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Learning, Sharing, and Teaching => Ask a Mustachian => Topic started by: CheapScholar on August 24, 2019, 02:21:32 PM

Title: Energy efficiency (cooking)
Post by: CheapScholar on August 24, 2019, 02:21:32 PM
Anyone ever look into energy efficiency when cooking?  Specifically, Iím wondering which is generally cheaper, a crock pot or gas oven.  Obviously basking in an oven generally takes less time, so the fair comparison is probably 6 hours of crock pot use on low vs. gas oven for 60-90 minutes.

I donít happen to know my local usage rates for electricity or gas, but wondering if others have explored the topic generally.
Title: Re: Energy efficiency (cooking)
Post by: GizmoTX on August 24, 2019, 02:30:52 PM
Use a pressure cooker, electric or stovetop. Much more energy efficient, faster, & tastes better than in a crockpot. A crockpot will be more efficient than an oven, gas or electric, & heat the kitchen less.
Title: Re: Energy efficiency (cooking)
Post by: nereo on August 24, 2019, 06:46:35 PM
It also matters a great deal if it is summer or winter.  In winter the total energy cost will be very close to zero, as heat from whatever source you are using will result in an equal reduction in your heating costs. This of course assumes you live in a cold climate and donít have an exhaust fan running

But yes, a pressure cooker will use the least amount of energy all else being equal
Residential ovens are designed to vent, so they tend to be the most energy intensive

Title: Re: Energy efficiency (cooking)
Post by: deborah on August 24, 2019, 07:07:15 PM
Microwave ovens are the best.
Title: Re: Energy efficiency (cooking)
Post by: CheapScholar on August 24, 2019, 07:13:44 PM
Good point about about the weather factor.  I live in the upper Midwest so very cold winters and very hot summers. 

My house has an outdoor grill with the gas pipeline feeding it so I grill when itís hot out.  I do use the gas oven on very cold days.  But Iím thinking about fall coming when I hardly use the AC or furnace and the oven being on wouldnít necessarily make the house uncomfortable.  I assume the crockpot is much more efficient than my gas oven in that situation.  I should look into pressure cookers but the last thing I need in my kitchen is another thing taking space.

I agree the microwave is probably the best in terms of efficiency but I doubt my wife would get excited about any dinner I make in the microwave.
Title: Re: Energy efficiency (cooking)
Post by: Goldielocks on August 24, 2019, 07:17:59 PM

I agree the microwave is probably the best in terms of efficiency but I doubt my wife would get excited about any dinner I make in the microwave.
Microwaves can be better a lot better than the pressure cooker.  PC's do a nice pot roast, potatoes, boiled foods.   Microwaves do a good meatloaf, vegetables, rice and even a cake / brownie.
Title: Re: Energy efficiency (cooking)
Post by: Cadman on August 24, 2019, 07:23:20 PM
Yep, microwave and induction are the most efficient, followed by electric and then gas (~50%). But as pointed out, in a cold climate that waste-heat ends up being useful.

In the winter, I use my trusty electric range, but in the summer, I have an air fryer and induction hotplate that don't heat the whole place up. Matching pot size to element size, or adjusting element size electrically (some cooktops feature this) will help.

I've also got a 1970 GE Range that looks completely conventional but has a little secret. The oven is also a microwave. You can use conventional baking/broiling elements and add in MW power to cut cooking time in half with the same results you'd get with a regular oven. Enthusiasts swear by them.
Title: Re: Energy efficiency (cooking)
Post by: Cranky on August 25, 2019, 05:57:05 AM
Crockpots don't use a lot of electricity, from what I've seen, and I know that there are charts out there.

But much depends on the relative cost of your gas and electric, plus how much you are cooking. If you can get multiple things into your oven at once, that is more efficient.

But looking at my natural gas bill, the main expense is running the furnace in the winter, and then the hot water heater. Cooking is about $5/month.

Title: Re: Energy efficiency (cooking)
Post by: NorCal on August 25, 2019, 11:28:20 AM
I remember looking into this a number of years ago.  While I don't remember the specifics, I do recall that cooking uses a pretty small percent of household energy (I think sub 5%) in total. 

I also recall that while certain methods of cooking can be somewhat more efficient (induction vs. gas vs. electric), the difference between their efficiency is so small that you wouldn't notice it in your bills.  I was only comparing ovens/cooktops, and not thinking of crock pots at the time.

I would imagine that crock pots use significantly more energy, just because they run for so long.

I'd be curious in feedback if you actually did the math.  The right way to calculate it would be to try and approximate your cost / hour of running the oven vs. crock pot.
Title: Re: Energy efficiency (cooking)
Post by: Christof on August 25, 2019, 03:16:35 PM
Yes, I did calculate this. We pay six times as much for electricity than for gas, so gas wins for us, even with the crockpot being more efficient. The most inefficient way to cook food is in our electric oven, though. In summer one and a half our of baking in the oven is about the same as our daily electricity use for everything else (4.5 kWh). We use gas for heating water, so hot water is not included in these numbers.
Title: Re: Energy efficiency (cooking)
Post by: GeneralJinjur on August 25, 2019, 03:59:11 PM
I expected this to be a discussion of solar cooking.  I bought a used solar oven several years ago and we use it to cook in our suburban backyard through the summer.  We have played with it in the cooler months, but the fences and the low sun angle limit our cooking time too severely.  It is a truly odd experience to step out the back door and smell a casserole cooking!  I like using it for baking cakes, casseroles and roasting chicken or veggies.  It's like nature's crock pot in that it is fairly difficult to burn a meal.
Title: Re: Energy efficiency (cooking)
Post by: Prairie Stash on August 27, 2019, 02:33:10 PM
Cost - gas oven is cheaper
Uses overall less energy - tough to say, I bet oven because most crock pots apply continuous energy to compensate for their weak insulation. Look at the wall thickness of your oven compared to your crockpot.
Climate change - gas is generally better than Electric, much of the continental interior power grid uses Coal to make electricity. If you were all solar panels, then I would say electric.

Put an electric meter on the crockpot and you'll get an answer on how much it costs to cook that pot roast. Then, if you're like me, record the gas meter before/after cooking something.

In case its interesting, my gas hot water tank uses about $5/month in gas, that's for heating water for showers/baths/dishwashing. You generally pay more for gas installation and appliances (upfront costs) but operational costs are lower. An electric tank would run $30/month to operate (approximately) but I could have had it for $250 less when I replaced my last tank.
Title: Re: Energy efficiency (cooking)
Post by: Cadman on August 27, 2019, 08:28:34 PM
Hey Prairie Stash, it's the other way-round. Insulation is much better on the crock pot than today's gas ovens, and most "gas" ranges are set up as gas cook tops with electric ovens due to the difficulty in maintaining even baking with gas. Of course gas cooktops suck for efficiency, but are quite responsive.

Now, if we we're talking an early 50's Maytag 'dutch oven' it'd be a different story. These were heavily insulated and designed to burn gas to bring the entire chamber up to temp. You'd then switch it off and bake a few hours without any additional heating. Late 40's, early 50's energy wasn't as cheap as we think it was and appliances were designed for efficiency up to around 1960 when rates started dropping and features started to dominate marketing instead.

Gas water-heating is a different matter; if you dont' have PV solar, then gas is superior in this application.
Title: Re: Energy efficiency (cooking)
Post by: lutorm on August 28, 2019, 12:38:10 AM
I recently installed a "Curb" energy monitor and from this I know that our electric (induction) range+oven uses < 10% of our total electricity. It uses a lot of power when you're heating something but that's for a short time. It's not really enough to worry about, imho.

The water heater is a different issue altogether. I'm very interested in the heat pump water heaters that exist now, does anyone have experience with them?
Title: Re: Energy efficiency (cooking)
Post by: Christof on August 28, 2019, 05:04:52 PM
That is interesting. Our oven easily uses 2-4kWH per use, less for the range. Compared to out total usage of 6.5kWh on average, itĎs a significant part for us.
Title: Re: Energy efficiency (cooking)
Post by: Chickadee on August 29, 2019, 03:11:05 PM
 The most efficient move you can probably make is to go ahead and cook everything for a segment of time at once.

When I heat up the oven I make sure that I go ahead and fill it up, that means getting tomorrowís dinner in there if I can. This is especially easy with baked main dishes where you can make todayís dinner and tomorrowís dinner.

 I know a lot of people donít like leftovers but I really donít mind popping a lid on a casserole dish and put it in the fridge overnight to save the proper time, cleanup time, and the waiting time of the oven not to mention the energy consumed by doing it on one day instead of two.

 I sort of do the same thing even if Iím just putting together a fruit tray, itís a lot easier to go ahead and get together a Tupperware and make a second small fruit tray to take to work for my snack the next day. Human energy saving!
Title: Re: Energy efficiency (cooking)
Post by: Prairie Stash on August 29, 2019, 06:08:50 PM
Hey Prairie Stash, it's the other way-round. Insulation is much better on the crock pot than today's gas ovens, and most "gas" ranges are set up as gas cook tops with electric ovens due to the difficulty in maintaining even baking with gas. Of course gas cooktops suck for efficiency, but are quite responsive.

Now, if we we're talking an early 50's Maytag 'dutch oven' it'd be a different story. These were heavily insulated and designed to burn gas to bring the entire chamber up to temp. You'd then switch it off and bake a few hours without any additional heating. Late 40's, early 50's energy wasn't as cheap as we think it was and appliances were designed for efficiency up to around 1960 when rates started dropping and features started to dominate marketing instead.

Gas water-heating is a different matter; if you dont' have PV solar, then gas is superior in this application.
I have very limited experience with gas ovens, it was a wild guess. So I dug deeper and found this site:
http://mindofthemother.blogspot.com/2011/03/crock-pot-energy-efficient-dream.html

From there it says, it depends on how you cook.

As for the insulation, I forgot to account for the lower temperature of the crock pot. Lower temp and less insulation in the crock vs. Higher temp and higher temp in the oven (standard oven use when roasting). So, if you cook in the oven at a lower temp (mimicking a crock pot) the gas oven is cheaper; cause a typical oven has more insulation than a crock pot. What makes them lose heat is the higher temperatures, heat loss is a function of the temperature differential and the insulation, you're right the crock pot can lose less energy, at lower temperatures, but that doesn't mean better insulation.

If you wanted to save money, use your gas oven as a crock pot. You can cook, with an oven, the same way as you cook with a crock pot (long and low). That's the lowest energy usage, it utilizes the lower energy of lower temperatures (crock pot style) with the ovens superior insulation.

We use our oven as a dehydrator, super low temp, it consumes far less energy then if you're roasting meat. That's the problem with the comparisons, it doesn't account for cooking style differences. There's no way my fruit leather is consuming the same energy as my fish sticks (per hour), since they cook/dry at different temperatures.

No simple answer, cooking style is key. Not all food tastes the same cooked in the wrong style (roasting vs. simmering).
Title: Re: Energy efficiency (cooking)
Post by: deborah on August 29, 2019, 06:43:52 PM
Of course, a hay box is the most efficient.
Title: Re: Energy efficiency (cooking)
Post by: norajean on August 30, 2019, 05:28:01 AM
The biggest impact might be cooking the largest batches you possibly can and also reducing the Fraction of cooked food you consume. Beyond that, you really need to know the actual consumption of the alternatives and your local electricity and gas costs.
Title: Re: Energy efficiency (cooking)
Post by: rivendale on August 31, 2019, 06:26:17 AM
I recently installed a "Curb" energy monitor and from this I know that our electric (induction) range+oven uses < 10% of our total electricity. It uses a lot of power when you're heating something but that's for a short time. It's not really enough to worry about, imho.

The water heater is a different issue altogether. I'm very interested in the heat pump water heaters that exist now, does anyone have experience with them?

We are all electric for heating. In December we bought a Rheem electric heat pump water heater and have had seen a considerable decrease in our energy use. Roughly $40-50 a month savings. Our kWh rate is HCOL. I wish we would have switched years ago. The unit normally costs around $1200 however Lowes had it marked down to $500, and our electric company had a $200 rebate. It's already paid for itself. On a secondary note, it helps to keep the garage much cooler.
Title: Re: Energy efficiency (cooking)
Post by: Cadman on August 31, 2019, 12:43:21 PM

I have very limited experience with gas ovens, it was a wild guess. So I dug deeper and found this site:
http://mindofthemother.blogspot.com/2011/03/crock-pot-energy-efficient-dream.html

From there it says, it depends on how you cook.

As for the insulation, I forgot to account for the lower temperature of the crock pot. Lower temp and less insulation in the crock vs. Higher temp and higher temp in the oven (standard oven use when roasting). So, if you cook in the oven at a lower temp (mimicking a crock pot) the gas oven is cheaper; cause a typical oven has more insulation than a crock pot. What makes them lose heat is the higher temperatures, heat loss is a function of the temperature differential and the insulation, you're right the crock pot can lose less energy, at lower temperatures, but that doesn't mean better insulation.

If you wanted to save money, use your gas oven as a crock pot. You can cook, with an oven, the same way as you cook with a crock pot (long and low). That's the lowest energy usage, it utilizes the lower energy of lower temperatures (crock pot style) with the ovens superior insulation.

We use our oven as a dehydrator, super low temp, it consumes far less energy then if you're roasting meat. That's the problem with the comparisons, it doesn't account for cooking style differences. There's no way my fruit leather is consuming the same energy as my fish sticks (per hour), since they cook/dry at different temperatures.

No simple answer, cooking style is key. Not all food tastes the same cooked in the wrong style (roasting vs. simmering).

That blogger is a little disingenuous though. She tacks on a 33% penalty for EL and then neglects the heat transfer loss to the gas stovetop, which is huge.  The other problem is that gas ovens are generally poor performers at low temps because you can only modulate a flame down so far before it goes out, so you end up with temperature swings as the flame is lit and extinguished making it very difficult to get baking as even as a resistive element.

But one thing that hadn't crossed my mind is how cheaply constructed today's crock pots/slow roasters are. Anyone seriously interested in crock pot cooking should hit up their goodwill for a nice pre-'80's model.