Battery Storage Calculator
Size home battery systems like Tesla Powerwall, estimate backup duration during outages, and calculate potential savings from solar self-consumption and time-of-use rate arbitrage.
Battery System
Tesla Powerwall: 13.5 kWh
Including installation
80-100% for lithium batteries
85-95% typical
Your Home
US average: 30 kWh/day
Fridge, lights, WiFi: 2-5 kW
US average: $0.12/kWh
Peak hours rate
Solar Integration
Energy that would go back to grid
Home Batteries
Home battery storage systems store electricity for use during outages or peak rate periods. Popular options include Tesla Powerwall (13.5 kWh), Enphase IQ (5 kWh modules), and LG RESU (9.6-16 kWh).
- • Typical lifespan: 10-15 years
- • Degradation: ~2% capacity loss/year
- • 30% federal tax credit available
How to Use
- Enter your battery capacity and installed cost
- Set your daily energy usage and essential backup load
- Configure electricity rates and solar details if applicable
- Click Calculate to see backup duration and savings
FAQ
Do I need solar to benefit from a home battery?
No. While batteries pair well with solar, you can still save money through time-of-use arbitrage—charging during cheap off-peak hours and discharging during expensive peak hours. Batteries also provide backup power during outages.
How long will a battery power my home?
It depends on your load. A 13.5 kWh battery running essentials (fridge, lights, WiFi) at ~2 kW could last 6+ hours. Running AC or electric heat will drain it much faster. Most systems let you prioritize which circuits to back up.
What is depth of discharge (DoD)?
DoD is the percentage of a battery's capacity that can be used. Lithium batteries typically allow 80-100% DoD. A 13.5 kWh battery at 90% DoD provides 12.15 kWh of usable energy. Higher DoD means more usable capacity but may affect longevity.
Further Reading
Is Solar Worth It? 7 Factors That Make or Break Your ROI
Batteries pair well with solar—understand the full ROI picture.
Buy Solar Now or Wait? Tax Credit Analysis
Batteries also qualify for the 30% federal tax credit.
Generator Sizing Guide for Backup Power
Compare battery vs generator backup solutions.