Inverter clipping
Energy lost when the DC power available from a PV array exceeds the inverter AC rating, so the inverter caps output at its maximum.
When a PV array is oversized relative to its inverter, which is normal practice (see DC/AC ratio), there are hours of high irradiance and cool temperatures when the array could deliver more than the inverter can convert. The inverter then moves the array off its maximum power point to limit input, and the production curve shows a flat top around midday: the clipped energy.
Clipping losses depend on DC/AC ratio, climate, orientation and tracking:
- DC/AC 1.1–1.2 on fixed-tilt systems in central Europe: usually under 1% of annual energy.
- DC/AC 1.3 on single-axis trackers in sunny climates: about 1–4%.
- DC/AC 1.5 and above: 5–10% or more, justified only when modules are very cheap or grid capacity is constrained.
Accurate estimates require hourly or, better, sub-hourly simulation, because hourly averages smooth out short irradiance peaks and understate clipping. Cold, clear days with cloud-edge enhancement can push instantaneous DC power above the module STC rating.
Clipped energy is not necessarily wasted: DC-coupled battery systems can store it before the inverter, which is a key argument for DC coupling in hybrid PV-plus-BESS plants. Clipping is distinct from grid curtailment, which is imposed externally by the system operator.
Related terms
All terms →- DC/AC ratio
Ratio of a PV array DC nameplate capacity at STC to its inverter AC rating; also called inverter loading ratio (ILR).
- String inverter
An inverter that converts the DC output of one or more series strings of PV modules into grid-synchronised AC, typically with several independent MPPT inputs.
- Curtailment
Deliberate reduction of a generator’s output below what it could produce, usually wind or solar, because of grid, market or system constraints.
- BESS (Battery Energy Storage System)
A complete grid- or site-connected battery installation, including cells, battery management, power conversion, thermal management and controls.
- Performance ratio
Ratio of actual AC energy output to the theoretical output implied by plane-of-array irradiation and nameplate capacity; a location-independent quality metric for PV plants.