Solar & Inverter Battery Bank Calculator
Find the battery size you need to keep your appliances running during a power outage. Choose your appliances, set how many hours you need them to run, and get a recommended battery bank.
Check Your Battery Backup Time
Enter the battery you already have, then select the appliances you want to run at the same time. We will estimate how long the battery can power that load.
Appliances you want to run together
Use the actual wattage from the appliance nameplate when available. These values are planning estimates.
Your Estimated Backup Time
Based on the battery capacity and appliances you entered.
What This Means
1. Choose Your Battery & System
2. Select Your Appliances & Backup Time
Enter how long you want each appliance to run from the battery after power goes off. You can change the wattage if your actual appliance has a different rating.
Understand Your Battery Recommendation
Battery size is mainly about how much energy your selected appliances need and how long you want them to run when there is no solar power.
Why did the calculator give me this result?
We use your selected appliances, backup hours, battery type and system voltage to estimate the storage and battery-bank configuration needed.
Learn the technical details
A battery's kWh or Ah rating does not automatically equal the number of hours it will run your appliances. Usable capacity, inverter losses, battery age and discharge limits all matter.
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Battery Calculator FAQs
Common questions about solar battery capacity and backup time.
What does the battery calculator help me work out?
It estimates the battery storage needed for the backup appliances and hours you enter. It can also show a battery-bank configuration based on the selected battery voltage and type.
What does battery backup hours mean?
It means how long the selected appliances should run from the battery when solar is not supplying the load. For example, 6 hours of backup means the selected backup load is planned to run for about six hours from the battery.
Does a 10kWh battery give me 10 hours of backup?
Not automatically. Backup time depends on the load, usable battery capacity, inverter losses and the battery’s recommended depth of discharge. A 10kWh battery running a 2kW load will not give the same backup time as when running a 500W load.
Which is better for solar: lithium or tubular batteries?
Both can be used in solar systems, but they have different costs, usable capacity, cycle life, charging requirements and maintenance needs. Lithium batteries usually offer higher usable capacity and longer cycle life, while tubular batteries can have a lower upfront cost. Check the manufacturer’s specifications for the exact model.
Why can the actual backup time be different from the calculator?
Real battery performance can change with battery age, temperature, discharge rate, inverter efficiency, wiring losses, battery quality and the actual load. The calculator should therefore be used for planning rather than as a guarantee of runtime.
How do I know how many batteries I need?
First calculate the total usable energy you need for your backup period. Then choose a battery type and voltage and check the usable capacity of the exact battery model. The number of batteries also needs to match the inverter’s required battery voltage and the battery manufacturer’s connection limits.