I recently came across a Yale Environment Review article that stated, “Cooking accounts for 20% of consumers’ energy use.” This percentage surprised me as I thought the energy used in food preparation was nominal. It got me thinking about appliances and their energy use.

I thought my information quest would be pretty simple if I did a Google search, but I was wrong.  I came across blogs, environmental websites, an electric power cooperative website, and even government-run environmental websites; they all got it wrong.  I’m not trying to be grandiose, but my conclusion was correct. 

If I queried, “How much energy is used by a toaster oven?”  All of the sites would say something like:

“Look at the device’s back panel for the wattage used and then multiply this number by the time in hours that the appliance was in use to find the appliance’s efficiency.  Let’s say the toaster oven’s label says it uses 1500 watts, and you bake something for 90 minutes (1.5 hours).  The energy would be 1500 x 1.5 = 2250 watt-hours of energy.”

This formula is utterly wrong, and it shocks me that so many authoritative sites use it. 

When vetting appliances for the solar-powered, all-electric kitchen in my camper van, I had to figure out how much power an appliance used to determine the size of the battery system I needed. The most significant energy draw in the van was cooking appliances that heated food, like my induction burner. I needed to know if I could practically power them with my solar/battery set-up. To do this, I used a Kill-A-Watt meter.  This device plugs between the appliance’s power cord and the wall outlet. It provides a wealth of information, including the watts the appliance uses at any moment and the total amount of watts/hours used for a given period measured in kilowatt-hours (kWh).  

I knew that an appliance’s actual wattage usage is often less than stated on its back panel, and sometimes, this difference can be substantial. I also knew many appliances don’t continuously operate at full power.  Many devices that heat up use a thermostat or other sensor to control the power output.  For example, my van’s induction burner is rated at 1800 watts, but it has never drawn more than 1500 watts, and at lower power levels, it only draws 600 watts intermittently.  

I continued my search and found YouTube videos that measured the power used instead of calculating theoretical numbers. The most eye-opening one was from the channel “Under the Median.”  They did a practical test cooking the same food in their wall oven, a toaster oven, a slow cooker, and an electric pressure cooker to see which was most energy efficient.  Their results surprised them, and they surprised me, too. Naturally, their wall oven used the most energy; most electric ovens use between 3 and 5 kilowatts when the heating element is on.  They were using their personal appliances, and due to a malfunction, a given appliance may have been using more power than it should. However, per their results, their toaster oven was more energy efficient than their crock pot.  What!  I had to investigate further. 

Our toaster oven is a Ninja Foodie with a stated wattage of 1800 watts. It is relatively small compared to other toaster ovens, which should make it more efficient (it has less space to heat up). It also features a 60-second preheat, much less than my regular oven, which takes over 10 minutes to preheat. I did a one-hour test at a standard 350F (177C) and monitored the Foodie’s power usage using a Kill-A-Watt meter.  

If I had used the standard (and incorrect formula), I would expect that the Foodie would use 1800 watt/hour (1800 watts x 1 hour = 1800 watt/hour).  However, that was not the case.  These were my results: 

60-second preheat operating wattage = 1600 watts

Baking element on operating wattage = 1300 watts

The oven cycled between 1300 and 2 watts as the thermostat regulated the temperature. It used 1300 watts around 34% of the time; the rest of the time, it required only 2 watts (likely to power the electronics).

The toaster oven used only 340 watts in one hour, not 1800 watts! If I were to make a pot roast in the toaster oven at 350F for 3.5 hours, the standard calculation would be 1800 x 3.5 = 6300 watt/hour used. However, the oven would have actually used 340 watts x 3.5 hours = 1190 watt/hour. That is a very significant difference!

I was intrigued as my results with my toaster oven were similar to the “Under the Median” results.  The “Under the Median” video also noted a significant difference between the energy used by a slow cooker (CrockPot) and a pressure cooker (Instant Pot). I had several of these appliances.  Would my results match theirs?

Limitations of my tests.

There are dozens of electric and stovetop pressure cookers and even more slow cookers. Naturally, I couldn’t test all of them, so please take my findings as generalities. Slow cookers and pressure cookers are most cost-effective when cooking foods like a tough pot roast.  My experiment was to calculate the energy differences when cooking a pot roast.  I tested six devices, but with the price of beef, I wasn’t going to cook six pot roasts. Instead, I used 4 cups of room temperature water as my “pot roast” in each device.  

Things that can impact the energy used by a device include:

-The size/volume of the device’s cooking chamber.

-The watts used by the heating element.

-The level of insulation of the device.

-The temperature or amount of the food being cooked.

-The device’s computer’s programming, if it has one.

-Other heat losses include opening an oven door or lifting the lid on a slow cooker.

Different gadgets cook at different times; I used the following cooking times:

Slow cookers, 8 hours on low.

Electric pressure cookers (10-12 PSI), 1 hour at high pressure.

Stove top pressure cooker (15 PSI-cooks faster), 45 minutes at high pressure.

I used two different power meters and ran several cooking devices more than once.  The two meters gave similar results. 

Manual slow cookers (those with only a high/low/off switch) continuously apply power to a belt-like heating element around the pot’s base.  A heat-retaining ceramic crock sits in the base and is indirectly heated by the heating element. The pot is designed so that the heat added eventually equalizes with the heat lost, resulting in a simmer (190F-210F) at the low setting. The high setting incorporates a second heating element in many of these manual pots, resulting in a final high temperature of around 300F for that setting.  I did my tests with these pots set on low, as that is what most would do if they were cooking a pot roast.

Other devices, including newer automatic slow cookers/multi-cookers and electric pressure cookers, use a thermostat or other sensing device to regulate whether a heating element is off or on. This should be a more energy-efficient method of temperature control.

Stovetop pressure cookers operate similarly to a manual crock pot. In this case, the cook controls the heat applied to the pot, eventually finding an equilibrium point to maintain proper pressure. I did not have the equipment to measure the power used on my stovetop (hob) as it is a 220v device, so I used a 120-volt tabletop induction burner that I could measure using my Kill-A-Watt meter. I used the burner at full power to reach pressure, then turned it down to a power level of 2.5 out of 10 to maintain pressure. 

Here are my results from worst to best energy use:

These appliances are vastly more energy efficient than using an oven for simple meal preparation. We are looking at good to excellent energy efficiency. 

Fifth Place 

Seven Quart Manual CrockPot

Stated Wattage: 270 watts

Actual Wattage Use: 204 watts (continuously on)

Final Temperature of contents: 200F (93C)

Time in operation: 8 hours

Total energy used: 1.64 kWh (1640 watts)

Fourth Place

Six Quart Instant Pot Dutch Oven Multicooker (basically an automatic slow cooker)

Stated Wattage: 1500 watts

Actual Wattage Use: 886 watts (intermittently on)

Final Temperature of contents: 206F (97C)

Time in operation: 8 hours

Total energy used: 1.2 kWh (1200 watts)

Note:  The toaster oven set at 350F for 3.5 hours would have used the same energy!

Third Place

Two and a Half Quart Manual CrockPot

Stated Wattage: 75 low/150 high watts

Actual Wattage Use: 69 watts on low (continuously on)

Final Temperature of contents: 190F (88C)

Time in operation: 8 hours

Total energy used: .534 kWh (534 watts)

Second Place

Kuhn Rikon Stovetop Pressure Cooker/Duxtop Induction Burner

Stated Wattage: 1800 watts for the induction burner

Actual Wattage Use: 1443 watts to reach pressure, 600 watts intermittently to maintain pressure.

Time in operation: 45 minutes (15 PSI, cooks faster than electric pressure cookers)

Total energy used: 0.43 kWh (430 watts)

First Place Tie

Mealthy 6 Quart Electric Pressure Cooker

Stated Wattage: 1000 watts

Actual Wattage Use: 886 watts to reach pressure, then cycled to maintain pressure.

Time in operation: 60 minutes (10-12 PSI a bit slower than stovetop PC).

Total energy used: 0.20 kWh (200 watts)

First Place Tie

Fagor 4 Quart Electric Pressure Cooker

Stated Wattage: 800 watts

Actual Wattage Use: 750 watts to reach pressure, then cycled to maintain pressure.

Time in operation: 60 minutes (10-12 PSI a bit slower than stovetop PC).

Total energy used: 0.21 kWh (210 watts), virtually the same as the Mealthy unit.

Conclusions

Using a small electric cooking appliance is energy-saving. My experiment and the one conducted on the YouTube channel “Under the Median” suggest that, in some cases, a toaster oven can be as energy-efficient as a large slow cooker when cooking something that requires a longer cooking time. That was surprising.

The Instant Pot Dutch Oven uses a thermostat to regulate its slow cooking temperature. This makes it more efficient than the 6 Quart Manual CrockPot, which uses low power continuously.

There was also significant energy savings when comparing the large CrockPot with its 2.5-quart sibling. You don’t need a slow cooker of every size, but a smaller one will save a few energy pennies if you are a small family or a group of one.

The pressure cookers were outstanding in their energy efficiency. They require a lot of power to reach pressure (about 10 minutes at high power in my experiment), but then they barely sipped power, turning on the heat in 10-second bursts to maintain pressure. Naturally, you will see the most prominent energy savings when cooking something longer.  If you cook something under pressure for 1 minute, the cooker still will take 10 minutes at full power to build pressure before it starts the 1-minute countdown. 

Stovetop pressure cookers may or may not use more energy than electric ones, as my experiment couldn’t use a hob and had to rely on a lower-powered 120-volt induction burner.  Still, they are very efficient and generally cook faster than an electric pressure cooker. 

Different foods require different cooking methods. Slow cookers and pressure cookers cook with wet heat, while toaster ovens and regular ovens use dry heat. Use the most suitable process for the food you are cooking. You can improve the efficiency of a toaster oven or regular oven by using the recipe’s regular cooking temperature and the oven’s convection fan (if available). The fan can reduce cooking time by 25%, saving you money.  

Should you ever use your regular oven? Of course! Regular ovens regulate temperature better than most toaster ovens and have more capacity. Beyond Thanksgiving dinner, think about making several layers of a cake or trays of cookies at once. Additionally, think of cooking an entire meal in the oven. It takes no more energy to cook an entire meal in an oven vs. a single item. For some foods, you can turn off a regular oven up to 10 minutes before the food is done.  Regular ovens are well-insulated and will retain heat for a while after they are turned off. 

Ultimately, if you tailor the foods you make correctly with the most appropriate appliance, you will save the most energy. Where I live, a kWh costs $0.13, which isn’t too expensive, but pennies add up. In the UK, electricity is around 25 pence/kWh. In other countries, it is even more.  I saw one Reddit post where someone in an unnamed country said that energy prices are increased sixfold during peak usage times (4 -8 PM) as most people are making dinner then.  Wow!

Remember, cooking energy is 20% of your total energy bill.  Anything you can do to reduce it is worth your time.  I was so impressed with how energy-efficient pressure cookers are, I decided to do a deep dive into the topic.  Stay tuned.

Happy Eating!