A home battery is worth it financially only when the gap between your cheapest and most expensive electricity is wide enough, and when you use a lot of power during those expensive hours. In most of Canada, flat electricity rates mean a battery won't pay for itself through bill savings alone; its value is mainly backup. Where steep time-of-use pricing exists, such as Ontario's ultra-low overnight plan, the math gets much more interesting. Here's how to run the numbers for your own home.
Key takeaways
- Savings come from the price spread: charge when power is cheap, discharge when it's expensive.
- Round-trip losses (roughly 10 to 15 percent) and only discharging on peak days shrink the theoretical savings.
- On flat-rate plans, a battery saves little or nothing on bills; backup is the main benefit.
- Even with a wide spread, simple payback on a typical $12,000 to $20,000 battery can be long, often well over a decade, unless incentives or extra revenue help.
- Put a dollar value on outage protection; for many households, that's what tips the decision.
The basic formula
Daily savings from time-shifting look like this:
Daily savings = (energy discharged × peak price) − (energy needed to recharge × off-peak price)
Energy needed to recharge is a bit more than what you discharge, because of round-trip efficiency:
Energy to recharge = energy discharged ÷ round-trip efficiency
Then multiply by the number of days per year you actually face peak pricing. Many time-of-use plans only charge peak rates on weekdays, so that's roughly 250 days a year rather than 365.
A worked example: Ontario's time-of-use plans
Ontario is the clearest Canadian case because households can choose between rate plans. The Ontario Energy Board sets these prices and updates them periodically; the figures below are the rates set for November 2025, used here for illustration. Check the OEB for current prices before running your own numbers.
| Ontario plan (Nov. 2025 rates) | Cheapest price | Most expensive price | Spread |
|---|---|---|---|
| Time-of-use (TOU) | 9.8¢/kWh off-peak | 20.3¢/kWh on-peak | 10.5¢ |
| Ultra-low overnight (ULO) | 3.9¢/kWh overnight | 39.1¢/kWh on-peak (weekdays 4–9 p.m.) | 35.2¢ |
Assume a battery discharges 10 kWh during the weekday peak and has 90 percent round-trip efficiency, so it needs about 11.1 kWh to recharge.
On the ULO plan: - Avoided cost: 10 kWh × $0.391 = $3.91 - Recharge cost: 11.1 kWh × $0.039 = $0.43 - Daily savings: about $3.48 - Annual (≈250 weekdays): roughly $870
On the standard TOU plan: - Avoided cost: 10 kWh × $0.203 = $2.03 - Recharge cost: 11.1 kWh × $0.098 = $1.09 - Daily savings: about $0.94 - Annual: roughly $235
These are pre-tax energy charges only. Delivery and regulatory charges, which don't change with timing in the same way, aren't affected, and bill credits or taxes will shift the final number slightly.
The honest caveat
The ULO numbers assume you'd actually use 10 kWh between 4 and 9 p.m. on weekdays. Many households use less in that window, especially with gas heat, so a battery may only displace 4 to 8 kWh a day. Also, the fair comparison isn't ULO-with-battery versus ULO-without; it's ULO-with-battery versus whichever plan suits you best without one. If you'd otherwise stay on standard TOU, your real benefit is the difference between your bills under those two scenarios.
Payback: rough ranges
Using approximate figures:
| Scenario | Annual savings (approx.) | Payback on $15,000 battery |
|---|---|---|
| Flat-rate province | $0–$100 | Doesn't pay back on savings alone |
| Moderate TOU spread | $150–$300 | 50+ years |
| Wide ULO-style spread, heavy evening use | $600–$900 | 17–25 years |
| Wide spread plus incentives or grid-program payments | Varies | Can drop meaningfully |
A battery warrantied for about 10 years that takes 17 or more years to pay back isn't a strong pure investment. That's why incentives, virtual power plant payments and backup value matter so much.
What about the rest of Canada?
Most Canadian households pay flat or tiered rates that don't vary by time of day. Some utilities offer or are piloting optional time-of-day rates, and these programs change, so check with your utility or our provincial guides. Without a time-based spread, a battery's bill-saving potential is small.
If you have solar, a battery may still help where exported electricity earns less than what you pay to import. Where net metering credits exports at roughly retail value, storing your own solar adds little financial benefit.
Putting a value on backup
Ask yourself what an outage costs you:
- A freezer full of food: several hundred dollars
- A flooded basement from a failed sump pump: potentially many thousands
- Lost work days for home-based workers
- Medical devices, pets, or comfort for vulnerable family members
If you'd otherwise buy a standby generator, that money offsets part of the battery's cost. See our generator vs. battery comparison.
Run your own numbers
- Pull a year of hourly or time-of-use data from your utility's online portal.
- Find your average weekday usage in the peak window.
- Plug it into the formula above with your current rates.
- Compare your best no-battery plan against your best with-battery plan.
- Subtract any available incentives from the installed cost; search by address with our rebate finder.
Frequently asked questions
Does a battery save money if I'm on a flat rate?
Very little, if anything. Without a price difference between times of day, there's nothing to arbitrage; the value is backup power and, if you have solar, possibly self-consumption.
Should I switch to an ultra-low overnight plan without a battery?
It can make sense if you can move big loads like EV charging, laundry and dishwashing overnight and use little power between 4 and 9 p.m. on weekdays. If your evening use is high and inflexible, the steep on-peak price can raise your bill.
Do battery savings decline over time?
Somewhat. Batteries lose capacity gradually, and rate structures change. Build in some degradation and avoid assuming today's prices will hold for 15 years.
The bottom line
A home battery pays its way through bill savings only where time-of-use spreads are wide and your evening usage is high, and even then payback is usually long. For most Canadians, the better question is whether reliable, quiet backup power is worth roughly the price of a used car to you. If it is, time-of-use savings are a welcome bonus rather than the whole case.
Sundamentals is an independent, non-profit education platform. Program details and prices change often — check current programs for your address in our rebate finder.