Path-Q Solar
What battery inverter power and surge ratings are needed to start high-power equipment during an outage?
Answer
The inverter must support the equipment's continuous running power and its starting surge, while also handling other loads that operate at the same time. Use measured or manufacturer data for the specific motor, compressor, pump, or heater; generic appliance labels are not sufficient for a reliable design.
Key points
- Starting demand can be several times a motor's running demand and may last briefly.
- The battery and inverter must support both surge duration and voltage or frequency behavior required by the equipment.
- Staggering starts or using soft-start equipment can reduce the required peak rating.
What it depends on
- Equipment running and locked-rotor or starting current
- Duration of the starting surge
- Other simultaneous loads
- Inverter continuous, surge, and overload specifications
- Battery voltage and ability to sustain the demand
Risks and trade-offs
- An undersized inverter may trip, fail to start equipment, or shorten equipment life.
- An oversized system costs more and may operate inefficiently at light loads.
- Some loads require specialist review because their startup behavior is difficult to infer.
Information you may need
- Equipment nameplate and manufacturer starting data
- Measured startup current where appropriate
- Inverter continuous and surge specifications
- A schedule of simultaneous outage loads
Your next step
What to do next
Have the installer perform a documented load and surge calculation for the specific equipment, including worst-case simultaneous starts.
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SQ01034