Last week a record-setting heat wave afflicted much of the United States — yet there were no brownouts.

Electricity shortages during heat waves long have been common. We tend to miss what doesn’t happen, and what didn’t happen last week was electric power scarcity.

Two factors are at play, one positive and one vexing.

The positive factor is gradual decline in electricity demand. From 1996 to 2007, U.S. power consumption rose 23 percent. Since then, consumption has declined 16 percent. Taking population growth into account, per capita demand decline since 2007 is even greater. Details are in this fun report — every day must be a party at the Energy Information Administration.

The recession is not the root cause — electricity consumption began to moderate before the economy cooled. Homeowners, and businesses, finally are getting religious about high-efficiency lights, programmable thermostats and other power-saving technology. If the United States could achieve, in petroleum use, the same demand-curve moderation observed with electricity, America’s dependence on Persian Gulf dictatorships would decline, along with U.S. greenhouse gas output.

Now the vexing factor. When George W. Bush took office in 2001, he declared a looming electricity crisis that would require a national crash program to build generating stations and power lines. This political wolf-cry was forgotten when 9/11 happened. Forgotten, that is, by pundits and national candidates for office. But not by the permanent bureaucracy: last week the Federal Energy Regulatory Commission published rules, years in the making, intended to trigger a major initiative to build power lines.