an Ecobee thermostat which does have a lot of flexibility for heat-pumps (and use a couple additional remote sensors), but like anything now, those settings are buried 3 or 4 menus deep. I've often considered building my own smart thermostat that's a better match for these systems. In the summer when we're cooling, I'd rather operate it by time than by temp; it doesn't take much to pull the humidity out of the air to feel good. In the winter, there are times where running the aux strip makes sense to warm the place quickly (nice sunny day on our PV panels) and avoid pulling heat from the ground, especially in late winter. Nothing easily caters to that, AFAIK.

Agreed and that is my understanding of it too. We keep ours at a consistent temperature. However during regular operation the heat strips do come on, which is super expensive. Maybe only like 5 mins per hour but its also horrible expensive resistance heat.

[lukebuz]

1. Its cold, sorry blowing air that is 75 degrees is not a pleasant experience. I think I am going to have the blower turned down which is against my techs advice but seriously it pushes out way to much air.

Read your installation manual for your air handler.  Turn down the CFM per ton to 300.  Yes, it's less than the 400-450 they recommend, but it'll still work just fine, give you a higher outlet temp, be quieter all at once.

Awesome, ok yeah that will solve 1 major problem. Ill try it and check back.

Yup!  Most newer units will have a DIP switch to set in a certain order that will set the fan speed.  Each unit different.  Read instruction manual, and aim for 300 CFM per Ton.  4 Ton outdoor unit = 1200 CFM, etc...

[Cranky]

I had to look up what a mini split is, and now I know why I’m always cold at church.

[uniwelder]

I had to look up what a mini split is, and now I know why I’m always cold at church.

So that means there is a mini-split in the church?  If yes, its not the mini-split's fault.  It could be the temp for the building is kept low, or you're standing by a drafty door, or its not blowing in your general direction.  I love my mini-split--- blows warm air, efficient, no ductwork. Churches are terrible wastes of energy--- huge vaulted ceilings, tons of glass, stay empty more than 90% of the time.  You should be glad they don't spend more of your donation money heating it up for a few hours of occupancy.

edited to add--- Maybe I should retract everything I just typed. I suppose the problem could be poor planning and a mini-split isn't the right unit to use.  If the church isn't kept at regular temps constantly, a furnace that puts out craploads of heat for the length of Sunday service is what makes sense.

[uniwelder]

I have a heat pump in Maryland, I use a Nest thermostat which has a setting called "Max savings" that only uses electric coil heat when absolutely necessary. The heat pump can still manage to pump heat in the single digits, albeit slowly. This January I estimate we averaged 15 kWh used for heat on a daily basis.

The nest can estimate how far in advance to start heating, but I don't use that feature. I have it start heating at 6 AM and hold that temp till 6 PM.

If I'm expecting a big temperature swing one day, say It's 15 degrees, and I know it'll be 40 at noon, I'll delay heating the house for a couple hours in the morning.

I also have a couple space heaters that my wife and I use on the coldest days as local heat, so we don't have to crank the whole house.

@LD_TAndK I'm in Baltimore and looking to replace my boiler with heat pump.  Would you mind if I PM you to ask some more questions?

I'm not who you're asking, but thought I'd throw this out for consideration---- https://www.greenbuildingadvisor.com/article/air-to-water-heat-pump-retrofit

If you're in Maryland, you might already have ductwork set up for air conditioning in the summer, but if not, there are air to water heat pumps that might be able to replace your boiler without a lot of the work required if you want to switch to an air to air heat pump.

I do not have duct work which is why we are looking at a mini split.

Not all mini-splits mount to the wall.  There are others called 'short ducted' units that mount up on the ceiling of a large closet or utility room, and can route ducts from there to adjoining rooms.  They're good if for bedrooms with closets or a bathroom between them, or similar situations.  Or a conventional wall mounted unit might be ideal for your space.

[SquashingDebt]

I had to look up what a mini split is, and now I know why I’m always cold at church.

So that means there is a mini-split in the church?  If yes, its not the mini-split's fault.  It could be the temp for the building is kept low, or you're standing by a drafty door, or its not blowing in your general direction.  I love my mini-split--- blows warm air, efficient, no ductwork. Churches are terrible wastes of energy--- huge vaulted ceilings, tons of glass, stay empty more than 90% of the time.  You should be glad they don't spend more of your donation money heating it up for a few hours of occupancy.

edited to add--- Maybe I should retract everything I just typed. I suppose the problem could be poor planning and a mini-split isn't the right unit to use.  If the church isn't kept at regular temps constantly, a furnace that puts out craploads of heat for the length of Sunday service is what makes sense.

I'm very happy with our new heat pump, but it definitely makes me feel chillier than our former propane heater.  We have a very small apartment so where I sit on the couch is in the direct path of the heat pump.  It blows warmer than room temp air, but only by a bit, which feels quite cold when you're already chilly, have wet hair, etc.

[Dancin'Dog]

I think I've heard that there are heat pump water heaters now.  I wonder how they can heat water to a comfortable temp?  Maybe we should all just buy one of those & connect it to radiators... 

[Cranky]

I had to look up what a mini split is, and now I know why I’m always cold at church.

So that means there is a mini-split in the church?  If yes, its not the mini-split's fault.  It could be the temp for the building is kept low, or you're standing by a drafty door, or its not blowing in your general direction.  I love my mini-split--- blows warm air, efficient, no ductwork. Churches are terrible wastes of energy--- huge vaulted ceilings, tons of glass, stay empty more than 90% of the time.  You should be glad they don't spend more of your donation money heating it up for a few hours of occupancy.

edited to add--- Maybe I should retract everything I just typed. I suppose the problem could be poor planning and a mini-split isn't the right unit to use.  If the church isn't kept at regular temps constantly, a furnace that puts out craploads of heat for the length of Sunday service is what makes sense.

I think the main heating system is kept at a low temperature most of the week. I’m in a cold climate and there are fewer activities going on inside church over the last two years.

So it makes sense to use supplemental heat on Sunday morning, I just didn’t understand why cold air was blowing on me.

We kept the doors and windows open until mid November for better air circulation, but now we’ve got fancy air cleaners and a special CO2 monitor.

Our previous church was a Victorian stone pile that was horrible to heat and we wore coats and gloves and took a blanket with us.

[BlueHouse]

I didn't see anyone else mention this: 
I have heat pump system on the top floors of my home, and things started getting very humid inside.  I eventually had to replace the system, but I was given a lot of advice that if I didn't run the unit long enough, there wasn't time to pull humidity out of the air.  So I was told for the last 2 years to allow my home to get a bit warmer during the day and then run longer to cool it o  before I returned home. 

I don't know if that mattered...like I said, I eventually got a new system and now it's great.  Also, heat pumps apparently have 1/2 the lifespan of a similar furnace because they work all year round instead of just to heat. 

[ChpBstrd]

Heat pumps are at their most efficient when they're pushing a lot of air across the coils and changing its temperature by just a few degrees. That means lots of run time and lukewarm air coming out of the ducts in winter. These would be symptoms of failure in a gas furnace, which is designed for short blasts of hot air. Thus people who go from gas furnace to HP tend to think there's something wrong. Yet - hide and watch - either keeps the house at the thermostat's temperature.

A HP will take a while to warm up a cold house or cool a hot house, unless it is oversized. It is worth it to verify that the HP is properly sized for the house because improper sizing is a huge cost driver. The cost of the energy consumed by HVAC equipment dwarfs the cost of the actual equipment, so it almost always makes sense to rip out an inefficient or improperly sized system that is running up bills.

Regarding the idea of turning the HP on and off to try to save money... would you plug in and unplug your refrigerator to do the same? Of course not. So the whole plugging/unplugging thing is working really hard to get the HP to operate outside its designed efficient zone.

OP, I suggest an HVAC service call. Have the technician check refrigerant levels and clean both the inside and outside coils. Other than fan obstructions or condensation line clogs, that's about all that could go wrong with a HP.

My HP just turned 15 and is still going strong. I spent $1600 on electricity in the past 12 mos.

[uniwelder]

Regarding the idea of turning the HP on and off to try to save money... would you plug in and unplug your refrigerator to do the same? Of course not. So the whole plugging/unplugging thing is working really hard to get the HP to operate outside its designed efficient zone.

OP, I suggest an HVAC service call. Have the technician check refrigerant levels and clean both the inside and outside coils. Other than fan obstructions or condensation line clogs, that's about all that could go wrong with a HP.

OP here.  Somehow this thread keeps getting derailed from the primary focus, which was improving efficiency, not rants about how much heat pumps suck.  Thats not focused on you, ChpBstrd, but from your comment it seems you think I fall into that camp.

I don't have any issues with my heat pump (rental property) or mini-split (primary home), but am always looking for ways to improve efficiency.  Both units are LG inverter types with no backup resistance heating and blow nice warm air.  The heating portion of the electric bill was about $120 last month for our house, which is comparable to what most people in an equivalent house would spend for natural gas in our area, but we have no natural gas line available.  I really like my units and try to convince people that new heat pumps designs don't suck--- generally the hvac technicians/salespeople do.

I question the refrigerator analogy.  If it were more portable and wasn't so heavy, it would definitely be cheaper to run if I could stick it outside at night.  Right now in winter, it wouldn't need to be running at all with freezing temps.  Inside the house, it typically only runs 25% of the time, unless you put a bunch of warm stuff inside or forget the door open.  Somehow I'd like to logically circle this back to the idea for the heat pump. 

A properly sized heat pump should run 100% of the time in the worst temperature conditions, which happen in only 1% of the lowest temps.  So on average for daytime temps, it will be oversized by probably 2-4x.  For example, in my area, the 1% lowest design temperature is 15F, and we might see a few hours of extreme lows around 5F through the winter, but more typically 20-30F overnight, and 35-45F during the afternoon.  If it would spend more time running in the day, rather than night, my guess is that it should use less energy overall.  Since it would be greatly oversized for typical daytime temps, I think it should easily get the house back up 5 degrees or so running for a few hours before everyone gets back home from work/school. 

My guess was that running at 100% capacity for a few hours in the most ideal outdoor temperature should have the unit running at optimal efficiency, but that could be wrong.  I'd like to hear a better argument as to why, and more importantly, where the sweet spot is.  It might be something like running at 50% capacity, in which case, can a smart thermostat be programmed to run the heat pump at its optimal output and can it calculate what that is? 

[Papa bear]

I think I've heard that there are heat pump water heaters now.  I wonder how they can heat water to a comfortable temp?  Maybe we should all just buy one of those & connect it to radiators...

I’m one of the people up thread that was hating on heat pumps.  And I guess I wasn’t entirely truthful. I am the owner of a heat pump hot water tank. I find the unit to be more than adequate for my residential hot water needs. It has no problem taking the temp up to 125F.  It also has the added benefit of keeping my basement dryer, as it does pull moisture out of the surrounding air.   

The only company I’ve found that will do air source heat pump for radiant heat is the Sanco system.  The issue with the air source heat pumps for radiant heat is that the typical normal water temperature for this is around 180F. I believe it’s difficult for the heat pump to get that kind of temperature delta over your incoming water, so those sanco systems I believe are only rated for 10k btu of heating and less.  Not really enough to handle an entire house heating needs. 


Sent from my iPhone using Tapatalk

[uniwelder]

I didn't see anyone else mention this: 
I have heat pump system on the top floors of my home, and things started getting very humid inside.  I eventually had to replace the system, but I was given a lot of advice that if I didn't run the unit long enough, there wasn't time to pull humidity out of the air.  So I was told for the last 2 years to allow my home to get a bit warmer during the day and then run longer to cool it o  before I returned home. 

I don't know if that mattered...like I said, I eventually got a new system and now it's great.  Also, heat pumps apparently have 1/2 the lifespan of a similar furnace because they work all year round instead of just to heat.

I think that happens when the unit is oversized.  If your new unit fixed the problem, is it because its a smaller size or because its 2 stage or variable speed?

[uniwelder]

I think I've heard that there are heat pump water heaters now.  I wonder how they can heat water to a comfortable temp?  Maybe we should all just buy one of those & connect it to radiators...

I’m one of the people up thread that was hating on heat pumps.  And I guess I wasn’t entirely truthful. I am the owner of a heat pump hot water tank. I find the unit to be more than adequate for my residential hot water needs. It has no problem taking the temp up to 125F.  It also has the added benefit of keeping my basement dryer, as it does pull moisture out of the surrounding air.   

The only company I’ve found that will do air source heat pump for radiant heat is the Sanco system.  The issue with the air source heat pumps for radiant heat is that the typical normal water temperature for this is around 180F. I believe it’s difficult for the heat pump to get that kind of temperature delta over your incoming water, so those sanco systems I believe are only rated for 10k btu of heating and less.  Not really enough to handle an entire house heating needs. 

For in-floor heating, water temp doesn't need to be any more than 120F.  If cast in concrete, I don't think the water temp is generally supposed to be over 100F.  For those applications, an air to water heat pump would be great.  If you're trying to use it for baseboard heat or radiators, then no.

[ChpBstrd]

A properly sized heat pump should run 100% of the time in the worst temperature conditions, which happen in only 1% of the lowest temps.  So on average for daytime temps, it will be oversized by probably 2-4x.  For example, in my area, the 1% lowest design temperature is 15F, and we might see a few hours of extreme lows around 5F through the winter, but more typically 20-30F overnight, and 35-45F during the afternoon.  If it would spend more time running in the day, rather than night, my guess is that it should use less energy overall.  Since it would be greatly oversized for typical daytime temps, I think it should easily get the house back up 5 degrees or so running for a few hours before everyone gets back home from work/school. 

My guess was that running at 100% capacity for a few hours in the most ideal outdoor temperature should have the unit running at optimal efficiency, but that could be wrong.  I'd like to hear a better argument as to why, and more importantly, where the sweet spot is.  It might be something like running at 50% capacity, in which case, can a smart thermostat be programmed to run the heat pump at its optimal output and can it calculate what that is?

I see what you mean. My understanding is that short cycles of running are less efficient than steady running, so on those semi-nice days when the unit only needs to apply maybe 15% of its capacity, it'll be on and off maybe 10 minutes every hour.

One solution would be to allow for wider temperature swings. E.g. on a 50F day, you let the house get down to 65F before the heat comes on, and then warm it up to 75F, and then stay off for the next 4 hours. This plan might have comfort and humidity consequences, and it's not clear if you'd save any energy because the house's energy losses would accelerate during the times the house temperature was much higher than the outdoors, only partially offset by the slower losses when the house was colder.

A better solution might be to have two small HPs instead of one large HP, for example a couple of mini-splits instead of a single central forced air unit. You'd only run both at the same time on cold or hot days. The rest of the time (probably the majority of the time) you'd only run one of the small HPs, and it would have to run longer cycles in order to keep up with the house that is too big for it.

Other than that all you can do is keep the coils clean and do checkups to ensure the refrigerant level is correct.

[BlueHouse]

I didn't see anyone else mention this: 
I have heat pump system on the top floors of my home, and things started getting very humid inside.  I eventually had to replace the system, but I was given a lot of advice that if I didn't run the unit long enough, there wasn't time to pull humidity out of the air.  So I was told for the last 2 years to allow my home to get a bit warmer during the day and then run longer to cool it o  before I returned home. 

I don't know if that mattered...like I said, I eventually got a new system and now it's great.  Also, heat pumps apparently have 1/2 the lifespan of a similar furnace because they work all year round instead of just to heat.

I think that happens when the unit is oversized.  If your new unit fixed the problem, is it because its a smaller size or because its 2 stage or variable speed?

I had read (on this site) about that being a possible condition and I brought it up to my HVAC contractor, who didn't seem to think it made much of a difference -- until I told him that I consulted an HVAC expert that I happened to work with.  He looked into it and found that my house is a few hundred SF smaller than some of the other homes (we're all pretty much the same with a difference of one foot of width across 4 floors).  So while maybe it didn't make a difference, he did give me a smaller unit (and I saved a few hundred dollars because of that). 
One of my neighbors said that the "too big unit" actually caused condensation on the ductwork which wasn't sized properly.  Some neighbors have had ceilings ripped out for new ducts, mold issues, etc. 
It's hard to say if that's what made the difference.  The first 5-6 years in the house the AC worked great -- no issues.  But the 7&8 years, I could hear the unit short-cycling in the mornings as I lie in bed.  And by short cycling (another term I learned here), I mean the AC fan turned on every 6-10 minutes.  The air itself only stayed on for 4-5 minutes.  By the time I finally made the call to fix the heat pump, the system wasn't retaining any freon at all -- so I don't know. 
I seem unable to grasp how these things work even after having them explained to me. 

[KarefulKactus15]

I didn't see anyone else mention this: 
I have heat pump system on the top floors of my home, and things started getting very humid inside.  I eventually had to replace the system, but I was given a lot of advice that if I didn't run the unit long enough, there wasn't time to pull humidity out of the air.  So I was told for the last 2 years to allow my home to get a bit warmer during the day and then run longer to cool it o  before I returned home. 

I don't know if that mattered...like I said, I eventually got a new system and now it's great.  Also, heat pumps apparently have 1/2 the lifespan of a similar furnace because they work all year round instead of just to heat.

A frightening amount of HVAC contractors don't....or worse can't, do the correct math the size a unit for a home.

So we end of with AC units that are 40-60% oversized "just to be safe". And gas furnaces that are often 2x oversized!

With the oversized ac you will short cycle the equipment. It takes about 5 mins for an AC system to reach peak efficiency, so you constantly run at sub optimal conditions. Also starting the equipment has the highest wear on the compressor windings, so that will fail sooner also.  (Think of compressor life being rated in total starts more so than actual run time)  On top of all that, you get to live with humidity problems as the short run times on a humid spring day won't do shit for removal of humidity. 

On the furnace, if it can heat your house in 10 minutes, it's oversized. This will lead to strong temperature swings and poor air mixing.  This is especially apparent in multi story applications. One floor will be 4-6 degrees different in temp.


Which brings me to my next point - because calculations aren't done the ductwork often isn't balanced correct. Delivered heating btu and cooling btu are supposed to be within 20% of each other.... But they aren't.  So you have rooms that have comfort problems depending on the season.

My vote for the perfect system in my climate zone 3 is dual stage.  You get 65% output for the shoulder days and 100% when you really need it.       Gas + ac vs heat pump - depends on what infrastructure you have in place - stick with it.  However I think gas + ac represents a better long term value atm.