Battery Cycle Life Calculator

About the Battery Cycle Life Calculator

Every battery has a finite number of charge-discharge cycles before it degrades below useful capacity (typically defined as 60–80% of original). The rated cycle life at a given depth of discharge tells you how many full cycles the battery can perform over its lifetime.

For solar applications, most home batteries cycle about once per day — charging from solar during the day and discharging at night. Some configurations cycle more (time-of-use arbitrage) or less (backup-only use). The cycling frequency directly determines how many years the battery will last.

This calculator converts the manufacturer's rated cycle count into an expected lifespan in years based on your cycling pattern. A battery rated for 6,000 cycles at one cycle per day would last about 16.4 years — well beyond most warranties.

When This Page Helps

Knowing your battery's expected lifespan in years helps you plan replacement costs, compare battery options, and evaluate the lifetime economics of a solar-plus-storage system.

How to Use the Inputs

1. Enter the manufacturer's rated cycle life (found in the spec sheet).
2. Enter the number of cycles per day (typically 1 for solar storage).
3. Optionally enter the number of cycling days per year.
4. Review the estimated lifespan in years.

Example Calculation

Tips & Best Practices

• LFP batteries offer 5,000–8,000 cycles; NMC typically offers 3,000–5,000.
• Backup-only batteries cycle infrequently, lasting decades in terms of cycle count.
• Higher DoD reduces cycle count — check the rating at your intended DoD.
• Calendar aging also limits life: 15–20 years maximum regardless of cycle count.
• Temperature extremes accelerate degradation beyond cycle count predictions.
• Most batteries retain 60–80% of original capacity at rated end-of-life.

Cycle Life by Chemistry

Lithium iron phosphate (LFP): 5,000–8,000 cycles at 80% DoD. Lithium NMC: 3,000–5,000 cycles at 80% DoD. Lead-acid (AGM): 500–1,000 cycles at 50% DoD. Lead-acid (flooded): 1,000–2,000 cycles at 50% DoD. Saltwater: 3,000+ cycles at 100% DoD.

Cycling Patterns in Solar Storage

A typical grid-tied solar battery cycles once per day: charging during solar hours, discharging in the evening/night. TOU arbitrage may add a second partial cycle. Backup-only batteries may go weeks without a full cycle, dramatically extending their cycle-based lifespan.

End-of-Life Planning

Batteries don't fail suddenly — they gradually lose capacity. Monitor your battery's state of health through the manufacturer's app. Plan for replacement when capacity drops below 70% or when it no longer meets your nightly energy needs.

Frequently Asked Questions

• What counts as one cycle?

  One full cycle is a complete discharge and recharge of the usable capacity. Two partial cycles (50% each) count as one full cycle. Batteries track cumulative energy throughput rather than discrete discharge events.

• How many cycles does a Powerwall last?

  Tesla warranties the Powerwall with a 10-year capacity-retention commitment. Real-world life still depends on depth of discharge, temperature, and annual energy throughput. For planning purposes, treat the warranty as a floor and use your cycling assumptions to estimate the likely service life beyond that period.

• Does partial cycling extend battery life?

  Yes. Shallow cycles (30–50% DoD) cause less stress than deep cycles. A battery rated for 4,000 cycles at 80% DoD might last 8,000+ cycles at 40% DoD. This is why some systems limit cycling depth below maximum.

• What is calendar aging?

  Batteries degrade over time even without cycling, due to internal chemical reactions. Calendar aging typically limits lithium batteries to 15–20 years regardless of cycle count. A battery that's rarely cycled won't last forever.

• When should I replace my battery?

  Replace when capacity drops below your minimum requirement (usually 60–80% of original). If your 13.5 kWh battery drops to 9 kWh usable and you need 12 kWh, it's time. Most homeowners replace after 10–15 years.

• Are battery replacement costs dropping?

  Battery costs have generally trended lower over time, but future replacement pricing depends on chemistry, manufacturing capacity, trade conditions, and installation costs. It is reasonable to expect the replacement market to look different by the time your battery wears out, but not to assume a specific future price.