Optimum Power Outage Duration to Minimize Cold Load Pickup

Hi Tim - Depending on who manufactures your power producing equipment, you may want to contact their Applications Engineering department, or seek out their web site. I know from experience that the group over at GE Energy in Schenectady, NY handles grid questions like yours (for "extreme" cold environments like Canada and Russia) for their stuff (Gas Turbines, Generators). Much luck. - Larry

Hi, Tim. Welcome to CR4!

We went through this exercise 10 years ago, in preparation for Y2k. There's really no rule of thumb for determining duration. In my area most heat is from natural gas, so our peak is from cooling load in the summer, but the concept is the same. I recommend you speak to the local emergency management agency. They may have information on how quickly a typical home loses heat.

Unfortunately, there's a lot of guesswork & assumption involved, because every house will have different insulation propoerties, thermostat dead band, heating types, heating unit efficiencies, etc. Still, you can get a starting point by using an "average" home.

Fortunately, we were able to do some experimentation. Using the homes of volunteer employees, we ran a series of tests where we timed the dead band (time from shutdown of the air conditioner until it came back on) on the installed thermostat. We also bought several popular models of replacement t-stats and tested them as well. We set our starting point at the median dead band time (1/2 of the t-stats had hit their limits & were calling for cooliing, while the other half were still off).

Fortunately, Y2k was a bust, and we didn't need to use our load-shedding plan at the time. We did use it last summer, after a substation fire. We found that older neighborhoods tended to have higher cold load pickup after the off cycle, while those built after about 1975 had lower than expected load pickup. I suspect that most older homes have less insulation, and therefore more thermal transfer.

When you create your load shedding plan, leave some flexibility to adjust the cycle time based on actual experience and current weather conditions. Then pray you never need to use it, and realize that, no matter what you decide, someone will second-guess you after the fact and say you did it wrong.

Thanks for the insight, your answer is along the lines of what I was thinking. Good observation about the dwelling age and your testing program. Thank you very much.