Decide which problem you are solving
For one household, the priority is keeping a few selected circuits available. For another, it is making more use of solar generation at a different time. The design conversation should distinguish those aims.
Do not assume that a system selected for one objective automatically performs every other function. Ask for its normal operation and outage operation to be explained separately.
Separate stored energy from available power
A kilowatt-hour is a unit of energy; a kilowatt is a unit of power. A useful specification needs both, along with the manufacturer’s operating limits.
For a purely conceptual calculation, 10 kWh of available energy divided by a constant 1 kW load equals 10 hours. That arithmetic excludes reserve, conversion losses, changing loads and equipment limits; it is not a product specification or a backup-duration promise.
- Which loads operate at the same time?
- Are any loads difficult to start?
- What energy reserve is held back?
- What happens when the reserve is reached?
Ask what is included in backup
A backup plan should identify the supported circuits and the equipment needed for the intended operation. Ask how the system responds when grid power is lost and restored.
If solar is expected to support the system during an outage, confirm that capability for the complete proposed design. Panels on a roof are not, by themselves, proof of backup capability.
Review the home around the battery
The proposed location, temperatures, clearances, access and electrical work matter. These requirements are equipment- and site-specific, so ask for the actual installation arrangement rather than a generic product photograph.
For an existing solar installation, have compatibility assessed before treating storage as a simple add-on.
Compare value in more than one column
Keep the purchase price, installation work, operating assumptions and any expected financial benefit visible. Resilience can be a valid priority without presenting an uncertain payback as guaranteed.
Read the specific warranty, capacity-retention conditions and support terms. A warranty duration alone does not explain what is covered or who pays for related work.
Questions, answered.
Is the numerical example a suggested system size?
No. It is an intentionally simplified arithmetic example to distinguish energy from power. A real design requires load data, equipment specifications and a site assessment.
Should essential medical equipment rely on this guide?
No. Discuss dedicated continuity requirements with the equipment provider and qualified professionals. This general guide does not establish an emergency-power solution.
Further reading
For primary guidance, see Natural Resources Canada: solar energy and Ontario Energy Board: net metering. Ontario-specific rules do not apply across every province. Confirm the current requirements with your utility.