What happens during a PSPS shutoff, and how a home battery gets you through it

A Public Safety Power Shutoff (PSPS) is a deliberate outage. When forecasts call for strong, dry winds across fire-prone country, PG&E, Southern California Edison and SDG&E de-energize lines so that a falling branch or a failed conductor cannot start a fire. The utility usually gives one to two days' notice, and the power stays off until the wind drops and crews have inspected the lines.

What it feels like at home

• Shutoffs often start in the afternoon or evening and run overnight, sometimes for two or three days in a long wind event.
• The whole neighborhood is dark. Cell towers may run on backup for a while and then fade.
• Refrigerators hold temperature for a few hours; freezers for a day if they stay closed.
• Well pumps, garage doors, medical equipment, internet and home security panels all stop unless they have their own power.
• Restoration is in stages. Being "in the footprint" does not tell you when you will be back on.

Solar alone does not help

A grid-tied solar system shuts down during an outage. Inverters are required to stop exporting when the grid goes away, so the panels sit idle in the sun. To use your own solar power in a shutoff you need a battery and a transfer switch that can island the house from the grid.

How a battery carries the house

A home battery with backup capability detects the loss of grid power, disconnects the house from the utility in a fraction of a second, and keeps powering the circuits it is wired to. If you have solar, the panels recharge the battery during the day, which is what lets a system run through a multi-day shutoff rather than a single night.

The Tesla Powerwall 3 we design around stores 13.5 kWh of usable energy and can deliver 11.5 kW continuously. Expansion units add capacity without adding another inverter.

Sizing: what do you actually need to keep on?

This is the whole question, and it is why our battery designer asks it first.

• Essentials. Refrigerator, lights, internet, phone charging, a well or sump pump. One Powerwall often covers a night, and with solar can run for days.
• Most of the house. Add the kitchen, a mini-split or furnace fan, the garage door. This is usually one or two units depending on your evening load.
• Whole home. Central air conditioning, electric ranges and EV charging are the big draws. Two or more units, and some loads may still be managed during the outage.

The designer models an hour-by-hour typical California day and a grid outage against your bill, then suggests the Powerwall count that covers the load you chose. Everything it shows is an estimate before incentives, and the final design is confirmed by a licensed installer after a site visit.

Two things a battery does not do

It does not replace evacuation. If your area is under a fire order, a battery keeps the lights on while you pack, not while you stay. And it does not change the utility's decision to shut off; it only changes what that decision means for your household.

If you want to see what keeping your home running through a shutoff would take, start the battery designer. If you are also thinking about solar, the solar designer sizes panels and battery together. Both end with a Revio advisor if you want to talk it through.