Cooling during a power outage

In an outage the useful question is not what to run. It is what you already have, and how fast you are losing it.

A conditioned house holds a substantial amount of cool in its structure, its furnishings and its air. Everything below is about spending that slowly.

1. Close the blinds and curtains immediately, on every window the sun reaches. Solar gain is the largest heat input in most houses and it costs nothing to block — shading is the only cooling with no running cost.
2. Close the house up if it is hotter outside than in. Every door opened is a partial air exchange.
3. Retreat to one room, low down. A basement or ground floor room on the shaded side will hold its temperature far longer than the whole house will.
4. Stop opening the fridge and freezer. Partly to keep the food, partly because every opening dumps cold into the kitchen and pulls warm air in.
5. Turn off everything that makes heat. In an outage that is mostly automatic, but battery devices, gas appliances and candles all count.
6. Open up at night if outdoor air is cooler, then close again at dawn. This is the night purge done by hand.

None of that needs electricity, and together it matters more than any battery appliance you own.

A fan does not lower temperature. It makes a person feel several degrees cooler by speeding the evaporation of sweat — which in an outage is exactly the right trade, because it works on you rather than on a whole house you cannot afford to condition.

Note the trade running through that table: airflow and runtime are the same budget. 400 CFM for 16 hours, 850 CFM for 3, and the 2,300 CFM unit does not publish a figure at all.

The M18 makes it explicit — over 3 hours on high, 6.5 hours at 75% speed. Dropping one notch roughly doubles the time. In an outage, run everything slower than feels satisfying.

If you already own a cordless tool platform, buying the fan that matches it is by far the cheapest route into this, because the expensive part is the batteries and you have them. The battery fan category in full.

• Do not plan to run an air conditioner. A portable draws 1,300 W running and considerably more to start. A generator sized to the nameplate frequently cannot start a compressor at all.
• Do not freeze water for the ice trick. Setting aside that the freezer is off, a home freezer is a refrigeration cycle with both coils indoors — making ice heats the house. Ice you already have is fair game.
• Do not open the whole house during the day when it is hotter outside. It feels like doing something and it spends your remaining cool immediately.

1. A battery fan on a platform you already own. The batteries are the expensive part, and a fan that shares your drill packs is a small addition.
2. Charged packs. A 16-hour fan on a flat battery is a paperweight. Keep at least one charged in season.
3. Working CO alarms, especially if you own a generator. Test them.
4. Know your cooling center. Many areas open them during heat events, and for a long outage that is the right answer rather than a heroic effort at home.
5. Shading you can deploy fast. Blinds and curtains that actually close, on the windows that matter — the afternoon sun side first.
6. A plan for the people at risk in your household before the forecast, not during the outage.