Energy used by cooking

Last update: June 2013

Natural Gas vs. Electric:  Which is cheaper?

Natural gas is almost always cheaper than electricity.  Of course, if you don't cook very much, the savings won't be that great.  Electric stoves account for only 2.8% of electric use for households that have them.  (The oven part of the stoves comprises only 1.8%.) (DOE, 2001)  The calculator at right will help you find which is cheaper for your own particular situation, according to how much you cook and your local fuel rates.

Note that if you don't already have gas lines in your home then you'd have to pay to have them installed, which could easily cost hundreds of dollars.  And when you sign up for gas service, you'll pay ~$12/mo. for the privilege of being a customer of the gas company, no matter how little gas you actually use.  You'll need to weigh these costs against the savings the calculator shows for switching from electric to gas.

Regardless of which is cheaper, gas presents two special problems, which is why I don't use gas in my own home even though it's cheaper:

1. Gas means a risk of explosion.  Having a gas line in your home means that it's much more likely to accidentally explode.  True, most people's kitchens don't blow up, but some of them certainly do.
   
   
2. Gas means air pollution.  The combustion of gas produces poisons in indoor air.  The problem with air pollution from gas ovens/stoves is so bad that I found this in a Whirlpool oven manual from 2003: "The health of some birds is extremely sensitive to the fumes given off [by the oven]. Exposure to the fumes may result in death to certain birds. Always move birds to another closed and well ventilated room."  While the problem is more serious for birds it exists for people, too.  A study commissioned by the Air Resources Board of California showed that gas ovens generate unhealthy levels of combustion byproducts like carbon monoxide and nitrogen dioxide.  (It also showed that the self-cleaning mode generated a lot of indoor air pollution, whether it was a gas or an electric oven.)  If you do use gas, the Children's Health Environmental Coalition has a list of ways to reduce gas pollution in your home.

Also note that if you're trying to save energy for environmental reasons (rather than saving money), then what you eat is more important than how you cook it.  For example, meat requires tremendous amounts of energy to produce, so substituting more vegetables, beans, and grains lowers your energy footprint dramatically.  It takes 68 times more fossil fuel to produce beef than potatoes, for example. (source)   Trying to figure out the most energy-efficient way to cook meat is like trying to figure out the optimal speed to drive a huge SUV for the best fuel economy.  Meatless meals require far less overall energy, every time. (more...)

Tips to save on energy and costs when cooking

• Use a solar oven.  This is the main way of cooking in Mr. Electricity's household.  It's remarkably easy to use and gets plenty hot — 300-350°F.  And somehow foods don't seem to burn.  We can put something in the oven and then even if we forget about it for hours, it's just fine later.  The unit pictured is the $260 Global Sun Oven.  The payback time for me was about ten years, but you know what?  I've owned mine for 13.  Also, my goal with saving energy isn't just to save money, it's to reduce my pollution footprint by consuming less resources.  Finally, this thing is just plain fun to use.
  
  Another company makes a bigger version that fits two pots side by side, and it's actually a little cheaper, than the model pictured, but it doesn't get quite as hot, and it's not nearly as convenient.  (You have to do a lot of fiddling with the mirrored panels to set it up and to shut it down.)  I know because I own one of each.
  
  
• Use a crockpot or a microwave oven for baking.  Besides a sun oven, these are the cheapest ways to bake.
  
  
• Open the oven door only when necessary. Oven temperature drops 25-30 degrees every time you open the door. Getting an oven with an oven light and a glass window in the door will let you check on your food without opening the door.
  
  
• Don't put aluminum foil on the bottom of a gas oven to catch drippings. The foil blocks the heat that the oven is trying to produce. (It's fine to put foil in an electric oven, as long as you leave the heating elements on the side exposed.)
  
  
• Use glass and ceramic pans when baking. They retain heat better than metal pans and allow you to lower the baking temperature by 25 degrees.
  
  
• Isolate the kitchen. If the oven is on for an hour or more, close doors leading to the kitchen to keep the kitchen from heating up the rest of the house.  If you have a stove exhaust fan, use it.
  
  
• Don't use pilot lights on gas burners. Pilot lights not only waste gas Cost24/7, they add heat to your home. Eliminating pilot lights means lower costs for cooling since you'll run the A/C less. Going pilotless will use 40% less gas than normal. (source)  If your existing stove already has pilot lights, turn them off and use a clicker-lighter to light the burner when you're cooking.  (Turning them off requires tightening the set screw. You can't just blow the pilot out, because then gas will still leak out the unlit pilot hole.)
  
• Stovetop vs. microwave is about the same.  While microwaves are more efficient than oven-baking, they're slightly less efficient than stovetop cooking, though the difference is so small it doesn't really matter which you use. (Home Energy)
  
  
• Remember that if your goal is to save energy for environmental reasons, the real savings is by substituting vegetarian foods for meat, not by changing your cooking methods.  It takes 68 times more energy to produce beef than to produce potatoes. (more...)

The cost of baking methods compared

The table at right shows how different baking methods stack up.  I suspect that the figure for electric ovens might be too high. I'll measure the actual use of an oven some time and report it here.

Note from the second row in the table that gas ovens use electricity!  Electric ignition ovens run a 350-watt glow bar to keep the gas flame going. (more...)

APS has a good table showing the efficiency of gas, electric, and microwave ovens. The efficiency doesn't tell you the cost, though, because different energy sources are charged at different rates.

Note that for someone baking three hours a week, the cheapest baking method saves only $2.61/mo. compared to the most expensive method.  This underscores my point that focusing on cooking methods is not the way to save electricity, and you should look at heating, cooling, lighting, and laundry instead.

Induction stoves:  Very efficient but super-expensive

Induction stoves cook by heating the pot or pan directly.  Oh, you thought that's what your current stove does?  No, a regular stove starts with the heat elsewhere which is then transfered to the pot or pan.  An induction stove doesn't transfer the heat to the cookware, it heats the cookware directly.  Think of your cookware as having an invisible "on/off" switch that your stove knows how to activate.

Doesn't that just seem like magic or something?  I could explain how that works, but let's not spoil the mystery.

Anyway, since it heats the cookware directly, induction cooking is more efficient—as you might expect.  An induction stove uses a whopping 30% less energy than a regular electric stove.  (It doesn't save anything on the oven, though, just the stovetop.)  But keep your panties on, because the cheapest induction stove you can buy is $1300.  If you use all four burners for half an hour a day on medium, five days a week, it will take only about 42 years to pay for itself.  Congratulations.  Oh, and did I mention that you can use only ferrous (iron or steel) cookware?  Aluminum and copper won't work, so you might be looking at buying new cookware.

Now, there are other reasons you might like an induction stove.  So here's the big list of possible pros:

• It's magic!  Okay, it's not really magic, but as Arthur Clarke said, any sufficiently advanced technology is indistinguishable from magic.
  
• You get the instant change of temperature that you'd get with a gas stove, but without the fumes.
• It doesn't add extra heat to your home, since all of the heat used is for cooking, with no extra wasted.
  
• The cooktop cools down very fast when you turn it off—about four times faster than a conventional cooktop. 
  
• The surface is flat and seamless, so it's easy to clean (although many electric stovetops offer the same convenience).
• It does save energy, if being green is more important to you than a really high price.

For more than you ever wanted to know about induction ovens, see The Induction Site and this article in Popular Mechanics.

Efficiency: probably not what you're thinking

Most people who ask me which fuel source is "most efficient" have it backwards:  They actually want to know what's cheapest.  But efficiency and cost are not the same thing.  Efficiency is what percentage of a fuel goes towards doing work.  Electric ranges are a lot more efficient than gas, but gas is very cheap, so overall it's usually cheaper to use gas even though it's not as efficient as electric.

Energy used by electric ovens

The specs I've seen for electric ovens have a bake element of 2000 to 3500 watts with a maximum temperature of 500-550° F.  However, different ovens should use about the same amount of energy to come up to and maintain a given temperature setting.  My feeling is that the higher-wattage ovens simply get up to the desired temperature faster, but don't take any more energy to do so.

And whether the oven is high-wattage or low wattage, it's rare for the bake element to run continuously at full capacity. It either runs at a lower power level or shuts itself off for a few minutes at a time in order to maintain the desired temperature.

Estimates I've seen elsewhere for an electric oven set to 350° is 2.0 kWh per hour, regardless of the wattage of the bake element. I suspect that this might be a bit high, and I'll do a direct measurement myself when I have time. (I did measure consumption in a toaster oven at 350° and it used only 0.33 kWh in an hour.) In the meantime, if you're using the 2.0 kWh figure for an oven, adjust up or down for higher or lower temperatures.

Broil elements are rated higher than bake elements, typically 3000 to 3600 watts. However, it's unlikely that they run continuously to maintain temperature, so I think a figure of 2400 watt-hours per hour is a more reasonable figure to use while broiling.

Self-cleaning ovens use energy at a much higher rate when cleaning, because they get much hotter than they do for cooking.  I couldn't find any reliable figures for the rate, but the Department of Energy says that an oven uses about 5.3 kWh per cleaning cycle. (DOE, PDF)

For more raw data about the energy used by cooking appliances (not just electric), see this 340-page PDF report by the Dept. of Energy.

Below are questions I've received and answered about how saving energy when cooking.

Questions and comments about saving energy when cooking

When my wife wants a cup of hot water she heats up a cup of cold water in the microwave.  I keep telling her that it is uses less power from a financial standpoint to heat the water in a teapot on our gas stove.  She doesn't believe me.  Who is right? -- Anonymous

Which uses less electricity: boiling water with an electric burner or boiling it in a microwave oven? -- Anonymous

There is no such thing as "less power from a financial standpoint".  There is either "less energy" or "lower cost", which are two different things.  So first you need to decide which one you want to argue with your wife about.

Anyway, for all intents and purposes the energy used between a microwave and an electric burner is the same.  I boiled two cups of 86-degree water in a GE microwave oven (Model JS1533BV001, 1995) and it used 0.087 kWh.  Boiling it in a pot on an electric burner used 0.095 kWh.  While there's a difference it's not statistically significant, especially given how crude my testing methods were.  Even assuming that these figures are completely accurate, then boiling two cups of water every day for a year would use only 2.92 kWh extra with the electric burner, or less than $0.30 for the whole year.  Clearly obsessing over which method you use to you boil water is not worth your time.

The story isn't much different for a gas stove. According to Home Energy Magazine, gas stoves are only 40% efficient compared to a microwave's 55%. But the gas stove is usually cheaper to run because gas is usually a lot cheaper than electricity. The microwave uses less energy, but the gas stove is cheaper financially.  Though again, we're splitting hairs, because we're talking about pennies of difference a year.

Note that if you boil 3 cups of water in a kettle when you need only 1 cup for tea, you've used 3 times as much energy as you needed to.  Again, we're talking about pennies, but if you really want to save, making sure you boil only as much as you need is far more important than which heating method you choose.

Tom Murphy found that an electric kettle uses the least amount of energy, but again, if your kettle has more than the cup of water you actually need, then heating the extra water easily erases the savings.

Please remember that the heating method you choose doesn't really make much difference.  Compared to choosing the best method to heat water, you'd save more energy over the year by replacing one light bulb with a CFL or turning off the air conditioner for an hour.  (Not an hour a day, one hour at some point over the whole year.)

[Note: Since I originally answered this question, a reader pointed us to Home Energy Magazine's report on boiling water using various methods, which says that electric burners use 25% less electricity than microwaves, though again, this isn't enough to make any practical difference for most people. And again, if you boil only a mug of water in the microwave vs. a whole kettle on the stovetop, the microwave is going to be cheaper. Again, this is academic, because the difference between one method vs. the other pales in significance to the savings you'd get by using CFL light bulbs or turning off your AC for a day.]

In gas ovens with standing pilots, the pilots really are only a waste if you are running air conditioning to pump heat out of your house.  Most of the year the heat just goes into making the home warmer. — Roger S.

Yes, and unused heat is a waste.  Whether your home is 72°, 77°, or 81°F, if you're not using the heat from your pilots, then all of that energy is a waste — whether you're using air conditioning or not.  Now, during those times when you're using a heater, then yes, the pilots aren't a waste because they contribute heat that you're actually using, but nobody runs their heater 24/7 for 12 months out of the year.  (Anyone in that severe a climate has bigger energy problems then whether their stove has pilot lights.)  So when you get down to it, pilots are definitely a waste for everyone most of the time.  Nitpicking doesn't help anybody.

I won't believe this until I see some hard numbers, and I couldn't find any, even though I looked pretty hard.  The EPA doesn't even bother to rate home ovens for efficiency, which ought to tell us something.  (They don't rate clothes dryers either, because the differences between models is so negligible.)  There are also no published specs anywhere that I can find for the supposed efficiency of self-cleaning ovens, which also should tell us something.  Even if a self-cleaning oven saves a whopping 20% over a non-self-cleaning model (which I seriously doubt), we're talking about fifty cents a month difference for two hours a week of use.  Finally, if you ever actually use the self-cleaning feature, then you blow a whopping 5.3 kWh per cleaning, which will likely erase any savings from the greater insulation, and then some.