Design the house for the shutoff, not the storm.

The outage is the brief

Start with the outage you will actually have.

A Public Safety Power Shutoff is not a storm knocking down a line. It is Southern California Edison or LADWP de-energizing a circuit on purpose because the wind, the humidity and the fuel on the ground make their own equipment a fire risk. The utility announces it a day or two ahead, turns the lines off as the wind rises, and turns them back on only after crews have patrolled every mile on foot or by air. Edison tells customers in high fire risk areas to plan for an outage that may last several days, and a wind event on a Monday can keep a canyon dark into Thursday. That is the design brief for a residential microgrid in this part of California: not minutes of backup, but days, in the hottest and driest weeks of the year, with the fire itself as the reason the power is off.

The loads that have to stay on.

The first design question is therefore not which equipment but which loads. County Line starts every residential microgrid with a list: what in this house has to stay on through a multi-day shutoff, and what merely would be nice. On a hillside property the list is longer than people expect. A well or booster pump, because without it there is no water and no fire hose. The gate and the garage door, because the shutoff may precede an evacuation. Refrigeration and freezers. The network, the cameras and the phones, because cell towers lose their own backup after a day. Medical equipment. Air conditioning for whoever is home in a heat wave. EV charging, if the car is how the family leaves. Everything else, the pool heater, the dryer, the wine room compressor, goes on the second list and gets power when there is power to spare.

How long each power source carries the house.

Time is the second design question: how long each power source can carry the house. A battery covers the first seconds and the first hours silently, and that is what most people picture when they think of backup. It does not cover the third day. A standby generator on natural gas runs as long as the main is pressurized, which in a shutoff it is; on propane it runs as long as the tank is sized for. Solar recharges the battery each day of the shutoff if the inverter is set up to run while islanded, which most solar installations are not. The design decides which source covers which hour, so the generator rests at night on the battery, the battery refills from the roof in the morning, and the house never notices the handoffs.

The third question is order and automation. When the utility drops, the transfer switch or the gateway has to open the connection to the grid within a fraction of a second, the battery has to take the load instantly, the generator has to start within seconds, the smart panel has to shed the loads on the second list, and the solar inverter has to be told it is allowed to keep producing. All of that is settings, wiring and sequencing, and it is the reason a residential microgrid is an electrical design rather than a shopping list. County Line writes that sequence down, wires it, and then tests it by pulling the main with the owner watching.

The honest limit: no design keeps a house running through a fire. A residential microgrid keeps the water pumping, the gate opening and the information flowing during the shutoff that precedes a fire, and it keeps a family comfortable through the shutoffs that never become one. The evacuation plan is still the evacuation plan.

Back to the overview: Residential Microgrid.