Battery Degradation

Battery degradation is the inevitable decline in your battery's ability to store energy over time. Like a smartphone battery that holds less charge after a few years, home solar batteries slowly lose capacity through use.

Typical degradation rates for LFP lithium-ion batteries (the most common chemistry in home solar):

• Most manufacturers warranty 70–80% capacity retention after 10 years or a specified number of cycles
• Real-world LFP degradation at normal DoD: approximately 1–3% per year
• A 10 kWh battery may retain only 7–8 kWh of usable capacity after 10 years

Factors that accelerate degradation:

• High ambient temperature: batteries degrade faster in hot environments (garages in summer, uninsulated loft spaces)
• Deep discharging consistently to near 0%
• Frequent rapid charging
• Keeping the battery at near 100% charge for prolonged periods

Good battery management systems (BMS) automatically protect against the worst degradation patterns. Installing your battery in a cool, dry, ventilated location (such as a garage wall with shade, not a south-facing conservatory) can extend battery life significantly.

Build battery degradation into your financial model: a battery that delivers 10 kWh in year 1 will deliver roughly 7–8 kWh by year 10, reducing your annual savings accordingly.