A common surprise: the solar panels on a grid-tied roof do not power the home during an outage. Even with sun on the panels and the inverter running normally seconds before, the system stops. This is not a defect — it is a safety requirement, and it matters in BC, where winter storms and wildfire-season public-safety power shutoffs can interrupt supply.
Why grid-tied solar stops during an outage
Ordinary grid-tied inverters shut down automatically the moment they detect the grid is de-energised. This is called anti-islanding. The reason is safety: if power kept flowing from a solar system into a line that utility crews believe is dead, it can injure or kill the people working to restore it. Anti-islanding is not optional — it is a built-in, required behaviour.
What keeps the lights on
To have power during an outage you need a system designed for it: a battery and an inverter or transfer equipment that can disconnect from the grid and run selected loads safely on its own (islanding). That is a hybrid or a dedicated backup system, not a standard grid-tied system. The equipment, the wiring and the essential-load panel all have to be designed for the purpose.
Sizing essential loads honestly
A battery holds a finite amount of energy, and winter production is lower. The honest approach is to list the loads that must stay on — refrigeration, a furnace fan, lighting, a well pump, internet, medical equipment — and size the battery to those, for the outage duration you actually expect. Pretending a single battery can run an entire home is how customers end up disappointed in the first outage.
Questions to ask your installer
- Does this system provide backup during an outage, and is that in writing?
- Which loads stay on, and for roughly how long?
- What transfer or islanding equipment is included?
- Is the battery sized to my essential loads or to the whole building?