What size generator for a heat pump?
Pick your heat pump size
The watts shown are simple amps × volts arithmetic from the spec sheet's compressor amps. They are a planning estimate, not a wattage Goodman publishes, and they leave out the outdoor fan motor and any indoor air handler or backup heat strips.
Goodman GSZH5 compressor amps by size
| Size | Model | Compressor RLA | Compressor LRA | Min. circuit ampacity | Max. overcurrent protection (A) |
|---|---|---|---|---|---|
| 1.5 ton | GSZH501810 | 9.0 | 42.6 | 12.2 | 20 |
| 2 ton | GSZH502410 | 11.5 | 59.5 | 15.3 | 25 |
| 2.5 ton | GSZH503010 | 14.1 | 67.9 | 18.6 | 30 |
| 3 ton | GSZH503610 | 16.0 | 91.9 | 22.8 | 35 |
| 3.5 ton | GSZH504210 | 17.7 | 110.2 | 23.4 | 40 |
| 4 ton | GSZH504810 | 19.9 | 110.0 | 26.2 | 45 |
| 5 ton | GSZH506010 | 25.6 | 151.0 | 33.0 | 50 |
Source: Goodman GSZH5 heat pump specifications (electrical data table), 208/230 V, 1-phase, 60 Hz units.
What the numbers mean for a generator
RLA (rated load amps) is the compressor's running current. LRA (locked-rotor amps) is the current it can pull for a moment as it starts, before the motor is turning. The generator has to carry the starting moment, not just the running amps, on top of everything else that is already on.
These are 208/230 V units. A generator or inverter that only puts out 120 V can't run them at all, no matter its wattage. You need a 240 V output and a transfer switch rated for the circuit. See transfer switch sizing.
Many heat pumps also have electric backup heat strips in the indoor unit. Those are a separate, large load and are not in this table. Check your air handler's nameplate.