Solar Installers: Summer Heat Cuts Panel Output, Not Efficiency
Most homeowners assume peak summer sun means peak solar production, but it's actually the opposite. Photovoltaic panels lose 0.5% efficiency for every degree Celsius above 77°F, so a 95-degree June day cuts real output by 8-10% compared to a mild spring morning. This matters when you're evaluating a solar installer's production estimates.
Before signing, ask your installer for performance projections by month, not just annual totals. Request their thermal derating factor in the contract. Then cross-check their summer figures against actual data from similar systems in your area using PVWatts (a free NREL tool). A contractor padding summer numbers to hit annual targets is either inexperienced or counting on your inattention. Also verify whether your inverter has active cooling; cheaper models throttle output on hot days.
Get this detail nailed down now, before the contract is final. Summer performance directly affects your payback timeline and return on investment, yet many installers gloss over it until you're already locked in.