How Long Does a 10kWh Battery Last？

A 10kWh residential battery's runtime depends on load power draw, efficiency losses, depth of discharge, and battery chemistry (typically LiFePO4 for homes). Expect 4-20 hours continuous use, but real scenarios vary widely.

Usable Capacity

Only 8-9kWh is practically available from 10kWh nominal. LiFePO4 allows 90-100% DoD safely, but systems lose 5-10% to inverter efficiency and BMS overhead.

Load Power Calculation

Runtime = Usable Capacity ÷ Load Watts. Here's how common household loads perform:

Load Scenario Power Draw Runtime (hours) Daily Energy Used

LED lights + WiFi + Fridge 200W 40-45h 8-9kWh

+ Small TV + Phone Charging 400W 20-22h 8-9kWh

+ AC (1.5HP) + Microwave 2,000W 4-4.5h 8-9kWh

EV Level 2 Charging 7,200W 1.1-1.25h 9kWh

Whole Small House (Peak) 5,000W 1.6-1.8h 9kWh

Peak vs. Average Power

Peak power matters more than total kWh. A 10kWh battery might deliver 5-10kW continuous, 15kW surge (10s). Insufficient peak power causes overload shutdown even with "full" capacity.

Daily Solar Replenishment

With 5kW solar array:

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Sunny day: Full recharge in 2-3h (14-18kWh input)

Cloudy day: 40-60% recharge (4-6kWh)

Runtime extends indefinitely with daily solar input matching consumption.

Efficiency Losses Breakdown

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Nominal: 10kWh

Round-trip efficiency: 92-95%

Inverter losses: 5-8%

BMS overhead: 1-2%

Wiring/heat: 1-3%

Usable output: ~8.5-9kWh

Temperature Derating

Hot/cold reduces output 20-50%:

Temperature Capacity Available Max Power Output

25°C (Ideal) 100% 100%

40°C 85-90% 80-85%

0°C 70-80% 60-70%

-10°C 50-60% 40-50%

State of Charge Management

Smart systems limit usable range for longevity:

Daily solar: 20-90% SoC = 7kWh usable

Emergency backup: 0-80% SoC = 8kWh usable

Max capacity: 0-100% = 9kWh usable

Real Household Examples

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Essential loads only (fridge/WiFi/lights): 18-24h runtime

Average 3-person home (Thailand): 8-12h

High AC usage (45°C summer): 3-5h

Off-grid mountain cabin: 24-48h

Cycle Life Impact on Runtime

Capacity degrades predictably:

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Year 1: 100% (9kWh usable)

Year 5: 92% (8.3kWh usable)

Year 10: 85% (7.6kWh usable)

Year 15: 75% (6.8kWh usable)

Bottom Line: Plan for 8-12 hours average household runtime with 10kWh LiFePO4, assuming 400-800W loads. 

Solar recharge extends this indefinitely. Size batteries 2-3x daily needs for reliability.

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