What Size Battery Do I Need for a 2000W Inverter?
Size a battery bank for a 2,000W inverter using actual load, runtime, bank voltage, BMS current and inverter efficiency.
A 2,000W inverter rating does not mean you need to run 2,000W continuously. Battery capacity should follow the actual load profile, while BMS and current capability must still support peak demand.
A 2,000W inverter does not dictate one battery capacity. The inverter rating tells you the maximum power class; battery capacity tells you runtime. You also need enough battery/BMS current capability to support the inverter at the chosen bank voltage.
What matters
- Separate inverter maximum power from typical appliance load.
- Higher bank voltage reduces current for the same AC power.
- Battery BMS limits must support the inverter demand.
- Capacity determines duration; current capability determines whether the load can run.
Decision factors that change the answer
Runtime target
Two hours at a 1,000W average load needs roughly 2kWh delivered energy before losses and reserve.
Bank voltage
The same 2,000W load draws far more current from a 12V bank than from a 24V or 48V bank.
BMS current
A battery can have enough Wh but still trip if its discharge-current limit is below the inverter demand.
Actual load
Most systems do not run continuously at the inverter’s maximum rating. Size energy from the real average load.
How to size it
- Define the largest simultaneous AC load.
- Set desired runtime at that load.
- Convert required AC energy to battery Wh with efficiency allowance.
- Verify bank/BMS current against the inverter demand.
A 1,000W load for two hours requires roughly 2kWh of delivered AC energy before inverter losses and reserve.
Worked example
At a 1,000W average AC load for three hours, you need about 3kWh delivered. Assuming 90% inverter efficiency and 15% reserve, nominal storage may need to be around 3.9kWh. The exact battery configuration still depends on voltage and current limits.
Common buying mistakes
- Buying battery Wh while ignoring current limits.
- Assuming a 2,000W inverter always draws 2,000W.
- Undersizing cabling/protection in DIY systems.
Size capacity from runtime and size electrical current capability from the inverter; both constraints must be satisfied independently.
Check the underlying numbers
Use these site resources to replace generic assumptions with your own load or the source-linked data behind this guide.
Use the numbers before choosing a model
Start with your load list. The battery needs enough watt-hours for the desired runtime and enough continuous/surge watts to operate the appliances at the same time. Then check whether your recharge method can replace the energy you expect to consume.
For outage planning, we recommend keeping reserve capacity instead of designing a system that reaches 0% at the end of the forecasted outage.
Next step
Estimate battery runtime → or Build a critical-load energy budget →.