How Long a Home Solar Battery Lasts

It means how much energy the battery still holds, and for how long that is promised in writing. A battery slowly stores less than it did when new. That is why warranties make two separate promises. The first is that the unit will be free of defects for a set time. The second is that it will keep a stated share of its original capacity, measured in kilowatt-hours (kWh), the unit for stored energy.

A battery at 80% of its capacity still works. It runs your backup circuits for a shorter time and stores less of the day's solar for the evening.

Ten years against defects, and 80% of the rated capacity at ten years. Tesla's Powerwall warranty for Canada, effective 6 May 2026, covers the Powerwall 2, the Powerwall 3 and the Powerwall 3 Expansion. It says the Powerwall "will be free from defects for ten years following its initial installation date", and rates the unit at 13.5 kWh when installed.

For capacity, the warranty sets out two cases:

• Solar self-consumption or backup only. The battery keeps 80% of 13.5 kWh at ten years, with unlimited cycles.
• Any other use. The same 80% at ten years applies, but only up to 37.8 megawatt-hours of total energy through the battery.

Solar self-consumption means storing power from your own panels and using it in your home. A homeowner who uses the battery only with their own panels and for backup falls in the first case. On Tesla's figures, 80% of 13.5 kWh works out to 10.8 kWh, the least the warranty promises a Powerwall will hold at ten years.

A longer term with a lower floor. Enphase's warranty for the IQ Battery 5P covers the United States, Puerto Rico and Canada. It runs until the earlier of 15 years from the "Activation Date" or 6,000 discharged cycles. Until then, Enphase says the battery will keep the ability to store and discharge at least 60% of its nameplate capacity, provided it is installed and used in line with Enphase's install guide and data sheet. The warranty text counts cycles but does not define one, so ask the installer how the system reports them.

Enphase says this warranty applies to batteries activated on or after 1 December 2023, unless it posts a newer one, and tells owners to check its warranty page for the version that governs their unit.

The two products are not directly comparable. Tesla promises a shorter term, a higher floor and no cycle limit for solar and backup use. Enphase promises a longer term with a lower floor and a cycle cap. Which suits you depends on how hard the battery will work each day.

Off Grid Solar System Canada, a Canadian off-grid installer directory, lists a typical lifespan of 10 to 15 years for lithium iron phosphate (LFP) batteries, 3 to 7 years for AGM in daily use, 4 to 8 years for flooded lead acid that is maintained, and 4 to 7 years for gel. Those are planning figures from an off-grid cost guide, not a promise from anyone who would replace the battery.

Green Building Canada makes the same broad point without years. It says the most common battery types in solar are lithium ion and three kinds of lead acid: flooded, gel and absorbent glass mat (AGM). It says lithium-ion batteries cost more up front but last longer and need less maintenance. It names flow and sodium-ion batteries as emerging types.

The maker's warranty is the figure you can hold someone to, so ask which chemistry a quoted battery uses and ask for the warranty document with the quote.

Missed conditions. Both warranties have them.

Tesla says it needs to update a Powerwall's software over the internet to honour the full ten years. If the unit is offline for a long time or is not registered, Tesla says it may not be able to honour the full term, but it will always honour at least four years from installation. The warranty covers a Powerwall bought in Canada from Tesla or from an installer in Tesla's own programme, and installed in Canada.

Section 4 of Enphase's warranty makes coverage conditional on registering the product within 45 days of first installation, although the registration card printed at the end of the same document says failing to return the card does not reduce your warranty rights. Register within 45 days anyway, so the question never comes up. It says the battery should stay connected to the internet for the whole warranty period, so faults can be diagnosed remotely and firmware updated. The warranty clock starts on the "Activation Date". For a battery, that is the earlier of the "Energize by" date printed on the packaging, or the date the battery is activated and the owner has received "permission to operate" from the authorities. Enphase also covers only batteries sold by Enphase or one of its authorized resellers.

That gives you three tasks when the battery goes in:

1. Confirm the installer has registered the battery, and ask for proof.
2. Keep the battery connected to your home internet.
3. File the warranty document with your house papers, with the install date written on it.

Damage from causes outside normal use, and some of the cost of a fix. Tesla's Canadian warranty excludes defects or capacity loss caused by misuse, or by installation, operation, maintenance or repair that does not follow Tesla's specifications and manuals. It excludes accidents and events such as lightning, flood, earthquake and fire, repairs by anyone other than Tesla or an installer in its programme, and moving the unit to a new location without Tesla's written consent. It does not cover normal wear and tear, superficial marks, or noise that does not affect performance. Enphase's exclusions run along the same lines and add a battery not running the latest firmware Enphase has released, where that firmware could have avoided the fault.

Labour is where the two differ. Tesla says that when it repairs or replaces a Powerwall and the work is done by an installer in its programme, the warranty reimburses that installer's reasonable labour costs under Tesla's standard policies. Enphase says its warranty does not include the labour of removing the battery or installing the repaired or replacement unit. Ask your installer, in writing, who pays for that labour if a claim succeeds.

A repair does not restart the clock. Tesla says the remainder of the original warranty period applies to a repaired or replaced unit. Enphase says the same, or 90 days from when you receive the unit, whichever is later.

It can pass to the buyer, with conditions. Tesla says a later owner who provides proof of ownership can make warranty claims. Enphase covers a new owner only if the battery stays at its original location, the new owner submits a Change of Ownership Form, and the transfer fee is paid within 30 days of the transfer. Enphase says that form is required for coverage to continue. Put the warranty document and the registration proof in the papers you hand over at closing.

It runs your backup circuits for less time. BC Hydro, a British Columbia utility, lists battery size in kWh as one of the factors that decide how long a battery's backup lasts. A Powerwall at Tesla's ten-year floor holds 10.8 kWh rather than 13.5, so size the battery with that loss in mind. The site's guide to sizing a home battery for GTA outages walks through the circuit list and the arithmetic.

In this index, 16 of the 161 solar companies list battery storage. The index does not check the battery warranty any of them offers, so the questions above go to the installer, and the maker's warranty document should come with the quote. For price per kWh and what sits inside a battery quote, see the guide to comparing home battery quotes and the battery storage cost guide.