16. With What Shall We Cook Then?

 With What Shall We Cook Then?

Gas or electric cooking--which makes more sense, energy-wise?  What about those weirdly fast induction stoves--do the Europeans know something we don’t? These are questions that might haunt the obsessive cook who hasn’t found the time to research them.

Cooking uses energy to generate the heat needed to induce chemical reactions that get the food cooked.  How you get that energy into the food is the question here.

In the U.S., cooking uses less than 1% of our total energy footprint and maybe 3-5% of our household energy.  Still, if one is trying to reduce one’s overall energy usage and carbon footprint, every energy use makes a contribution, right?  

Two types of electric stoves - standard coil burners and induction ranges - operate quite differently. Induction ranges heat up crazy-fast, and cool down almost instantly. An induction stove produces an oscillating magnetic field that directly heats the pan you are cooking with. When there is no pan on the burner it uses almost no energy, but when the pan is put on the burner the electromagnetic field  produces electric currents in the metal of the pan itself, thus heating it virtually instantly. 

The induction burner itself never gets very hot; the pan also responds much more quickly to changes in settings and is easier to fine tune. This is a lot like a gas cooktop, which most chefs prefer because of the quick response, but induction burners are about as quick as gas.  

Electric coil burners, on the other hand, are often frustratingly slow to heat up and cool down. In these stoves, the electric current heats the burner coil and that heat is then transferred to the pan, while some is lost to the surrounding air. You might think this would have a big impact on “efficiency.” 

It turns out, though, that induction burners are only slightly more energy efficient than a standard electric burner.  According to the U.S. Department of Energy, the induction burners are rated at 84% efficiency when used with the right cookware. Regular electric burners are rated at 75% or so, reflecting how much of the energy actually heats the pan and how much is lost to the surroundings--so, not much difference.

An additional consideration is that induction burners require specific cookware. They will work with your traditional cast iron and other magnetic pans, but not  with aluminum or non-magnetic stainless steel (bye-bye, good ole Paul Revere Ware!).

And how do electric and gas ranges compare in terms of efficiency?  If you use gas, you may have noticed that a fair amount of the heat goes out from under the pot and into heating the room instead of the food.  In fact, because of this, the efficiency of gas cooking is around 30-40%, quite a bit lower than either electric option.  It is also more likely to remove stray wrist hair, which can be good or bad --

As to the carbon footprint of the different cooktops:  Electricity generation produces an amount of CO2 that depends on the source.  In heavy coal burning regions, one kilowatt-hour (kWh) of electricity generates a little over 2 lbs of CO2. Here in Maine it depends on your provider.  If you have the “standard offer” through CMP (a mixture of sources that varies day-to-day) one kWh these days generates about 0.8 lbs of CO2.  If you have all renewable electricity, of course, you generate virtually no CO2.

Gas generates its CO2 right in your kitchen where it’s burned (yes, it still goes into the atmosphere).  Additional CO2 is generated in the process of extracting and transporting the gas.  Burning  gas produces about 0.5 lbs of CO2 to produce one kWh worth of heat, but since it’s only half as efficient as the electric burner, it effectively produces about 1 lb of CO2 to get that much heat to the food. Then, considering the CO2 involved in its extraction and transportation, it ends up at a bit over 1 lb. 

The amount of CO2 you generate also depends on how much you use the burners and whether you use them effectively. Typical stove-top electric burners set to “high” use between 1200 and 2500 watts.  That translates to 1.2 to 2.5 kWh for every hour of use. Typical gas burners range in peak output from 1500 to 3500 watts (or 5000 to 12,000 Btu per hour.) This is a bit more than the electric because less of the heat gets to the food.

So, to summarize, gas is 50% less efficient than the electric options, and produces 20 to 30% more CO2 based on the current “standard offer” electricity.

In the end, though, what sort of cooktop you have is not the most important element of your carbon footprint, and you can probably realize far greater cooking-related energy savings by just cooking less.  (“I KNEW it - now they’re gonna make us eat raw food!”)  Still, for some people, conscientious appliance choices are gratifying...  

And, if we can ever have cocktail parties again, “cook-top carbon footprints” is just the type of conversation starter we’re always looking for, right?  We’ll bring the raw vegetables and dip! Wait, what? We aren’t invited??

Paul Stancioff, PhD., is a professor of Physics at the University of Maine Farmington who studies energy economics on the side.  He can be reached at pauls@maine.edu.  Cynthia Stancioff is an amateur naturalist who likes to write.