The DC/AC ratio determines how an inverter operates relative to the array output. A ratio above 1.0 means the inverter is undersized relative to the array: during peak irradiance, the inverter clips the output to its rated AC limit, sacrificing some generation. A ratio below 1.0 means the inverter is oversized and rarely operates at full capacity.
For UK commercial systems, DC/AC ratios of 1.1 to 1.3 are common because the UK irradiance profile rarely produces sustained full-rated DC output, making some inverter clipping acceptable in exchange for lower inverter costs. The optimal ratio depends on the site's irradiance profile, tariff structure, and export constraints. Electrical survey services confirm the appropriate ratio for each specific installation.