Home energy storage solutions

P Peter Lu Energy Storage Product Manager, GreenMore "How long does a 10 kWh battery last?" usually means one of two things: how many hours it powers the house during an outage, or how many years it lasts before replacement. The answers are different, and both start with the same distinction — a 10 kWh nameplate rating is not 10 kWh of usable energy. Nameplate vs usable capacity Batteries are not fully discharged in normal use. Repeatedly draining to zero accelerates wear, so manufacturers specify a depth of discharge (DoD) limit. For a typical LiFePO4 home battery, DoD is around 90–95%. Usable capacity = nameplate capacity × DoD A 10 kWh battery at 90% DoD delivers about 9 kWh of usable energy. Inverter efficiency (commonly 90–95%) reduces the energy reaching your outlets a little further, to roughly 8–8.5 kWh in practice. Always check which figure a seller quotes. Two "10 kWh" batteries can offer different usable energy if their DoD limits differ. The basic runtime formula Runtime (hours) = usable capacity (kWh) ÷ total load (kW) So the same 10 kWh battery lasts a long time powering a few low-wattage devices and a short time running the whole house. Individual appliances illustrate the point: Load Power Runtime on ~9 kWh usable LED lighting (several rooms) 100–300 W 30–90 hours Refrigerator 100–200 W while cycling 1–2 days (compressor cycles on and off) Router, TV and computer 150–300 W 30–60 hours Microwave 1,000 W About 9 hours of actual running time Air conditioner 1,000–2,000 W 4–9 hours These are single-load illustrations. In a real outage, several devices run at once and the hours add down, not up. Realistic outage scenarios Scenario Typical combined load Runtime on a 10 kWh battery Essential circuits only — fridge, lights, router, heating controls 400–800 W Roughly 11–22 hours Comfortable evening at home — cooking, TV, multiple rooms lit 1.5–2.5 kW Roughly 3.5–6 hours Whole home including air conditioning 3–5 kW Roughly 1.5–3 hours This is why a 10 kWh battery is usually paired with a critical-load panel rather than the whole house: covering everything at normal consumption empties it quickly. Schematic diagram of integrated photovoltaic, energy storage and charging system in residential buildings Solar changes the answer All the figures above assume no recharge. With solar, the battery refills during the day, so an outage is measured in weather and generation, not just in stored hours. A 10 kWh battery with a properly sized array can sustain essential loads through several days of interrupted grid supply — provided the inverter supports off-grid solar charging and the outage includes sunny days. In ordinary day-to-day operation, the battery is rarely emptied at all. The typical pattern is one partial cycle per day: charge from solar or off-peak grid, discharge over the evening, and start again the next morning. That routine matters for the second meaning of "how long it lasts". How many years does a 10 kWh battery last? LiFePO4 home batteries are commonly warranted for 10 years or a specified number of cycles, whichever comes first, with a capacity-retention guarantee (often around 70–80% of original capacity). The real service life depends on how the battery is treated: Cycle depth. Shallow daily cycles cause less wear than regular full discharges. Temperature. Batteries kept in a cool, dry space within the manufacturer's range last longer; sustained heat is the main enemy. Charge and discharge rate. Staying within rated C-rates avoids heat and cell stress. Cycle-life figures are only comparable when their DoD and test conditions are stated. A headline cycle count without those conditions does not tell you much. Is 10 kWh the right size? For a typical family focused on evening self-consumption and short-outage backup, 10 kWh is a common middle ground. If your outages are long and frequent, or you want whole-home coverage, 15–20 kWh or a modular system you can expand later is more appropriate. Size from your own load list rather than from average-household tables. Browse storage options on the products page and the home energy storage category page. For choosing what to back up, see the guide on choosing a home backup power system, and for larger capacity, the breakdown of 20 kWh battery costs. For help with a load list, use the contact page. FAQ Can a 10 kWh battery run a house for 24 hours? Only if the house draws about 350 W or less on average over the day — roughly essential loads like fridge, lighting, internet and heating controls. Normal whole-house consumption of 2–5 kW during waking hours empties a 10 kWh battery in a few hours. With solar recharging the next day, 24-plus hours of essential-load coverage is realistic. Why does my 10 kWh battery only show about 9 kWh available? Because of the DoD limit. The battery reserves roughly 5–10% to protect the cells, and the inverter consumes a little energy in conversion. Nameplate and usable capacity are different figures by design. How long will a 10 kWh battery run a refrigerator? A modern fridge cycles on and off and uses roughly 1–1.5 kWh per day, so a 10 kWh battery can keep it running for several days if it is nearly the only load. Add lights, internet and heating controls, and that drops to about a day of outage coverage. Will a 10 kWh battery last long enough to be worth it? In normal solar-plus-storage use — one shallow daily cycle — a LiFePO4 battery is typically designed for roughly 10 years or more of service and is warranted on that basis. Keep it within its DoD, C-rate and temperature ranges, and the battery should reach its warranted capacity retention without unusual degradation. P Written by Peter Lu — Energy Storage Product Manager, GreenMore Peter helps households and installers translate load lists and outage history into battery capacity, and explains usable capacity, DoD and cycle conditions in plain terms so quoted runtimes match real-world use.