The panel that knows the well pump matters more than the pool heater.

Deciding what stays on

A house has more loads than any backup source can carry at once. Something has to choose.

Every residential microgrid runs into the same arithmetic. The sum of everything in a large house, air conditioning, electric cooking, the well pump, the pool equipment, two EV chargers, the dryer, the wine room, is far more than a generator or a battery can carry at one time, and far more than the house ever actually draws at one time. Backup equipment is sized to the real coincident load, not the nameplate sum, and that only works if something prevents the rare moment when everything starts together. For decades that something was a critical-loads subpanel: a short list of circuits moved to a separate panel that is the only thing the backup feeds. It works, it is simple, and it means the rest of the house is dark no matter how much spare capacity the generator has.

A smart panel changes the arrangement from a fixed list to a set of rules. Each breaker in the panel is controllable and metered, so the system can see that the generator is at its limit and shed the pool heater, or see that the battery has an hour left and pause the EV charger, or see that the sun is up and the roof is producing and let the air conditioning run. The owner sets priorities once, from a phone: the well pump and the gate are never shed, the kitchen is second, the chargers are last. During a shutoff the panel enforces those priorities every second without anyone in the house thinking about it. The whole house stays connected to backup, and the sources are never overloaded.

Load management is also what lets equipment be sized honestly. Without it, a generator has to be sized for the worst coincidence of loads, which usually means a liquid-cooled unit on a house that would be fine on an air-cooled one if the chargers paused for an hour. With it, County Line can size the generator and the battery to the loads that genuinely run together and let the panel handle the exceptions. The same logic applies to the EV charger on its own: a charger that can be told to slow down or pause when the house is on backup is a charger that will never trip the generator at two in the morning.

The electrical work is the panel itself and the design around it. A smart panel replaces or supplements the main panel, which on an existing house means a service shutdown, a permit and an inspection, and on new construction means specifying it before the rough-in. The transfer device, the battery inverter, the solar inverter and the EV gateway all have to be placed correctly relative to it so that the panel actually controls what it thinks it controls. That one-line diagram is the heart of the residential microgrid, and it is the drawing County Line produces before any equipment is ordered.

Smart panels are not required for a residential microgrid, and the honest page in this series covers the house where a plain critical-loads subpanel is the better answer. For a large property with many high-draw circuits and a family who wants the whole house on backup without buying the largest generator made, the smart panel is usually where the design lands.

Back to the overview: Residential Microgrid.