Depth of Discharge Calculator
How does DoD affect your battery's usable capacity, cycle life, and real cost? Enter your specs — see the numbers.
How to Use This Calculator
Enter your battery capacity
Type the nameplate capacity of your battery in kWh — this is the total capacity printed on the spec sheet, not the usable capacity. For example, a Tesla Powerwall 3 has a 13.5 kWh nameplate capacity.
Set depth of discharge
Choose your operating DoD percentage. This is how deeply you drain the battery before recharging. The preset options show recommended ranges: 50% for lead-acid, 80% for LiFePO4. A higher DoD gives more energy per cycle but reduces total lifetime cycles. Many manufacturers publish a cycle life curve — always check it.
Enter the cycle life at your DoD
The cycle life field is critical. Most battery specs list cycles at a specific DoD. LiFePO4 batteries might be rated 3,500 cycles at 80% DoD but only 2,000 cycles at 100% DoD. Use the value from the manufacturer's datasheet for the DoD you selected. This directly affects the lifetime throughput and cost-per-kWh calculation.
Add battery cost for economics
Enter the battery purchase price to see cost per lifetime kWh — the most useful metric for comparing battery chemistries and sizes. A cheap lead-acid battery that only lasts 500 cycles often costs more per kWh throughput than an expensive LiFePO4 with 3,500 cycles.
The Formula
The cost per lifetime kWh metric is the best way to compare batteries. It accounts for both the upfront cost and how long the battery actually lasts. A $1,800 LiFePO4 at 3,500 cycles × 8 kWh usable = 28,000 kWh throughput → $0.064/kWh. A $800 lead-acid at 500 cycles × 5 kWh usable = 2,500 kWh → $0.32/kWh. The LiFePO4 is 5× cheaper per unit of energy delivered over its lifetime.
Example
Comparing lead-acid vs LiFePO4 — same $2,000 budget
The LiFePO4 delivers 46× more energy over its lifetime at 5× lower cost per kWh. This is why lithium has almost entirely replaced lead-acid for solar storage despite higher upfront cost.