Sonnen home battery installation: what the job involves

Video reference. "Sonnen Home Battery Installation (UK)" is from Electrician Life, a UK electrical channel following working electricians Jordan, Sam and Cory on commercial and domestic jobs. The video covers an AC-coupled Sonnen battery installation from consumer unit wiring through to CT clamp connection and commissioning, showing the practical steps of a real UK job rather than a product walkthrough.

1. Surveying the site and planning the supply circuit

Sonnen batteries are AC-coupled: they have an integrated inverter and connect to the household via a dedicated AC supply circuit from the consumer unit. Because there is no DC coupling, a Sonnen battery works alongside any solar inverter brand, or on its own without solar panels. This makes it a practical choice for retrofit installations where the existing inverter is from a different manufacturer.

The installer assesses the consumer unit for available ways, reviews the cable route from the consumer unit to the proposed battery location, and measures peak import current to confirm the supply fuse can accommodate the battery's charge and discharge rate.

2. Selecting the capacity and confirming the installation location

The Sonnen eco is available in modular capacities starting at 5 kWh; the sonnenCore+ comes in a range of fixed sizes. The installer sizes the system based on the household's daily electricity consumption, the solar array output where present, and whether the priority is maximising self-consumption, participating in a smart energy tariff, or having backup power available.

The installation location is agreed at this stage. Most Sonnen units are wall-mounted in a garage or utility room. The installer confirms the wall can carry the unit weight, that there is adequate ventilation clearance, and that the CT clamp cable can reach from the meter or consumer unit to the battery's meter connection port.

3. Preparing the mounting position and cable entries

The installer fits the wall bracket, checks that fixings are appropriate for the masonry type, and routes cable entry glands through the wall or enclosure before the unit is lifted into place. Getting the cable entry positions right before mounting avoids the need to re-drill with the unit in place. The operating temperature range is checked against the expected conditions in the installation space, particularly for garages that are unheated in winter.

4. Running and connecting the AC supply cable

A dedicated twin-and-earth cable runs from the consumer unit to the Sonnen terminal block. The conductor cross-section is selected to keep volt drop within the BS 7671 Regulation 525 limit, accounting for the route length and method of installation. All connections inside the Sonnen terminal enclosure are torqued to the values in the installation manual, and the cable is clipped and supported at the required intervals along the route.

5. Fitting the MCB at the consumer unit

The supply circuit is protected by an MCB sized to match the cable and the battery's rated charge and discharge current. Where the consumer unit uses RCBOs throughout, a standard MCB is sufficient for the new way. The installer verifies polarity and earth continuity before closing the board, and the circuit schedule is updated to label the new circuit clearly.

6. Installing and orienting the CT clamp

A current transformer clamp fits around the grid import conductor, typically at the consumer unit or the meter tails. Orientation is critical: fitting the clamp the wrong way round inverts import and export readings, so the battery charges from the grid when it should be discharging and exports when it should be storing. The signal cable routes to the Sonnen unit's meter input, and the installer checks the readings in the mySonnen app before commissioning proceeds.

7. Commissioning on mySonnen and notifying Part P and DNO

With all connections made and dead tests passed, the installer powers up the system and works through the mySonnen commissioning wizard. Charge and discharge schedules are configured for the household's energy tariff. Where the homeowner wants to join the Sonnen community tariff or another smart energy programme, the relevant settings are applied at this stage and verified against the CT clamp readings.

The installation is then notified through the installer's Part P competent person scheme; you receive an Electrical Installation Certificate. DNO notification follows: G98 self-certification for systems exporting up to 3.68 kW per phase, with the DNO notified within 28 days. Larger or three-phase systems need G99 pre-approval before the work starts. Keep the EIC and DNO notification letter with your property documents.

When to call us

Richard installs home battery storage systems across east Kent, including Sonnen and other brands. He handles the AC supply wiring, CT clamp, mySonnen commissioning, Part P certification and DNO notification. Get in touch for a free fixed quote.