Plan generator backup
A generator covers long cloudy spells, lets you choose fewer days of autonomy and a smaller battery, and helps lead acid banks get regular full charges.
How
- Use this step when the generator charges batteries through an inverter/charger. Use continuity-8 when the generator runs loads directly in an outage.
- Decide manual or automatic start. An auto start generator controlled by the inverter/charger allows the shorter autonomy values in step power-12.
- Size the generator to run the inverter/charger at its chosen charge rate plus any loads passed through at the same time, and follow the inverter maker's table. Example (Victron): minimum about 5 kVA for a 3,000 VA inverter/charger and 8 kVA for 5,000 VA, larger is better, inverter-type generators need about 30% more, and the AC input current limit is set to about 80% of the generator's output.
- For LFP, keep the generator charge rate within the battery limits (one guide suggests C/2 or lower).
- Choose fuel with the waste and safety modules in mind: diesel, petrol, propane or biogas each have storage and safety rules.
- Connect the generator only through the inverter/charger input or an approved transfer switch. Never backfeed house wiring through a socket.
- Place it outdoors, at least 20 feet (about 6 m) from doors, windows and vents, and fit carbon monoxide alarms in the home.
Safety: Generator exhaust contains carbon monoxide, which can kill in minutes. Never run a generator indoors, in a garage, crawlspace or shed, even with doors open.
Do these first
Sources
- Oversized PV array and battery days of autonomy in stand-alone power systems. GSES (Global Sustainable Energy Solutions), accessed 2026-11
- Everything you need to know to replace a lead-acid battery bank with LFP batteries. Solar Builder, accessed 2026-11
- Portable Generator Safety Alert. US Consumer Product Safety Commission, accessed 2026-11
- MultiPlus FAQ: generator sizing. Victron Energy, accessed 2026-11