Concern over global warming had led to a steady stream of advice on how you can cut your “carbon footprint”. Eating vegetables instead of an average serving of chicken or pork, for example, is claimed to save on the order of half a kilogram of carbon dioxide equivalent emissions. The environmentalists I have come into contact with in Oxford go so far as to recommend reducing energy consumption by taking cold showers: heating the water for a 25-gallon shower with an inefficient heater can require up to five kilowatt-hours, for 2.5 to 5 kg of CO2-equivalent. I’ve seen lengthy lists of recommendations. Most with no numbers for actual savings attached, and most including items that either save nothing at all or actually increase consumption—“drive instead of fly!” is a particularly egregious example of confusing inconvenience with energy savings.

On all these lists, I’ve never seen anything about conventional versus microwave ovens, so I looked up some numbers. Electric ovens and ranges usually draw around two kilowatts each at peak, and about half this over the course of lengthy use (the elements aren’t being driven at maximum the whole time). Microwaves are usually rated at around 700–900 watts, but let’s generously assume they’re grossly inefficient and draw around 1500 watts. If you have the option of heating something up in the microwave for five minutes or bringing an electric oven up to temperature and then warming it in that for twenty minutes, the microwave saves you 80% of the energy used—about 250 to 500 grams of CO2 equivalent. Warming a meal with a microwave instead of an oven reduces emissions by almost as much as cutting meat out of that meal entirely.

Environmentalist silence on this issue is not difficult to understand when you realize that popular environmentalism is as much about a dislike for technology as it is about protecting the environment. Of course, it’s also about self-righteous condescension, and vegetarians tend to like to cook…