Do Solar Panels Work During a Power Outage? (Usually Not — Here's Why)

It is the most common surprise in home solar. The grid goes down, the sun is blazing, your roof is covered in panels — and your house is just as dark as the neighbour’s.

The safety rule behind it

Grid-tied inverters are required to include anti-islanding protection. When the inverter stops seeing normal grid voltage and frequency, it disconnects within about two seconds and stays off until the grid comes back and holds steady for several minutes.

The reason is line workers. During an outage, crews treat distribution lines as de-energised. If thousands of rooftop inverters kept exporting into those lines, they would create energised “islands” on a circuit everyone believes is dead. So the standard is absolute: no grid, no output.

This is not a defect and not something an installer can switch off. It is the price of being connected to the grid at all — the same connection that lets you export surplus power for credit on every other day of the year.

Three ways to actually have power

1. Solar plus a battery (real backup)

A battery system adds a microgrid interconnect device that physically isolates your house from the grid during an outage. Inside that island, your inverter is free to run, your panels recharge the battery through the day, and the battery carries you overnight.

This is the only option that gives you genuinely seamless, multi-day backup. It is also the most expensive — see are solar batteries worth it for the cost and payback maths.

Most homeowners back up an essential-loads subpanel rather than the whole house: refrigerator, internet, lights, a few outlets, the furnace fan, maybe a well pump. That keeps the battery and inverter smaller and the bill far lower than whole-home backup.

2. A secure power supply outlet (daytime trickle)

Several string inverters include an SPS or “backup outlet” — a single receptacle that draws directly from the array during daylight. Expect roughly 1,000–1,500 watts, no automatic switchover, and nothing after sunset or under heavy cloud.

It costs very little to add at install time. It will keep a fridge cold and your phones charged. It will not run your house.

3. A generator

A standby generator ignores solar entirely and runs on natural gas, propane or diesel. It is cheaper per kilowatt of backup than a battery and unbothered by a week of rain. It is also noisy, needs fuel and servicing, and sits idle earning nothing for the 8,750 hours a year the grid is fine.

Which one is right for you

Your situation	Best fit
Rare, short outages	Do nothing, or add an SPS outlet
Frequent outages, medically critical loads	Battery on an essential-loads panel
Multi-day outages, storms, rural area	Generator, or a battery plus generator
Time-of-use rates or poor export credit	Battery — it pays for itself daily, backup is the bonus

That last row matters more than most people expect. In markets where exported solar earns far less than retail power, a battery is not only a backup device — it is what lets you use your own generation instead of selling it cheap. That is the case in California under NEM 3.0, and increasingly elsewhere.

What to ask your installer

• Does the quoted system include any backup capability at all? Ask directly — most quotes do not.
• If a battery is included, which circuits are backed up, and what happens to the rest?
• What is the continuous and surge output of the backup inverter? A well pump or an air conditioner has a startup surge several times its running draw.
• Can the system be battery-ready now and battery-added later, without replacing the inverter?

That last question is the cheap insurance. Specifying a hybrid inverter at install costs a few hundred dollars more and saves thousands if you add storage in five years.

Bottom line

Panels alone will not keep your lights on. If outage resilience is part of why you want solar, say so on day one — it changes the inverter you should buy, not just whether you bolt on a battery later.

Educational estimates only. Backup sizing depends on your loads, local code and utility rules. Confirm with a licensed installer.