- Question
How Long Does A 42kWh Battery Last?
Runtime by household size, blackout backup duration, and cycle-life expectancy for a 42 kWh home battery in Australia.
- Quick answer
A 42 kWh home battery lasts ~2 days for an average home, 8–12 hours of whole-home backup during a blackout, and 10+ years of daily cycling.
Runtime by household usage
| Home type | Daily use | 42 kWh runtime |
|---|---|---|
| 1-bed apartment | 8 kWh/day | 5+ days |
| Small family (2-3 bed) | 15 kWh/day | ~2.8 days |
| Average Australian home | 20 kWh/day | ~2 days |
| Large all-electric home | 35 kWh/day | ~1.2 days |
| All-electric + EV + pool | 50–60 kWh/day | ~16–20 hours |
Blackout runtime
Running only essential circuits (fridge, lights, internet, phone charging — ~1.5 kW average draw), 42 kWh delivers 24–36 hours of backup. Running the whole home (~3–5 kW average), it lasts 8–12 hours. When paired with solar, daytime blackouts extend backup indefinitely because the battery recharges from the sun.
Cycle life
- Runtime FAQs
42 kWh runtime FAQs
How long does a 42kWh battery last?
A 42 kWh battery lasts roughly 2 days for an average Australian home (20 kWh/day), 1 day for a large all-electric home (35–40 kWh/day) with ducted AC and EV charging, or 12-24 hours or more of backup power for running essential appliances during a blackout, depending on your energy usage and battery capacity. Designed with a 10+ year cycle life based on one full charge and discharge cycle per day, providing reliable long-term battery performance.
How long does 42kWh last during a blackout?
In blackout backup mode, 42 kWh will run essential circuits (lights, fridge, internet,) for 24–36 hours, or the whole home for 8–12 hours. If solar is producing, backup runtime extends indefinitely during daylight.
How many years will a 42kWh battery last?
10+ years. Fox ESS CQ7-L6 (the standard 42 kWh system) is warranted for 10 years at 60% capacity retention. Real-world LFP batteries typically last 12–15 years with daily cycling before dropping below usable capacity.