Definition: Peak sun hours occur when solar irradiance averages 1,000 watts per square meter, typically around midday when the sun is at its strongest. Solar Generation: During these hours, solar panels operate at maximum efficiency, generating the most electricity. Moreover, you can also play around with our Solar Panel Daily kWh Production Calculator as well as check out the Solar Panel kWh Per Day Generation Chart (daily kWh production at 4, 5, and 6 peak sun hours for the smallest 10W solar panel to the big 20 kW solar system). Now, the amount of. The term peak makes its way into many solar panel explanations. electric power sector totaled about 4,260 billion kilowatthours (BkWh) in 2025. In our latest Short-Term Energy Outlook (STEO), we expect U. 6% in 2027, when it reaches an annual total of 4,423 BkWh.