Soft-start and surge check
Fridges, sump pumps, well pumps and air conditioners have a motor that draws its locked-rotor current (LRA) for a fraction of a second at start, often 3 to 7 times the running current. A station or generator must cover that moment as well as the running watts. Pick an appliance, then a station (verified specs only) or type your own limits.
Pre-filled
Fridge · Sump pump · Well pump · Mini-split · RV AC
How this is worked out
- Start-up VA = nameplate LRA × volts. With no LRA we use your start-up watts, or failing that 6 × running watts (a typical compressor figure, marked as an estimate).
- With a soft-start kit the peak is cut by the percentage you set (default 60%, a planning assumption, not a measured result; kits and motors differ, so check the kit maker's spec page). We never plan it below 1.5 × running VA.
- A 10% margin is added and the surge need rounds up to the next 100 W. If a maker gives no surge rating we compare against the continuous rating.
- 240 V loads need a 240 V output. Well pumps often need a transfer arrangement set up by an electrician; see the transfer switch chooser.
- Appliance presets are typical values for planning, not your model. Read your own label. Inverter-driven units (many mini-splits, newer fridges) start more gently than the typical figure.
Related: sump pump guide · fridge guide · backup power calculator. We list no prices and have not hands-on tested any product.