Electric power supply-demand is nuanced

This post over at Marginal Revolution is a great example of why industry-specific knowledge is important, and why extrapolating from general economic principles can be dangerous.

Can you discuss whether [energy efficiency via smarter thermostats] can possibly work? As I understand the power industry, such a high percentage of the costs are upfront (with nuclear plants in particular, but with carbon burning plants as well) and the marginal price of producing energy (up to plant capacity) is so low, that falling demand would mostly cause plants to cut prices until they were again operating at capacity.

So “saving” energy at the consumer level won’t really reduce total energy consumption or gas emission.

As people familiar with the electric power industry already know, baseload power (e.g. nuclear) has low marginal cost but is also not supplying marginal supply - that role is played in most regions by gas turbines (and in some places by older coal or oil), which sell pretty much at marginal cost. A quick way to check this is by multiplying the price of natural gas by the heat rate of the marginal gas plant, and comparing that to the price per MWh of electricity - they will usually be pretty close.

The best commenters do a good job of explaining this. Ignore the first half dozen or so, Alfred and valuethinker are strong.

For what it's worth, U.S. industrial and commercial load is still below 2007 levels; energy efficiency standards from EPAct and EISA may be one factor, although obviously very difficult to parse out the effect of energy efficiency from other drivers like, say, the economy.