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Inverter efficiency and conversion losses
Inverter3 min readUpdated: 2026-08
Every DC → AC conversion dissipates energy as heat. A modern inverter's efficiency ranges from 90% to 97%, but it is not constant — it drops sharply at low load and near maximum power.
E_AC = E_DC × η_inverterη varies with load ratio — use a curve, not a single value
| Load ratio | Typical efficiency | Note |
|---|---|---|
| < 10% | 70–85% | Low load: standby draw weighs proportionally more |
| 20–80% | 93–97% | Optimal efficiency zone |
| > 90% | 88–93% | Near the limit, internal heating |
An inverter's standby draw — often 5 to 15 W — runs 24/7 even with no load. On an off-grid system with low nighttime consumption, this loss can represent 5–10% of the daily energy balance.
SolarDim Pro applies inverter efficiency to the daily energy balance (E_pv = kWp × PSH × η_system). A cheap inverter at 88% instead of 96% efficiency forces the PV array to be oversized by roughly 9% for the same result.
Common mistakes
- Using the "peak" efficiency from the datasheet for the whole energy balance
- Forgetting standby draw on a system with low nighttime load
- Undersizing the inverter, which then runs near 100% continuously and shortens its lifespan