The Gas Stove Wars Are Not About Gas Stoves

I just returned from a whirlwind trip to New Zealand and Australia. I visited my family in New Zealand and in Australia I presented new research on agriculture's nitrogen legacy at Monash University and the University of Sydney.

While visiting my parents, I once again got to benefit from the wonders of an induction stove top. This NY Times article describes how much better these stoves are than alternative technologies.

"Using the power of electromagnetism, these cooktops can boil water in nearly half the time of a gas or conventional-electric burner yet also hold such low temperatures that it’s almost impossible to scorch a sauce or burn melted chocolate. They’re also safer than other types of cooktops, with no open flame and little residual heat after you’ve turned them off." NY Times, 6/25/19

They're easy to clean, too. This Grist article explains how they work:

The secret to an induction stove is that it’s basically just a big magnet. And when a pan is sitting on the stovetop, that magnetic field creates little electric currents that swirl through the pan. This heats up the pan, but leaves everything around it cool. It also means that induction stoves can heat up food in a fraction of the time for a fraction of the energy.

Stove top technology has become a hot political topic in the United States this year. In January, Bloomberg News published a story in which a commissioner on the U.S. Consumer Product Safety Commission suggested that the agency may consider a ban on gas stoves due to their effects on indoor air quality and their contribution to climate change. Opponents of the Biden Administration responded with indignation.

More American homes actually have electric cooktops than natural gas. However, most of these are electric coil rather than induction technology. Less than 1% of American homes have induction stovetops.

There are two reasons why policymakers might target gas stoves. First, the flames emit nitrogen oxides (NOx), an air pollutant that irritates human airways and can cause respiratory symptoms that put people in the hospital. Long-term NOx exposure can contribute to the development of asthma. There are debates about whether NOx from gas stoves has a meaningful effect on human health and whether they are worse for human health than other modes of cooking.

I'm persuaded by Emily Oster's conclusions that (i) "gas stoves are not particularly healthy for lungs, especially small ones," and (ii) "the evidence suggesting this factor is responsible for a sizable share of asthma in kids is probably overstated." But, I still operate the hood fan when I cook with my gas stove.

The second reason for policymakers to target gas stoves is to mitigate climate change. Greenhouse gas emissions from houses make up about 6% of total emissions in the United States. Almost all these residential emissions are from combustion of fossil fuels (emissions from electricity generation are counted separately in this inventory).

About 90% of fossil fuel burned in American homes is natural gas or propane; the remainder is fuel oil for heating. Three quarters of natural gas is used for space heating or water heating. Together, these two sources emit almost 200 million metric tons (MMT) of CO2 annually, compared to 1,800 MMT from transportation and 1,600 MMT from electricity generation. Cooking with natural gas produces 6 MMT of CO2 annually, or about 0.1% of total US emissions.

Gas stoves use a relatively small amount of energy, so they are a small contributor to climate change. However, all emissions can be broken into small pieces that make little difference globally. Driving my gasoline-powered car three miles to work rather than biking will have a negligible climate effect. The key to effective climate mitigation is to figure out the climate cost of a particular activity and then whether there are cleaner options at lower cost.

The latest estimate of the cost to society of emitting a ton of CO2 is $185. The average house that cooks with natural gas emits 150kg of CO2 per year from cooking, which is the equivalent of driving 379 miles in a typical passenger car (22 miles per gallon). These emissions impose estimated climate costs of $28 dollars per year.

Induction stoves cost about $600 more to buy than gas stoves, and they may be $20 more or less expensive to operate per year depending on where you live. The climate benefit of an induction stove depends on whether it uses electricity generated from low-carbon sources such as solar or wind paired with battery storage, rather than fossil fuels. Even in the best case scenario of low-carbon electricity, it is difficult to justify spending an extra $600 on an expensive induction stove to get $28 per year of climate benefits.

However, this is not about stoves. Space and water heating use most of the natural gas. Consumers can save money and benefit the climate by switching to heat pumps for space heating and electric water heaters (assuming low-carbon electricity). Solar pool heaters work well. Once people go electric for space and water heating, it isn't going to be worth maintaining all the natural gas infrastructure to deliver a tiny amount of gas to homes just for cooktops.

Cities and states are banning natural gas hookups in new buildings. These policies may be premature, but it’s important to understand two things: (i) in the future, it will not be economic to run gas pipes to every home because new homes will use low-carbon electricity for space and water heating, and (ii) induction stoves work so much better than gas, but they are expensive; a less expensive option is a coil electric glass cooktop.

I made the bar charts using this R code.

In case you want to see it, here are annual emissions in equivalent miles in a typical passenger car (22 miles per gallon).