Go easy on the A/C this afternoon *update*

Texas’ main electric grid operator is warning customers to reduce their usage during the peak power demand hours of 3 p.m. to 7 p.m. today as high temperatures and unexpected power plant outages will stretch supplies.

“We are expecting the statewide power supplies to be very tight over peak hours today, primarily due to the forecast for continued temperature extremes which causes higher than normal electricity use, and because of unexpected unit outages,” said Kent Saathoff, vice president of grid operations and system planning for the Electric Reliability Council of Texas (ERCOT).

Despite headlines from some other news outlets, ERCOT is not saying “brownouts” are likely or rolling blackouts. Rather this is the sort of warning given as the first of ERCOT’s three-stage emergency steps (see it below).

Consumers are asked to shut off unnecessary lights and electrical appliances between 3 p.m. and 7 p.m., delaying laundry and other activities electricity-consuming until later in this evening.

According to ERCOT up to 3,800 megawatts of power plant capacity is offline today due to unplanned maintenance issues.

ERCOT isn’t allowed to disclose which units are down, but according to the Nuclear Regulatory Commission’s web site one of the two 1,200 megawatt units of the Comanche Peak nuclear power plant southwest of Fort Worth is offline for an unplanned maintenance issue.

Also about 500 megawatts from some Houston-area power plants were offline unexpectedly today, according to sources.

One megawatt is roughly enough electricity to power 500 average homes under normal conditions in Texas, according to ERCOT, or about 200 homes during hot weather. That means the downed plants could handle about 760,000 typical Texas homes.


As of 11:30 a.m. power demand is expected to peak at 65,550 megawatts. That’s below the all-time peak demand record of 65,776 MW, which occurred Aug. 23, 2010, but more than what was expected to be the peak for this summer, 63,898 MW.

By 2:25 the peak projection was down to 63,789 MW

That’s a mark that was actually topped on Wednesday, when ERCOT set a new July record with 64,203 MW. (To be fair, ERCOT projects the summer demand peaks based on “normalized weather” data, using a widely accepted methodology that is detailed in this report .)

Other conservation tips from the Public Utility Commission’s “Powerful Advice” include:

  • Turn off all unnecessary lights, appliances, and electronic equipment.
  • When at home, close blinds and drapes that get direct sun, set air conditioning thermostats to 78 degrees or higher, and use fans to cool your house.
  • When away from home, set air conditioning thermostats to 85 degrees and turn all fans off before you leave. Block the sun by closing blinds or drapes on windows that will get direct sun.
  • Do not use your dishwasher, laundry equipment, hair dryers, coffee makers, or other home appliances during the peak hours of 3 to 7 p.m.
  • Avoid opening refrigerators or freezers more than necessary.
  • Use microwaves for cooking instead of an electric range or oven.
  • Set your pool pump to run in the early morning or evening instead of the afternoon.

The conservation warning is the first of a three-step plan ERCOT can use to handle power demands should the situation deteriorate.

Under Energy Emergency Alert Level 1, ERCOT can bring in power from other neighboring grids — if available — via a handful of DC lines.

If the situation does not improve, ERCOT can move to a Power Warning, or Energy Emergency Alert Level 2, which lets it call on large commercial/industrial customers to cut off predetermined amounts of demand.

The third level, a Power Emergency, or Energy Emergency Alert Level 3, allows ERCOT to have local power utilities (such as CenterPoint Energy in the Houston area, CPS Energy in San Antonio) reduce demand through rolling blackouts, which typically last 15 to 45 minutes in each area.