Solar Battery Calculator
Determine how many batteries you need for home backup power. Factor in daily energy usage, desired backup duration, and depth of discharge.
US average: ~30 kWh/day
Duration of backup power
Capacity of each battery unit
Typical: 80-90% for lithium-ion
Frequently Asked Questions
How many batteries do I need for my house?
The average US home uses about 30 kWh per day. For a full day of backup with a 13.5 kWh battery (like the Tesla Powerwall) at 90% depth of discharge, you would need about 3 batteries. For essential loads only (10-15 kWh), 1-2 batteries are usually enough.
What is depth of discharge (DoD)?
Depth of discharge is the percentage of battery capacity that can be used before recharging. Most lithium-ion batteries have a DoD of 80-90%. A 13.5 kWh battery with 90% DoD provides 12.15 kWh of usable energy.
How long will a solar battery last?
Most home solar batteries come with a 10-year warranty and can last 10-15 years. Lithium-ion batteries typically retain 70-80% of their original capacity after 10 years of regular cycling.