FindSolar.caHere is the fact that surprises more new solar owners than any other: when the grid goes down on a sunny afternoon, an ordinary grid-tied solar system goes down with it. The panels are fine, the sun is free, and your house is still dark. This is by design, and knowing why before you buy lets you decide whether backup is worth paying for, instead of discovering the gap during your first outage.
Why panels shut off in a blackout
Grid-tied inverters are required to disconnect the moment they lose the grid, a safety behaviour called anti-islanding. The reason is the crew up the pole: a line worker repairing what they believe is a dead wire cannot be met by your rooftop quietly energizing it. Every certified inverter in Canada does this automatically, and no installer can or should disable it.
What backup actually requires
Backup power needs equipment that can disconnect your house from the grid and run it as an island: a battery with a hybrid or backup-capable inverter, plus a transfer arrangement and usually a critical-loads panel listing the circuits that stay on. With that hardware, the fridge, furnace fan, well pump, internet and lights ride through an outage, and the panels recharge the battery when the sun is up. Without it, solar is a bill-reduction machine, excellent at that job and silent in a blackout.
Whole house or essentials?
Whole-home backup exists, but it is an engineering exercise: big loads like electric heat, ranges and air conditioners drain batteries quickly and demand high surge capacity. Most homeowners get better value from an essentials design, sized around what an outage actually threatens. A fridge, freezer, some lights and the internet draw little; it is the motors and heaters that decide the design, which is why battery sizing starts from your critical loads, not from a product brochure.
Deciding whether backup is worth it to you
Count your outages. In most Canadian cities they are rare and short, and a battery bought purely for backup is expensive insurance, which is a legitimate purchase as long as you price it as insurance rather than as an investment. Where outages are frequent or long, or a sump pump or medical equipment raises the stakes, backup earns its keep in a different currency than payback. Our cost calculator includes battery planning ranges so you can see the premium before anyone quotes it.
Questions homeowners ask
If the sun is shining, why do my solar panels shut off during a blackout?
Because your inverter is required to disconnect when the grid fails, a safety rule called anti-islanding. It protects the line crews repairing the outage from being met by power flowing backward out of your roof. Every certified grid-tied inverter in Canada behaves this way automatically.
Do I need a battery to use solar during a power outage?
For practical purposes, yes. Backup requires a battery with a backup-capable inverter and a transfer arrangement that islands your house from the grid. A rare inverter feature can offer a small daytime-only outlet without a battery, but it will not run your home. Ordinary grid-tied systems provide no backup at all.
Can solar keep my whole house running during an outage?
With enough battery and inverter capacity, yes, but whole-home backup is expensive because heaters, ranges and air conditioners drain storage fast. Most homes are better served by a critical-loads design that keeps the fridge, heat circulation, water, internet and lights on and lets the big loads wait.
How long will a home battery keep my house running?
Divide the battery's usable kWh by what your protected circuits actually draw. A 10 kWh battery running a 500-watt essentials load lasts roughly 20 hours, and less in real life with cycling losses; the same battery on a 3 kW load lasts about three. Sunny days stretch it, because panels recharge the battery mid-outage.
Can I add a battery later if I install solar now?
Yes. AC-coupled batteries retrofit onto almost any existing system, or you can install a hybrid inverter now so a battery drops in later. Saying so during design costs little and avoids paying twice for inverters. Tell the designer battery-later is on the table and get the compatibility in writing.
Will my solar system automatically restart when grid power comes back?
Yes. After the grid returns, the inverter waits a mandated few minutes of stable power, then reconnects and resumes on its own. No ladder, no switches. If monitoring shows the system still offline well after an outage ends, that is a service call, not a homeowner repair.