Tesla Powerwall 3 Installers in Cornwall

The Powerwall 3 is Tesla's third-generation home battery, launched in the UK in November 2024. It is a wall-mounted lithium iron phosphate (LFP) system with 13.5 kWh of usable energy, an integrated 11.04 kW solar inverter with three MPPT inputs, and 11.5 kW of continuous AC output (24.4 kW peak for 10 seconds). It is rated IP67 for outdoor installation and operates from -20°C to +50°C — which covers every weather extreme Cornwall has ever recorded.

The major design shift compared with Powerwall 2 is that the Powerwall 3 is DC-coupled with its own solar inverter built in. That means in a new-build solar + battery installation you don't need a separate string inverter — solar panels connect directly into the Powerwall. This saves around £1,500 in equipment, eliminates an entire failure point, and improves round-trip efficiency to 89% (Powerwall 2 was 90% AC-coupled but the system loss with a separate inverter was higher overall).

For retrofit jobs (adding a Powerwall 3 to an existing solar system) the unit operates AC-coupled and the existing solar inverter stays in place. Either way the Backup Gateway 2 is required for whole-home backup, grid-isolation and Tesla Energy Plan eligibility.

Quick-look engineering data, taken from Tesla's UK datasheet (April 2026 revision):

• Usable capacity: 13.5 kWh
• Continuous power: 11.5 kW
• Peak power: 24.4 kW (10 seconds, motor start)
• Round-trip efficiency: 89% (97.5% solar to battery)
• Chemistry: Lithium iron phosphate (LFP)
• Integrated solar inverter: 11.04 kW, 3 MPPTs, up to 20 kW PV input
• Dimensions: 1,105 × 609 × 193 mm (43.5 × 24.0 × 7.6 in)
• Weight: 130 kg
• Mounting: Wall or floor (with floor stand kit)
• Ambient operating range: -20°C to +50°C
• Ingress protection: IP67
• Noise output: < 50 dB(A) at 1 m
• Warranty: 10 years, 70% capacity retention, unlimited cycles
• Connectivity: Wi-Fi, Ethernet, cellular backup (UK 4G)

The continuous 11.5 kW output is the headline feature. By comparison, the Powerwall 2 delivered 5 kW continuous, and most competing batteries top out at 5–7 kW. The Powerwall 3 will run a 7 kW EV charger, a 4 kW immersion and a 3 kW induction hob simultaneously without grid support.

Both units remain available in the UK as of May 2026. The choice depends on your starting point:

• Retrofit to existing solar — either works. Powerwall 2 (13.5 kWh, 5 kW continuous) is around £1,200 cheaper installed. Powerwall 3 (13.5 kWh, 11.5 kW continuous) is faster, supports backup of heavier loads, and is the newer platform.
• New-build solar + battery — Powerwall 3 almost always wins. The integrated solar inverter saves the cost of a separate inverter and simplifies the install.
• Heat pump + EV household — Powerwall 3, because heat pumps draw 3–7 kW and EV chargers draw 7 kW. Powerwall 2's 5 kW continuous can't cover both at once without grid support.
• Multiple-battery installations — both stack to 4 units. Powerwall 3 stacks deliver 46 kW continuous; Powerwall 2 stacks deliver 20 kW continuous.

If you'd like to compare alternative brands at similar price points, see our FoxStar EP5 and battery storage Cornwall overview.

Tesla controls the wholesale price tightly, so installed prices in Cornwall are tightly clustered around £9,500–£11,500 depending on cable runs, mounting position (wall vs floor stand), and whether the Backup Gateway 2 is included. All prices below include 0% VAT (until March 2027), MCS certification, DNO G99 notification, app onboarding and 10-year warranty registration:

• Powerwall 3 — retrofit to existing solar (no PV work): from £9,500 fitted.
• Powerwall 3 — battery only, no existing solar: from £10,200 fitted (includes Backup Gateway 2).
• Powerwall 3 + 5 kWp new solar PV: from £15,400 fitted.
• Powerwall 3 + 6 kWp new solar PV: from £16,800 fitted.
• Powerwall 3 + 8 kWp new solar PV: from £18,200 fitted.
• Powerwall 3 expansion battery (2nd or 3rd unit added later): from £6,800 fitted.

For a complete combined solar + battery breakdown see our solar panel costs page and finance options for 0% APR or low-rate spread payments.

The Tesla Energy Plan is a UK electricity tariff available exclusively to Powerwall owners (any generation). As of May 2026 it offers:

• 15p/kWh flat import — significantly under the Ofgem Q1 2026 cap of 24.67p/kWh.
• 15p/kWh export — Tesla buys all surplus solar from your Powerwall at the same flat rate.
• £10/month standing charge equivalent (paid via your usage).
• No peak rate penalty, no shoulder rate — every kWh in or out at 15p.

Compared with Octopus Cosy (12p off-peak, 38p peak, 22p shoulder), Tesla Energy Plan wins for households with unpredictable peak-time demand or with significant evening loads that the battery can't always cover. Cosy wins for households that can fully charge overnight and avoid peak draw.

We onboard you onto the Tesla Energy Plan during commissioning if you elect it, and the changeover (from your current supplier) typically takes 21 days. Eligibility requires: Powerwall installed, Backup Gateway 2 in place, smart meter SMETS2, no economy 7 setup, supply MPAN in England, Wales or Scotland (Cornwall qualifies).

Cornwall has the highest concentration of weather-related power cuts in mainland Britain — Storm Eunice (February 2022) left parts of west Cornwall without power for over 72 hours, and Storm Babet (October 2023) caused multi-day cuts in Bodmin Moor and Roseland. Whole-home backup with the Powerwall 3 + Backup Gateway 2 is genuinely useful here, not just a luxury feature.

How it works:

• The Backup Gateway 2 sits between your meter and your consumer unit. It senses grid loss within 100 ms and islands your home onto the Powerwall.
• Your lights, fridge, freezer, broadband, central heating pumps, alarm and Wi-Fi keep running with no interruption.
• If you have solar PV, the Powerwall continues to charge during the day even when the grid is down — extending backup indefinitely in summer.
• Configurable load shedding lets you keep heavy loads (oven, EV charger, immersion) off during backup to preserve runtime for essentials.

For a typical 4-bed Cornish family home, a fully charged Powerwall 3 delivers about 24–36 hours of essentials-only backup, or 36–60 hours with daytime solar top-up. Multiple Powerwalls extend this proportionally.

A typical CCS Powerwall 3 installation in Cornwall takes one full day (8–9 hours) on site:

1. 0800–0900: Arrive, dust sheets down, mark battery position, drill mounting holes (or position floor stand). Battery is 130 kg so two engineers handle it onto the mount.
2. 0900–1100: Run AC cable from battery to consumer unit (typically <15 m). Install Backup Gateway 2 between meter and CU. Add 32A or 40A protective device.
3. 1100–1300: For new-build solar: install isolators on roof, run DC string cabling to battery, terminate at MPPT inputs.
4. 1300–1500: Power down, switch consumer unit tails through Backup Gateway 2, test islanding (we deliberately drop the supply to verify backup engages). Power back on.
5. 1500–1700: Commission via Tesla installer app, pair your phone to the homeowner Tesla app, configure operating mode (Self-Powered, Time-Based Control, or Backup-Only), and demonstrate the system.

You receive your MCS certificate, building control notification (electrical Part P) and 10-year warranty registration within 5 working days. SEG or Tesla Energy Plan onboarding follows within 21 days.

The Tesla app is the gold standard of the home-battery industry. From your phone you can:

• See live import/export, battery state of charge, solar generation and home consumption.
• Switch between Self-Powered, Time-Based Control and Backup-Only modes.
• Configure a reserve percentage (e.g. always keep 20% for power-cut backup).
• View historical generation, consumption, savings and CO₂ avoided.
• Receive over-the-air firmware updates (typical: 2–3 per year).
• Pair with the Tesla EV charging system for joint solar-priority charging if you also drive a Tesla.

All Powerwall 3 units include cellular fallback (Tesla-provisioned 4G SIM) so connectivity continues even during home Wi-Fi outages. We provide a 30-minute app walkthrough at handover and a follow-up call 30 days post-install to check optimisation.

The Tesla Powerwall 3 warranty is 10 years from the date of installation with the following terms:

• 70% capacity retention guaranteed at year 10 (i.e. at least 9.45 kWh of the original 13.5 kWh).
• Unlimited cycles — Tesla does not cap the warranty by cycle count.
• Coverage includes the battery, internal solar inverter, gateway and all internal electronics.
• Labour for warranty repairs is included for the first 5 years; year 6–10 covers parts only (CCS holds spare Powerwall 3 inventory in Cornwall for fast in-warranty swap).
• Transferable with the property if you sell.

Tesla projects a 20-year usable life with normal cycling. For most Cornish homeowners that's two decades of generation + storage. As your installer of record we provide first-line support — call us first, not Tesla — and we escalate warranty cases on your behalf.