Tesla Powerwall 3 Specs: What Tesla's Datasheet Actually Says

There is a lot of second-hand spec copy about the Powerwall 3 online, much of it carried over from the Powerwall 2 or rounded until it stops being true. Here is what Tesla's own documents say, and where the widely-repeated numbers go wrong.

Size, weight and where it can go

1105 x 609 x 193mm, 130kg. That is a two-person mount, and the wall has to carry it - a stud partition is not automatically suitable, which is something we check at survey rather than on the day. The enclosure is IP55 rated with IP67 protection where it is needed, so an outdoor wall is a normal installation rather than a compromise. In practice the deciding factors are a sound wall, sensible cable routes to your consumer unit, and somewhere that will not be built over later.

Capacity, and the real expansion ceiling

13.5kWh usable at installation. The figure people get wrong is what happens when you want more: the documented ceiling is four Powerwalls plus three Expansion units - seven boxes in total, 44kW and 94.5kWh. That is well past any domestic need, but it matters if you intend to add capacity in stages rather than all at once.

The two numbers most reviews get wrong

First, peak output. The 15.4kW figure is quoted at 240V. A UK supply is nominally 230V, so expect slightly less than the headline. Second, efficiency: Tesla does not publish a round-trip efficiency figure for the Powerwall 3 at all. What it publishes is 97.5% for solar going straight to the house and 89% for energy that goes through the battery first. Any review that gives you one round-trip percentage for this unit has filled in a blank that Tesla left, and you should treat the rest of its numbers with the same suspicion.

What it costs, hardware versus installed

Tesla lists the Powerwall 3 on its UK site at £5,000 without a Backup Gateway and £5,975 with one, excluding VAT, delivery and installation. That is a genuinely useful anchor, and worth stating plainly because a lot of UK solar writing claims Tesla doesn't publish a UK price. Our installed prices start at £7,450 retrofitted to existing solar and £12,920 with new panels, which covers the Gateway wiring, consumer-unit work, the DNO application, commissioning and the certification paperwork. Comparing a hardware price with an installed price makes the install disappear; compare like with like.

The warranty condition that outranks every spec

Tesla's European warranty document (Rev. 1.16, effective 3 December 2025) gives 10 years with 80% of the original 13.5kWh retained for the UK band - but only for a Powerwall bought from Tesla or a Tesla certified installer, and installation by anyone else is a listed ground for voiding it. “Unlimited cycles” is scoped to self-consumption, time-based control and backup, with other use capped at 37.8 MWh of throughput, and an internet connection is a condition of the full term. Read it before you sign anything, ours or anyone else's.

For the full picture including what it earns on a UK export tariff, read our Tesla Powerwall 3 review, or see what a battery-only retrofit involves on our page for home battery storage without solar.