List everything you expect to run off the inverter at the same time. Surge multiplier is the startup spike: resistive loads like a kettle are 1x, motor loads and compressors are commonly 1.5x to 3x. Use the figure in your appliance manual when you have it.
Add your loads
Enter running watts for each appliance.
Assumptions and limits
- The recommended figure is AC output. Inverter efficiency (88% assumed) is charged to the DC input side, so DC draw is higher than the AC load. Real units run roughly 85–93% depending on load point.
- DC draw estimated at 12.6 V nominal. Actual draw rises as battery voltage falls.
- Continuous AC rating is rounded up to the next 100 W.
- Worst-case surge assumes the largest single startup spike occurs while every other listed load is already running. That is the realistic case; a motor rarely starts into an idle bus.
- Surge capability varies by model and by surge duration. This tool reports the surge your loads demand; it does not tell you whether a given inverter can sustain it.
- Does not size wiring, fusing, or battery bank. Use the battery calculator and confirm wire gauge against the inverter manual.
This is a planning estimate, not an engineering specification. Confirm every figure against the manual for your exact equipment. Wire gauge, fuse sizing, and breaker sizing are safety items. If you are not certain, have a qualified RV technician or electrician verify the install.