Guide · Batteries
Tesla Powerwall 3: reviewed by a Tesla certified installer.
By the ECONEXIS team, Tesla certified installers · Updated October 2026
Short answer
Yes, it's a strong choice — the biggest single battery we fit: 13.5 kWh with its own solar inverter built in, fitted from £6,390.
It suits homes that want one tidy unit doing everything, and we size it to your usage at the free survey.
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MCS-certified installer · Cert. no. NAP/79987/26/1
What it is: a battery and a solar inverter in one box
Four numbers tell you most of what you need to know.
- 13.5 kWh
- usable storage — the biggest single battery we fit
- 11.04 kW
- power output — runs most of a home at once
- 97.5%
- solar to home, through its built-in inverter
- 10 years
- Tesla warranty, 80% guaranteed at year 10
The Powerwall 3 is a home battery with its own solar inverter built in. An inverter is the box that turns your panels' power into power your home can use.
Because it is built in, your panels connect straight to the Powerwall. You get one box on the wall instead of two.
What does 13.5 kWh mean for you? One kWh is one unit on your electricity bill. So a full Powerwall 3 is enough for a typical family's evening and night.
Tesla's app shows your solar, battery and house use as it happens. You also use it to set when the battery charges.
| What | Tesla Powerwall 3 |
|---|---|
| Usable capacity | 13.5 kWh |
| Power output | Up to 11.04 kW (UK, single phase) |
| Built-in solar inverter | Up to 20 kW of panels, 3 inputs |
| Efficiency | 97.5% solar to home · 89% through the battery |
| Expanding | Up to 7 units in total (94.5 kWh) |
| Where it goes | Indoors or outdoors · wall or floor · IP67 |
| Size and weight | 1105 × 609 × 193 mm · 130 kg |
| Warranty | 10 years · 80% guaranteed at year 10 |
Figures from Tesla's UK Powerwall 3 datasheet (2026) and Tesla's UK warranty.
Why do people choose it?
There are four good reasons to pick it.
One unit does the lot
A new solar and battery system needs fewer boxes. If you already have solar, it can take over from your old inverter at the same time.
It can run the whole house
It has the power for far more than the lights and the fridge. It can even start heavy loads, such as a heat pump or an electric shower. That matters most in a power cut.
Tesla's software
Of the brands we fit, Tesla's app is the most polished. And the warranty puts no limit on charges for normal home use.
It grows with you
You can add extra batteries later — Tesla calls them Expansion packs, 13.5 kWh each — or more Powerwalls, up to seven units in all.
How much does a Powerwall 3 cost to fit?
You pay for a battery and a solar inverter in one price. That is why it costs more up front than a battery on its own.
Will it keep my lights on in a power cut?
Yes — with Tesla's Backup Gateway 2. Tesla requires the gateway for backup.
When the grid goes down, the gateway separates your home from the grid. The battery then takes over and keeps your home running.
The gateway is its own line on your quote, so you can see exactly what backup adds. (How power-cut backup works)
Already have solar panels?
That's fine. A Powerwall 3 can join a system another firm fitted. Its built-in inverter can take over from your old one at the same time.
Things to know before you choose it
Four things are worth knowing before the survey.
Where will it go?
It weighs 130 kg, so we plan where it goes at the survey. It can hang on a wall or stand on the floor.
Can it go outside?
Yes. Its battery and electronics are sealed against dust and water (rated IP67), and it works from -20°C to 50°C.
Does it need the internet?
Tesla asks for a steady connection to keep the full 10-year warranty. It's also how the app works.
What does backup need?
Power-cut backup needs the Backup Gateway 2 above, shown as its own line on your quote.
How does it compare with other batteries?
We fit Fox ESS and Sigenergy too, so we'll tell you honestly which suits your home. The Powerwall 3 vs Sigenergy vs Fox ESS guide puts all three side by side.
Who fits it?
We do. ECONEXIS is a Tesla Powerwall certified installer and MCS certified.
We design your system and fit it in a day. Before we leave, we set up the Tesla app with you.
The bottom line
The Powerwall 3 is the all-in-one choice. You get the biggest single battery we fit, its own solar inverter, whole-house power and Tesla's app. A 10-year warranty that guarantees 80% at year 10 backs it.
If you want one tidy unit doing everything, it's hard to beat. We'll tell you at the free survey if another battery suits your home better.
Powerwall 3 questions
How much does a Tesla Powerwall 3 cost to install in the UK?
We fit one Powerwall 3 — 13.5 kWh with its built-in inverter — from £6,390. An extra battery (Tesla Expansion pack) added to a Powerwall 3 you already have is from £4,990. All fitted, 0% VAT, fixed after a free survey.
How much is an extra Powerwall 3 battery (Expansion pack)?
An extra battery — Tesla's Powerwall 3 Expansion pack, 13.5 kWh — added to a Powerwall 3 you already have is from £4,990 fitted, 0% VAT. It plugs into your Powerwall 3, and up to three can be added.
Is a Tesla Powerwall 3 worth it in the UK?
Yes, for homes that want the biggest single battery we fit, enough power to run the whole house, a solar inverter built in and Tesla's app — with the warranty set at 80% after 10 years and no limit on charges for home use. We size it to your usage at the free survey.
What are the downsides of the Powerwall 3?
It costs more up front than a battery alone, because the solar inverter is built in. It weighs 130 kg, so we plan where it goes at the survey. It needs a steady internet connection to keep the full 10-year warranty, and power-cut backup comes with Tesla's Backup Gateway 2.
Does the Powerwall 3 work in a power cut?
Yes, with Tesla's Backup Gateway 2, which Tesla requires for backup. When the grid goes down, the gateway separates your home and the Powerwall keeps it running. The gateway is its own line on your quote.
Can a Powerwall 3 go outside?
Yes. It is rated for indoor and outdoor use, its battery and electronics are sealed to IP67, and it works from -20°C to 50°C. It mounts on a wall or stands on the floor.
How many Powerwall 3 units can I have?
Up to four Powerwall 3 units, plus up to three expansion units — seven units and 94.5 kWh in total. Expansion units stand on the floor behind a Powerwall 3.
What warranty does the Powerwall 3 have?
10 years. In the UK, Tesla guarantees it still holds at least 80% of its 13.5 kWh at year 10, with no limit on charges for solar, cheap-tariff and backup use. It needs to stay connected to the internet for the full term.
Why is the Powerwall 3 more expensive than other batteries?
Because it is a battery and a 20 kW solar inverter in one unit, with up to 11.04 kW of output — enough to start heavy loads like a heat pump or an electric shower.
Where we install
Everything in this guide is fitted by our own team across Essex, Herts, Beds, Bucks and Kent — a company owner on every install.
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Thinking about a Powerwall 3?
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