I hope to make this post short and efficient, so let’s get right to the point: I’m skeptical of the recent decision by New York State to ban new (2026 or later) residential hookups of natural gas for the sake of climate change. After a brief look-see of my own, I am left to wonder whether any engineers were called to testify about the net environmental effect of home heating and cooking. New York State’s new law feels like a political statement to me, not a scientific one.
I’ll start with what I learned in my tedious college thermodynamics class, namely that the efficiency of generating electricity via steam turbine maxes out at 40%. (Meaning, if you put 100 units of energy into the process, you only get 40 units of electrical energy out.) Newer combined-cycle turbines are 60% efficient but they are less common.
Overall — and this is my main point — as of today, electricity generation in the U.S. from all sources, coal, gas, uranium, wind, solar, hydro and others, is still barely 40% efficient. “In 2019, U.S. utility-scale generation facilities consumed 38 quadrillion BTUs (quads) of energy to provide 14 quads of electricity.” [Italics mine.]
Compare this to the efficiency of natural-gas home heating — 80% (older models) to 95% (newer ones). Even in old systems, homeowners get more heat per BTU when they burn natural gas in their own furnaces vs. buying utility-generated electric heat. This means that the typical home natural gas furnace currently creates less, not more, greenhouse gas than if the same heating load were provided by electricity.
This will remain true until all of our traditional fossil-fuel electricity-generating plants are shut down — and specifically, until half of U.S. electricity is generated by zero-emission renewables with the other half generated by combined-cycle natural gas steam turbines.
Currently, only 40% of our electricity is generated by non-fossil-fuel sources and only 35% is generated by combined-cycle natural gas. So clearly, we have a ways to go until banning natural gas hookups in residences makes sense from a greenhouse gas standpoint.
But what about safety? There has been a spate of alarmist articles about the dangers of natural gas cooking appliances, some focused on the harmful effects of nitrogen dioxide byproducts and others on the risks of carbon monoxide poisoning. Certain studies showed associations between gas appliances in the home and asthma symptoms in women, but it is not clear to me that other socio-economic factors (for example, are gas appliances more likely to be found in more polluted cities?) are not in play.
With respect to carbon monoxide (CO): About 9 deaths in the U.S. a year are attributable to CO leaks from defective natural gas furnaces; 3 from natural gas cooking; and 2 from natural gas water heaters. For comparison, 90-plus deaths a year are caused by the CO from gasoline-powered generators and engines, but that issue does not seem to energize many interest groups.
In any case, my take is that the political powers-that-be in New York State needed to score some friend-of-the-environment points, and so they got ahead of the game — even though their new law may, perversely, cause a near-term increase in greenhouse gas emissions. But who, other than an ex-New-Yorker engineer, would bother to point that out?