Battery Storage Calculator

This calculator models home battery storage savings over 15 years. For time-of-use (TOU) rate structures, savings come from charging the battery at off-peak rates and discharging during on-peak hours (rate arbitrage). For flat-rate plans with solar, the battery captures excess solar generation for later self-consumption instead of exporting at a lower net metering rate. Battery capacity degrades annually (default 3%/year), while utility rates escalate at 3%/year. The federal Investment Tax Credit (ITC) of 30% applies to standalone battery storage under the Inflation Reduction Act. State incentives (e.g., California's SGIP) are applied when available. Net system cost equals the gross cost minus all applicable incentives. The payback period is the year when cumulative net savings first exceed zero.