Open circuit voltage (OCV) is the maximum voltage a photovoltaic module produces when no load is connected and no current flows. Typical residential solar modules have OCV ratings between 37-42V, with this value increasing in cold temperatures and decreasing in heat.
Technical Specifications
OCV is measured with a multimeter under standard test conditions (STC) of 1000 W/m² irradiance and 25°C cell temperature. The temperature coefficient for OCV averages -0.3%/°C, meaning cold weather can increase voltage significantly. A 40V module in -10°C conditions may reach 43.2V OCV. System designers must account for this rise when sizing DC circuits per NEC 690.7(A), which requires adding 25% to the maximum OCV for proper breaker and conductor selection.
Practical Significance
OCV establishes the upper voltage limit for module strings. Ten modules at 42V maximum OCV in winter create 420V, approaching typical inverter limits. Exceeding the inverter’s maximum input voltage causes equipment shutdown and potential damage. Accurate OCV calculations ensure safe system design across all climate conditions and seasons.