Calculating performance metrics

Capture Price (£/MWh), Capture Rate & Profile Delta (£/MWh)

Capture Price (£/MWh), Capture Rate & Profile Delta (£/MWh) are all measures of a solar asset’s market value capture, indicating how its generation profile translates into revenues relative to the average wholesale electricity price.

Capture price is the generation-weighted average wholesale price received by solar generation.

Capture Price = ∑(Unclipped Generationₜ × WholesalePriceₜ) ÷ ∑Unclipped Generationₜ

Where unclipped generation is solar generation that remains below the grid connection or inverter limit. Any generation that exceeds the grid or inverter limit cannot be exported to the grid and is 'clipped'.

In sunny periods, where abundant solar generation lowers midday prices, solar capture price can be significantly lower than average wholesale power price.

Capture rate for a given period is simply the ratio between the solar capture price and average wholesale power price.

Capture Rate = Capture Price ÷ Average Wholesale Market Price

Profile Delta (£/MWh) is the difference between the capture price and the average wholesale market price. A positive delta indicates solar generation consistently aligns with higher-priced hours, while a negative delta indicates lower-price alignment.


Profile Delta = Capture Price − Average Wholesale Market Price

Solar Load Factor (%) and Specific Production (kWh/kWp/year)

Solar load factor and specific production are both measures of a solar system’s performance, quantifying the actual energy output relative to its installed capacity.

Specific production is calculated as total annual solar generation divided by the installed DC capacity.


Specific Production = Total Annual Unclipped Generation (KWh) ÷ Installed Capacity (kWp)

Solar load factor is total solar generation for a period expressed as a percentage of the theoretical maximum generation for that period.


Load Factor = (Total Unclipped Generation in period ÷ (DC Solar MWp × hours in period)))