Off-grid generator integration Sizing, auto-start, and charging done right

Set 30–60 minutes. This prevents the generator starting, bringing the battery above the stop SoC quickly, and shutting down — then repeating on the next SoC dip. Short-cycling wears the engine starter motor and prevents the battery from completing a full charge cycle. On Victron: Settings → Generator start/stop → Minimum run time.

Set a backup voltage start condition (e.g. 46.0V on a 48V LiFePO4 system) for cases where the SoC estimate drifts. The voltage trigger acts as a safety net regardless of displayed SoC.

Raise the start SoC to 35–40% in winter to account for cold-weather capacity loss and reduced solar generation. See our cold weather battery performance guide for the full picture on winter system settings.

On Victron Cerbo GX, you can add quiet-time conditions to block auto-start between set hours (e.g. 22:00–07:00) so the generator never starts at night automatically. Manual override remains available.

In UK summers, many off-grid systems rarely need the generator. Run it under meaningful load for 30–60 minutes every two to four weeks: this keeps the alternator charged, circulates fresh oil through the engine, prevents fuel gumming in the carburettor (petrol), and ensures it will start reliably when needed. Use a fuel stabiliser in any petrol stored for more than four weeks.

Never operate a generator indoors, in a garage, or in any enclosed or semi-enclosed space. Carbon monoxide is odourless and lethal. Fixed generator enclosures must be vented with sufficient air flow for combustion and cooling. Install CO detectors in any adjacent habitable spaces. Site the exhaust to discharge away from windows, doors, and air intakes. For a generator in a purpose-built acoustic housing, ensure the enclosure is MCS or manufacturer-approved for the generator model.

Petrol and diesel are Class II and Class IIIA flammable liquids under DSEAR regulations. Storage in excess of 30 litres outside a dwelling requires consideration of DSEAR risk assessments. Fixed generator enclosures or outbuildings housing generators may require planning permission if they exceed permitted development limits — check with your local planning authority before constructing a permanent installation.

Petrol generators: engine oil every 50–100 hours or annually, air filter every 100 hours, spark plug every 200 hours. Diesel generators: engine oil every 100–200 hours, fuel filter annually, coolant every two years (liquid-cooled models). Keep a written service log — it matters for insurance and warranty claims.