Peak Sun Hours (PSH)

Peak sun hours express a site’s daily solar energy as the equivalent number of hours at full-strength sunshine (1,000 W/m²). A location receiving 5 kWh/m² per day has 5 peak sun hours — even though the sun was up much longer at lower intensity. PSH is the anchor of every honest solar lighting design: a panel’s daily harvest is roughly its wattage × the site’s PSH × system losses, and that must exceed what the LED consumes overnight. Crucially, sizing uses the worst month, not the annual average — a fixture sized on summer sun goes dark in winter. This is why the same solar street light is configured differently for Lagos, Riyadh and Hamburg, and why a supplier who quotes one universal runtime for every market is estimating, not engineering.