Free tool · Updated October 2026

Home Battery Sizing Calculator

Enter your daily kWh usage, how many hours of backup you want, and your province. The tool returns a recommended usable-kWh capacity, specific Canadian battery product options at that capacity, and a payback estimate against your province's rate structure. No sign-up required.

Daily electricity usage (kWh)

kWh/day

Divide your annual kWh (on your utility bill) by 365. The Canadian median is about 23 kWh/day for a 3-bed home with gas heat; 35-45 kWh/day for homes with heat pump + EV.

What's the battery for?

Backup hours to cover

hours

Essential loads only during outage (fridge, furnace fan, lights, WiFi — recommended)

Province

Ontario: Class B TOU — strong arbitrage. 2.5¢ off-peak / 15.1¢ on-peak.

How the sizing math works

Battery sizing in Canada depends on four inputs: daily kWh usage, desired backup hours (or TOU arbitrage window), depth of discharge (DoD) tolerated by the battery chemistry, and inverter round-trip efficiency. Our calculator chains these together: usable kWh = (daily kWh × backup_hours ÷ 24) ÷ (DoD × η), where η is the round-trip efficiency (typically 0.89 for Powerwall 3, 0.95 for LFP chemistries).

For arbitrage-driven sizing (TOU customers in Ontario and Alberta), we skip the backup-hours input and instead model the daily peak-period consumption shift — typically 10-14 kWh for a Canadian home on Class B TOU. Pure arbitrage sizing lands at one Powerwall 3 or equivalent for most homes.

We publish usable kWh throughout, not nameplate. Nameplate numbers are misleading when comparing LFP (95% DoD) vs NMC (85-90% DoD) batteries — a "15 kWh" LFP delivers more usable energy than a "15 kWh" NMC. Where a battery product has an integrated inverter (Powerwall 3, Sonnen ecoLinx) we subtract the inverter's rated continuous loss; where it's external we assume a 97% inverter efficiency on top.

Payback estimates use current provincial retail rates: Ontario Class B TOU (2.5¢ off-peak / 15.1¢ on-peak, ~12.6¢/kWh arbitrage), Alberta Solar Club (summer daytime export 25-30¢/kWh), BC Hydro Step 2 (13.2¢/kWh retail), Quebec Rate D (6.8¢/kWh flat), Nova Scotia Power (~18¢/kWh retail). Rate data refreshed quarterly against utility rate filings.

Frequently asked questions

How does this battery sizing calculator work?

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You enter your daily kWh usage (from your utility bill), the number of backup hours you want to cover during an outage, and your province. The tool calculates the usable kWh capacity you need after accounting for depth-of-discharge limits (typically 85-95% for lithium batteries) and inverter efficiency, then suggests specific battery products at that capacity along with a payback estimate for your province's rate structure.

What size battery do I need for my home in Canada?

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A typical Canadian home uses 20-30 kWh/day. For 24 hours of essential-load backup (fridge, furnace fan, lights, WiFi — not full home load), 10-13 kWh of usable battery capacity is enough. One Tesla Powerwall 3 at 13.5 kWh usable covers this. Homes with heat pumps or EVs often benefit from 20-27 kWh (two batteries). Full-home off-grid or multi-day backup requires 30+ kWh.

What's depth-of-discharge (DoD) and why does it matter?

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DoD is the percentage of a battery's rated capacity you can safely use without hurting its lifespan. Lithium-iron-phosphate (LFP, like Franklin aPower) can discharge to ~95% DoD. Lithium-nickel (NMC, like Tesla Powerwall) is typically ~85-90%. So a 'nameplate' 15 kWh LFP battery delivers ~14.3 kWh usable; a 'nameplate' 15 kWh NMC battery delivers ~13 kWh. Our calculator uses usable kWh throughout to avoid this confusion.

Does the calculator account for solar?

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Yes — tick the 'I have (or plan to install) solar' option. The calculator shifts from pure backup sizing to self-consumption + TOU arbitrage sizing, which usually results in a smaller recommended capacity because solar refills the battery during the day. For most Canadian homes with a 7-10 kW solar array, a single Powerwall 3 is enough.

Does the Clean Technology ITC apply to a home battery in Canada?

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No — residential owner-occupied homes don't qualify. The 30% refundable Clean Technology ITC applies only to batteries used in a business context (farm, commercial, incorporated). For a residential home battery in Canada in 2026, the main incentive paths are BC Hydro's residential battery adder (up to $2,000 paired with their solar rebate) and municipal PACE programs where available (Toronto HELP, Alberta CEIP).

Is this calculator accurate enough to size a real purchase?

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The output is 85-90% of the way there — good enough to budget and compare quotes. The remaining 10-15% requires an installer site visit to confirm your electrical panel can accept the backfeed (CEC Rule 84-024 / the 20% rule), inverter compatibility with any existing solar, and specific load profile. Use the quote CTA at the bottom to get three verified installer quotes based on your sizing output.