Off-grid systems have no utility cushion—your inverter is the entire AC bus. This off-grid inverter capacity estimator turns peak load watts and a planning margin into a continuous watt target for cabins, RVs, and solar-backed homesteads.
Benefits
- Estimates continuous inverter W from off-grid peak load.
- Applies margin for surge, loss, and modest load growth.
- Frames capacity before battery C-rate and solar yield checks.
How it works
- List AC loads that run together on the off-grid bus.
- Enter total peak watts and a safety margin percent.
- Read estimated inverter capacity—compare to hybrid or stand-alone SKUs.
FAQ
What does an off-grid inverter capacity estimator do?
It projects minimum continuous inverter watts for sites without grid backup: capacity ≈ peak load W × (1 + margin ÷ 100). Example: 1,500 W cabin peak at 30% margin → ~1,950 W continuous class inverter before checking surge for well pumps or fridge compressors.
How is off-grid sizing different from grid-tied backup?
Off-grid inverters run 24/7 from batteries—no utility pass-through. Peak scenarios include cloudy evenings when solar is low and loads stack higher. Estimate capacity from realistic simultaneous use, then confirm the battery bank can deliver the amps at your DC voltage.
Should I include charger pass-through in capacity?
Hybrid off-grid inverters may add shore or generator charging on the same unit. Capacity for AC loads still follows peak W plus margin; charger amps are a separate column on the datasheet. Size continuous watts first, then verify MPPT or charger limits match your solar array.
Technical specifications
- Estimated capacity W = peak_W × (1 + margin% ÷ 100).
- Off-grid peak = simultaneous AC running watts.
- Check surge W for largest motor on the bus.
- Related: inverter-sizing, battery-bank-size, rv-solar-calculator.
Off-grid capacity starts at the evening peak
Without grid support, the inverter must cover every AC watt you refuse to shed. An off-grid inverter capacity estimator begins with the heaviest simultaneous load—often cooking, refrigeration, and pumps after sunset—then adds margin. Underestimating here means load shedding or nuisance trips when batteries are already stressed.
Continuous watts are the planning anchor
Estimated capacity targets continuous rating on the label, not brief surge alone. Solar-hybrid units list charger and MPPT limits separately; AC capacity still follows peak load math. A 3,000 W continuous class inverter with adequate surge handles most cabin peaks better than a 2,000 W unit with high surge but low continuous.
Pair capacity with storage and array
Inverter watts do not replace battery amp-hours or panel kilowatts—they define the AC ceiling. After capacity is estimated, check that the bank can supply DC amps at your bus voltage and that daily Wh replenishment matches use. Chain to RV Solar Calculator or Battery Bank Size when the question shifts from AC headroom to overnight autonomy.