What to expect from a Tesla Powerwall 3 installation in a UK home

Helpful video reference. We use Alps Electrical Ltd's UK installation video "Our First Tesla Powerwall 3 Installation | Solar & Battery Project | Alps Electrical Ltd" as the video reference here. Alps Electrical are a multi-award-winning family electrical firm based in the North East, and this video from December 2024 shows exactly what a first Powerwall 3 job involves, including the wiring sequence and commissioning steps that matter.

1. Understand what is different about the Powerwall 3

The Powerwall 2 was an AC-coupled system. Your solar panels connected to a separate solar inverter, which converted the DC generation to AC. The Powerwall 2 then had its own internal inverter to charge from and discharge to that AC circuit. Two inverters, two sets of losses.

The Powerwall 3 is DC-coupled. It contains a built-in 5 kW solar inverter, so the DC from your panels connects directly to the Powerwall 3. There is only one inverter stage, which improves round-trip efficiency and simplifies the overall system design. One unit on the wall handles solar conversion, battery charge and discharge, and grid interaction.

The implication for existing solar owners is important: if you have a Powerwall 2 and an existing string inverter, you can keep that setup and add a Powerwall 3 as a separate AC-coupled unit. But for new solar installations, the Powerwall 3 is designed to be the only inverter in the system.

2. Check whether your system needs G98 or G99 DNO permission

This is where Powerwall 3 installations require careful attention. Because the integrated inverter can export at up to 5 kW AC, the combined solar and battery export capacity almost always exceeds the 3.68 kW per phase threshold for simple G98 notification. Most UK domestic Powerwall 3 installations therefore require a full G99 application.

A G99 application involves the installer submitting technical information about the inverter (the Powerwall 3 has been pre-approved by some DNOs, which speeds things up), the proposed export limit, and any protection settings. In Kent, the DNO is UK Power Networks. Processing can take four to six weeks.

Some installers offer to limit the inverter's export to 3.68 kW to qualify for G98 notification instead. This avoids the wait but means the system cannot export above 3.68 kW even when the battery is full and the sun is shining. Whether that trade-off makes sense depends on your system size and usage pattern. Ask the installer to confirm the DNO route in writing before you sign.

3. The physical installation: mounting, wiring and commissioning

The Powerwall 3 is a grey wall-mounted unit approximately 1.1 metres tall and 0.75 metres wide. At around 130 kg it is heavy, and it must be fixed to a structural wall, not a stud partition. The installer will check the wall beforehand and use an appropriate fixing system for your wall type (masonry, block or concrete).

Location matters for several reasons:

• It must be accessible for the installer during commissioning and for future maintenance
• PAS 63100 prohibits installation above a staircase or in a sleeping room
• It needs clearance from combustible materials (typically 300 mm on each side)
• It needs to be covered from direct driving rain, though the unit itself is IP67 rated

Common locations in UK homes are garages, utility rooms and external covered wall locations. Once mounted, the installer runs DC cable from the solar panels to the DC input on the Powerwall 3, an AC connection to the consumer unit or a dedicated isolator, and fits the CT clamp on the incoming supply tails to enable import and export monitoring.

4. Gateway 2 setup and app configuration

The Tesla Gateway 2 is supplied with the Powerwall 3 and is a separate small unit, usually mounted near the consumer unit. It handles communication between the Powerwall 3, your home network, and Tesla's servers. The installer will connect it to your router via Ethernet or Wi-Fi during commissioning.

Once the Gateway is online, your installer adds the system to a Tesla account - either one you create in advance or one set up on the day. You then download the Tesla app on your phone to see:

• Real-time solar generation
• Battery state of charge
• Home consumption
• Grid import and export

Operating modes can be set via the app. Self-powered mode maximises self-consumption. Time-based control charges from grid electricity at cheap overnight rates (useful on Octopus Go or Agile) and discharges during peak periods. Backup-only mode keeps a specified reserve for power cuts.

5. PAS 63100 fire safety compliance

PAS 63100 is the British Standards Institution's code of practice for the safe installation of electrical energy storage systems in domestic and commercial premises. In practice, for a residential Powerwall 3, this means:

• The installer carries out a fire risk assessment and documents it
• The chosen location is checked against the prohibited locations (above a staircase or in a room used for sleeping)
• Cable management and terminations meet the standard
• A commissioning sheet is completed and signed

PAS 63100 compliance is required for MCS certification of the installation. An installer who cannot produce the commissioning sheet has not completed the job properly.

BS 7671 Amendment 4 (April 2026) introduced Section 745 covering battery storage systems. Your installer must be aware of the new requirements, particularly around protection settings and disconnection under fault conditions. Ask for confirmation that the installation complies with Amendment 4.

6. Documents and certificates to keep

At the end of the installation day, you should receive:

• MCS certificate: The formal certification of the installation by an accredited engineer. You need this for any future warranty claim and for the Smart Export Guarantee.
• G99 DNO approval letter (or G98 notification reference, if applicable): Confirmation from UK Power Networks that export is permitted. Without this you are not legally allowed to export.
• Electrical Installation Certificate: Covering the new circuit from the consumer unit to the Powerwall 3 and any other electrical work done. Issued by a qualified electrician.
• PAS 63100 commissioning sheet: The fire safety and commissioning checklist signed by the installer.
• Tesla warranty documentation: The Powerwall 3 comes with a 10-year unlimited-cycle warranty from Tesla. Keep the registration confirmation from the Tesla app.

Store all of these together with your property deeds or in a safe place you will remember when you come to remortgage or sell. Buyers and their solicitors do ask for this paperwork, and missing documents are a common cause of delays.

When to call us

Richard covers the electrical side of solar and battery installations across Sandwich and east Kent: consumer unit upgrades ahead of a Powerwall installation, earthing assessments for TT properties, and EV charger connections. If your Powerwall installer needs a qualified electrician for the board work, or you want an independent check before the system is commissioned, get in touch.