Cooking with Gas vs. Pressure – which uses more energy?

In my previous blog post I hypothesized that multi-cookers, such as Instant Pots, were the most efficient method of cooking available for a home. In this article, I will run through one experiment that supports that hypothesis.

I cooked 1 cup of white rice in my multi-cooker, a Zavor LUX LCD 8-QT, and measured the electricity consumption over the entire process using a kill-a-watt meter. I then cooked the same amount of rice on our gas stove and timed each step of the process to estimate the natural gas consumption.

Multi-cooker – 113 Wh

I followed the manual for cooking long grained white rice, which says to add 1.5 cups water and cook on high pressure for 10 minutes. The instant pot took a few minutes to come up to temperature and pressure. I measured the peak wattage which was 1,257W. Since the Zavor LUX LCD 8-qt is rated at 1,300W that measurement makes sense. During most of the 10 minutes of pressure cooking, the instant pot measured only 1W because the cooking vessel is well insulated and did not lose much heat or pressure during the process. Through other measurements, I know LCD display consumes about 1W. The process of cooking the rice took 113 Wh (watt-hr) with the Instant Pot.

Gas range – 978.5 BTUs

I followed my tried and true recipe for cooking rice on the stove: add 2 cups of water for every cup of rice, bring to a boil and then simmer for 15 minutes covered.

The 1 cup of rice and 2 cups of water took 4 minutes 41 seconds to come to a boil. I turned it down to a simmer for 15 minutes with the lid on the pot. The key to cooking rice on the stove is to not check on the rice in while it is cooking. When 15 minutes is done, if I have time, I turn off the gas and let it sit another 5 minutes just to be sure. I did not run the exhaust vent fan like I should, which would have made the energy consumed overall even higher for the gas range.

Estimating BTUs

My stove is a simple old Kenmore range/oven and the 4 burners are all rated at 9,500 BTUs/hr. At full power bringing the rice and water to a boil, I consumed 741 BTUs of natural gas. For simmering, I am going to estimate that it is using 10% of full power, so 950 BTUs/hr. I’ve found simmer settings for various fancy ranges to be in that range. Simmering the rice used another 237.5 BTUs. Combining the two steps together, cooking rice on a gas range consumed 978.5 BTUs.

0.078 hr * 9500 BTUs/hr + 0.25 hr * 950 BTUs/hr = 741 BTUs + 237.5 BTUs = 978.5 BTUs

Comparison – Instant Pot vs Gas Stovetop for 1 cup rice

To convert from BTUs to Wh we divide by 3.41214.

Because we get all of our electricity from solar and renewable energy, we do not suffer the generation loss of converting from fossil fuel to electricity at the power plant. Our multi-cooker uses 40% of the energy to cook rice as using the gas range. Even if we got most of our electricity from modern combined cycle natural gas power plants like most of New England, the multi-cooker is still over 38% more efficient than the gas cooktop.

The next time you are trying to decide whether to cook something on the stove or in your multi-cooker, consider that the multi-cooker is significantly more efficient and will not produce harmful combustion gasses in your home. Another bonus is that it is usually faster too.

Happy Greening!
Jon

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