Sheet E-105 / Circuit 5
Batteries and generators.
Wind season in the hills means a few long outages a year. Backup ranges from a $1,400 interlock kit for the generator you already own to an $18,000 battery that switches over before the clocks blink. Most homes need something in between.
What a house actually needs in an outage.
Not everything. Ask yourself what you miss in the first hour without power. For most families it is the fridge, a few lights, the internet and the garage door. Add a well pump or a medical device if you have one.
That list is about 2 to 4 kilowatts, which a modest battery or a portable generator covers. Backing up central AC and an EV charger is a different, bigger job. We size to the list, not the showroom.
- 1
Fridge and freezer
About 150 watts running, more on start.
- 2
Lights and outlets
LED lighting on a few circuits barely registers.
- 3
Wi-Fi and phones
Small load, big difference to your day.
- 4
Furnace fan or well pump
Worth a circuit in the hills.
Interlock, transfer switch or battery.
Installed prices, permit included, equipment where noted.
| Option | How it works | Switch over | Installed |
|---|---|---|---|
| Interlock kit and inlet | A plate on your panel that lets a portable generator feed it safely. You pick circuits by flipping breakers. | Manual, a few minutes | $1,400 to $2,400 |
| Transfer switch | A separate switch that moves chosen circuits to a standby or portable generator. Generator not included. | Manual or automatic | $3,500 to $7,500 |
| Home battery | Wall mounted storage that takes over the moment the grid drops. Pairs with solar if you have it. | Automatic, seconds or less | $12,000 to $18,000 |
Battery prices include the unit, the gateway and the install. Ask us what your utility currently offers; programs change and we check at the quote.
Permits and paperwork.
Every option on this page needs an electrical permit, and a battery also needs the utility's sign off before it can run in parallel with the grid. We file both. Never backfeed a generator through a dryer outlet with a homemade cord. It can kill a lineworker down the street, and that is not a scare tactic. It is why interlocks exist.
Full panel and no room for a transfer switch? Start with a panel upgrade. Want the car to charge off the same system? See EV charger installs. Or ask us to size it.