Home battery storage

Batteries do two separate jobs and the case for each is different. One is backup, keeping essential circuits alive when the grid goes down. The other is arbitrage: storing cheap or self-generated electricity and using it when electricity is expensive. In Ottawa the first is easier to justify than the second.

Step one: decide which job you are buying. For backup, what matters is power output in kilowatts, how many circuits you want to carry and whether you need whole-home or essential-loads-only. For load shifting, what matters is capacity in kilowatt hours and the spread between the price you charge at and the price you avoid. Sizing for one and hoping for the other produces an expensive compromise.

Step two: the electrical design. Backup requires a transfer arrangement and usually a separate critical-loads panel, so that when the grid drops the battery serves only what you chose rather than trying to carry the whole house including the air conditioner. This is where most of the labour and a good deal of the cost sits. Whole-home backup needs considerably more battery power and often a service upgrade.

Step three: siting. Lithium iron phosphate batteries are the current residential norm and they want a location that stays within their operating temperature range. In Ottawa that argues for an interior basement or a heated garage rather than an unheated one or an exterior wall, because capacity falls and charging is restricted at low temperatures. A battery in an unheated Ottawa garage in February is a battery you cannot fully use on the coldest days, which are exactly the days the grid is most stressed.

Step four: the electrical work and authorization. As with the array itself, the electrical work must be reported to the Electrical Safety Authority through a notification filed before work begins, and if you hire someone it must be a Licensed Electrical Contractor (Electrical Safety Authority, Notifications and inspections). A battery that can export to the grid is a distributed energy resource in its own right as far as your distributor is concerned, so the connection arrangement needs to cover it.

How long it takes. A battery added to an existing array is typically one to three days of installation once the equipment is on site, plus the ESA inspection. Installed with a new array it adds little to the calendar. Equipment lead times have been the real variable in recent years, so ask what is actually in stock.

What it costs in Ottawa in 2026. Indicative. A single residential battery of roughly 10 to 13 kilowatt hours, installed with the transfer arrangement and a critical-loads panel, commonly runs $15,000 to $25,000. Two units for larger backup, $25,000 to $40,000. What moves the number: whether a critical-loads panel already exists, the distance from the panel to the battery location, whether the service needs upgrading, and whether any structural or fire-separation work is needed at the mounting location.

The Ontario rebate, and its condition. The Home Renovation Savings programme offers up to $5,000 for battery energy storage at $300 per kilowatt hour and up to 50 per cent of total costs, alongside up to $5,000 for solar panels at $1,000 per kilowatt and the same 50 per cent cap (Home Renovation Savings, solar and battery storage). Note the condition carefully, because it applies to the battery as much as the panels: these incentives are provided for projects designed for load displacement only, and participants who receive them are not eligible to participate in a net metering agreement with their distributor. The participant agreement requires repayment of the full rebate within 30 days if you enter a net metering agreement at any time in connection with the measures installed (Home Renovation Savings, Solar and Storage Participant Agreement).

Whether it pays. Be honest with yourself about this. Under the Regulated Price Plan effective 1 November 2025, the ultra-low overnight plan prices overnight electricity at 3.9 cents per kilowatt hour and on-peak at 39.1, while standard time-of-use runs 9.8 off-peak to 20.3 on-peak (Ontario Energy Board, Electricity rates). A battery charging overnight on the ultra-low plan and discharging on-peak has a genuine spread to work with, and that is the strongest arbitrage case available in Ontario. Even so, a 10 kilowatt hour battery cycled daily on a 35 cent spread saves roughly $3.50 a day before round-trip losses, which is under $1,300 a year against $15,000 or more of equipment. The backup value is real and is not measured in cents per kilowatt hour. Buy it for that, and treat the bill saving as a secondary benefit rather than the business case.

What makes Ottawa different. Two things, pulling opposite ways. Ottawa has had genuinely disruptive outages, including multi-day losses after severe summer wind events and the 1998 ice storm, and outage risk in winter here is a health question rather than an inconvenience, because a furnace without power is a house without heat. That is a real argument for backup. On the other side, cold reduces usable battery capacity, so the location must be heated, and Ontario's rebate route rules out net metering, which changes how the whole system should be sized.

What to ask before you buy. Backup or load shifting, and which have you designed for. How many kilowatts of output and how many kilowatt hours of capacity, and which circuits will it actually carry. Where is it going, and is that location heated. Is a critical-loads panel included. What is the round-trip efficiency and the warranted cycle count. Does the warranty cover capacity degradation and to what percentage. Am I taking the rebate, and do I understand that it forecloses net metering. Show me the bill saving arithmetic with my own consumption data.