Affordable Backup Power Generator Options

[Roots&Wings]

Getting ready for hurricane season, and trying to figure out best backup power options for critical loads (refrigerator, dehumidifier, possibly a small window AC unit) which total ~1,800 watts, 15 amps. I'd like to avoid a stand alone gas generator.

A few options:
- Car power inverter, e.g. https://www.homedepot.com/p/BESTEK-12-Volt-DC-to-AC-2000-Watt-Power-Inverter-MRI20011/309970068 for $124. Hookup to car battery and idle car outside. Car alternator will produce 40 amps idling and consumes about 1/5 gallon of gas per hour. Around 80 total hours run time for car's gas tank size, fridge would need to be run about 2 hrs every 6 hours, could last for 10 days without power.

- Power inverter (same 2000 watt model above) paired with deep cycle marine battery and solar panel. This route is appealing with no gas to run out, but trying to figure out details of battery size/capacity to power the load (which could get expensive) and solar panel size.

Power is usually restored within 3 days here post-hurricane, but with COVID-19 issues, they think it could be longer this year since out of state utility repair support may be limited.

If anyone has thoughts or experience with these for affordable backup power or other ideas, would appreciate any feedback.

[big_owl]

If your car alternator only produces 40A idling, that would be @12V = 480W.  You'll be draining your battery rather quickly at that rate.  I didn't see it in the specs but while the inverter can handle 2000W (likely steady state), what can it handle for an inrush current when your window unit cycles on?  In any case, I don't see running your car engine for a generator as a very good setup.

I also think you'd need some pretty big batteries to handle three days worth of fridge, AC, dehumidifier (and I'm still skeptical the inverter wouldn't trip due to motor inrush). 

Why not just buy one of those small honda suitcase generators?  We have one that we use on our fridge/freezer, though I've never tried it on an AC unit.  But maybe someone else has more experience using your desired setup than me and can chime in.


ETA I see 4600W starting listed on the page now.  Not sure how big your window unit is - if it was small enough then maybe it could handle starting that. 

[nereo]

Getting ready for hurricane season, and trying to figure out best backup power options for critical loads (refrigerator, dehumidifier, possibly a small window AC unit) which total ~1,800 watts, 15 amps. I'd like to avoid a stand alone gas generator.

we've looked at backup options because we live in a region where ice-storms can knock out power for several days, and occasionally for weeks. Because our home has propane and a pellet stove our power needs are similar to yours (~1,800W, 15amp).

Each time I check a stand-alone gas generator is by far the cheapest option  for infrequent, random power-outages which may last >24 hours. 
Battery backups require too much capacity (batteries) to be useful for multiple days.  Rigging them up to a PV array gets complicated (we have on on our roof that is grid-tied) and expensive. Car inverters can't carry that much and (as I understand it) you'd need to constantly **drive** your car in order for the alternater to regenerate a fast drain on your battery.

meanwhile, I can routinely buy a small gas-powered generator with low hours for ~$700.

From an economic standpoint there's just no beating that.

[Milspecstache]

Love your idea and you are definitely approaching from the right side of the equation:  lower your loads to a minimum then size your generator needs instead of totaling everything in the house and buying a too-large generator which is wasteful/inefficient/expensive.

My concern would be starting surge for the compressors you mention.  Maybe try this setup ahead of time before you really depend on it.
https://homeguides.sfgate.com/run-refrigerator-inverter-49672.html

Please let us know your results!

[lthenderson]

If I lived where hurricane season was a worry, I would get a generator that runs off propane and buy a used 1000 gallon propane tank to bury somewhere on the property. I know several people that have these setups and they start up automatically and shutdown when not needed anymore so other than a few second blink in electricity, one doesn't even know what is going on. My only hangup is that for me, it doesn't make financial sense since we loose electricity maybe a couple hours per year at most.

[JLee]

Your best solution here is likely a small suitcase generator.  The proposed car / alternator plan will likely result in a dead car battery and/or alternator (or a missing car, if someone decides they want to drive off with it).

I bought one of these a while back - it'll do 1600 watts sustained / 2000 watts surge. You will want to keep an eye on usage / oil change intervals, though, as they are surprisingly short. I don't recall off the top of my head but I think the WEN generator I have calls for an oil change every 40 hours of runtime.

[zolotiyeruki]

The above posters are right--a gas generator is almost certainly the way to go.  You can usually pick one up for pretty cheap used.  The inverter type are nice because they can run much quieter, but they also cost more.

We have a non-inverter one that we bought several years ago, used, shortly after hurricane season.  We paid $400, and it's a 5-6kW model.  In the decade that we've owned it, it has been needed precisely once, and not even by use!  Granted, we're no longer in SE Texas, but in the seven years we lived there, we only had to deal with the power being out for an extended period once (after Ike).

[Roots&Wings]

Thanks so much all! Figures the car battery + inverter route was too good to be true, would've ended up with a dead car and spoiled fridge. The 5k Btu window AC units use surprisingly little power (4.1 amps x 115 volts = 472 watts)

@nereo I also have grid tied solar, and it's so frustrating it would cost thousands of dollars to install a different inverter to even be able to use the power directly. The marine battery + PV panels route was also getting into the low thousands.

Already purchased a 2kW gas inverter generator (this model, new for $350 with 2 yr warranty) and was having second thoughts since I could barely lift the box, plus dealing with gas, oil changes, etc. I don't have a spot to bury a propane tank either.

Hopefully it won't be needed much. Thanks again!

[JLee]

Thanks so much all! Figures the car battery + inverter route was too good to be true, would've ended up with a dead car and spoiled fridge. The 5k Btu window AC units use surprisingly little power (4.1 amps x 115 volts = 472 watts)

@nereo I also have grid tied solar, and it's so frustrating it would cost thousands of dollars to install a different inverter to even be able to use the power directly. The marine battery + PV panels route was also getting into the low thousands.

Already purchased a 2kW gas inverter generator (this model, new for $350 with 2 yr warranty) and was having second thoughts since I could barely lift the box, plus dealing with gas, oil changes, etc. I don't have a spot to bury a propane tank either.

Hopefully it won't be needed much. Thanks again!

That seems a bit low for power on the AC unit, and it'll also have a higher startup surge -- what model is it?

[nereo]

Thanks so much all! Figures the car battery + inverter route was too good to be true, would've ended up with a dead car and spoiled fridge. The 5k Btu window AC units use surprisingly little power (4.1 amps x 115 volts = 472 watts)

@nereo I also have grid tied solar, and it's so frustrating it would cost thousands of dollars to install a different inverter to even be able to use the power directly. The marine battery + PV panels route was also getting into the low thousands.

Already purchased a 2kW gas inverter generator (this model, new for $350 with 2 yr warranty) and was having second thoughts since I could barely lift the box, plus dealing with gas, oil changes, etc. I don't have a spot to bury a propane tank either.

Hopefully it won't be needed much. Thanks again!

Yeah, about what I’ve found too
Regarding the solar array - it’s not as simple as just having a switch to throw to divert power from the grid to your home. The real complexity is managing the voltage. That and having a power source once the sun goes down or it rains (which is likely around a hurricane). So you still need a sizable battery setup with a couple dozen amp hours. I think I was quoted $3400, most of which was equipment.

Changing oil on a generator is dirt simple. Just make sure you buy a few fillers and some oil ahead of time. To move it around you might consider putting it on a simple dolly with heavy duty castors. Added bonus that it raises the engine up should you get a few inches of standing water.

[Roots&Wings]

That seems a bit low for power on the AC unit, and it'll also have a higher startup surge -- what model is it?

This is the one I used for sizing: https://www.homedepot.com/p/LG-Electronics-5000-BTU-Window-Air-Conditioner-with-Manual-Controls-LW5016/311120685 4.1 amps and 115 volts down in specs. Hopefully other 5k Btu models are similar, HD, Lowes and Walmart usually have these marked down significantly around Memorial Day. 

If nothing else, I could run the dehumidifier from the car (3.7 amps x 115 volts = 426 watts) using a $40 inverter without draining the battery. 95 degrees and 100% humidity is pretty miserable, I'd probably be fine with just the dehumidifier, and refrigerator has previously gone 3 days without spoiling (load it up before hand with frozen water jugs), but my parents might need to come over this year if we lose power and they'd be miserable without AC.

[Roots&Wings]

Yeah, about what I’ve found too
Regarding the solar array - it’s not as simple as just having a switch to throw to divert power from the grid to your home. The real complexity is managing the voltage. That and having a power source once the sun goes down or it rains (which is likely around a hurricane). So you still need a sizable battery setup with a couple dozen amp hours. I think I was quoted $3400, most of which was equipment.

Changing oil on a generator is dirt simple. Just make sure you buy a few fillers and some oil ahead of time. To move it around you might consider putting it on a simple dolly with heavy duty castors. Added bonus that it raises the engine up should you get a few inches of standing water.

Yeah, $3.4k for nominal loads is pretty hard to swallow. Powerwalls like Tesla or Generac can run $9-10k+ installed. Wholesale solar had a good overview of options for adding battery backup to grid-tie (https://www.wholesalesolar.com/blog/add-battery-backup-to-grid-tied-solar-system), but it's all pretty costly materials alone, even DIY.

That's great to hear the oil change is so simple! Yep, I ordered the oil, a 5 gallon gas can, and extension cords together with the generator, just need to unpack it all and setup. Good idea too with the dolly/casters, I've seen those out for the trash sometimes and might be able to get one free.

[Wrenchturner]

Using a car's engine for power generation is like a Rube Goldberg machine.  Also, they don't produce much power at idle, and it will likely overheat at 2k rpm if it isn't moving at all.  You're not going to run this for hours this way.

I was thinking a powerwall also.  They are expensive but I understand you can program them to offset your grid draw to the off-hours and produce a return that way.  It would also be the simplest strategy.

Portable generator is the usual strategy.