Solar and Power Outages: What Your System Will and Won't Do When the Grid Goes Down
One of the most common solar misunderstandings is that panels on your roof will keep the house running when the grid fails. In most cases they will not. Whether your system helps during an outage depends entirely on how it was designed.
Why standard grid-tied solar shuts down
Grid-tied inverters are designed to stop exporting power when the utility goes down. This anti-islanding protection prevents power from flowing into lines that crews believe to be dead. It is a safety requirement, not a flaw, but it means a basic grid-tied system gives you no power in a blackout even on a sunny day.
What does keep the lights on
| Setup | Works in an outage? | Notes |
|---|---|---|
| Grid-tied, no battery | No | Shuts down with the grid |
| Hybrid with battery and backup output | Yes, for the circuits it is wired to supply | Needs an inverter and wiring designed for backup operation |
| Off-grid system | Not affected | No grid connection to lose |
| Portable solar generator or small battery system | Yes, for small loads you plug in | Limited by battery capacity and output |
| Standby generator | Yes | Needs fuel and safe installation |
If outage protection matters to you, tell the designer up front. Backup capability is a design requirement, not an add-on you can assume.
Decide what really needs power
Backup systems usually supply a limited set of essential circuits rather than the whole building. Common choices include the refrigerator, lighting, communications, a furnace blower or circulation pump, and a sump pump. Large electric loads such as electric heating, ranges and dryers are normally too big to back up on a modest battery.
How long will the battery last?
A rough estimate is:
Runtime (hours) = usable battery energy (kWh) ÷ average load (kW)
As an illustration, 8 kWh of usable energy supplying an average load of 1 kW would last about 8 hours, before losses and without any solar recharging. In winter, solar recharging may be modest, so do not count on the sun to refill the battery during a storm. Our guide to reading battery specs explains the usable capacity numbers.
Winter outages
Winter storms are when many Canadians want backup power most, and also when solar and batteries have the hardest job. Output is lower, snow may cover the array, and cold limits what lithium batteries can do. See our guides on solar panels in winter and lithium batteries in the cold for the details. Many owners pair batteries with a generator for long events.
Safety basics
- Never connect a generator to your building wiring without a properly installed transfer switch. Backfeeding can injure utility workers and damage equipment.
- Never run a generator indoors or in an attached garage. Carbon monoxide is deadly.
- Have any backup wiring done by a licensed electrician, with the required permit and inspection.
Questions to ask before buying a backup-capable system
- Does the inverter have a backup or off-grid output, and which circuits will it supply?
- How is the changeover done, and how quickly?
- What surge power can it deliver to start motors?
- How will the battery behave at the temperatures where it is installed?
- Are the inverter and battery certified for use in Canada?
Where to look
Hybrid options in our catalogue include the Jinko hybrid solar system kit with battery and inverter and the Sunpal 5kW–10kW hybrid system with a Deye inverter. Ask whether the specific model supports backup output and how it must be wired for that purpose. You can compare the full range in the complete solar systems collection.
This article is general information, not electrical or engineering advice. Backup wiring must be done to code by a qualified, licensed professional.