How Many Solar Panels Do I Need?

What a design should consider

• Annual kWh usage (from your electric bill)
• Panel wattage (higher-wattage panels mean fewer of them)
• Available roof space
• Roof direction
• Shade
• Production estimate for your specific roof
• Utility requirements
• Desired offset (how much of your usage you want to cover)
• Expected future electricity usage

A simple educational example

Say your home uses 10,000 kWh a year. A properly designed system modeled to produce roughly that much annually would be the target — not a random panel count.

So why can't you just divide your annual usage by one panel's wattage and call it a day? Because a panel's rating is its output under ideal lab conditions. Real-world production on your roof depends on orientation, shade, pitch, weather, temperature, and inverter losses. Two 400W panels on two different roofs can produce very different amounts of energy in a year.

Why your neighbor may need more or fewer panels than you

• Different usage — Your neighbor may run an EV, pool, or central AC.
• Different roof — Direction, pitch, and shade change everything.
• Different equipment — Higher-efficiency panels make more energy per panel.
• Different goals — 100% offset versus 80% offset change the design.

What if I'm buying an EV?

Expected future electrical usage can be considered when designing a system — that's one of the reasons we ask about upcoming changes. A new EV can add several thousand kWh a year to your usage. Subject to applicable utility and program rules, a system can be sized to account for that expected load. The right move is to share your driving habits and charging plans so the design reflects them.

What if I'm adding a pool, hot tub, or heat pump?

Same concept. Pumps, heaters, and heat pumps all add meaningful load. If you tell us about planned additions, the design can account for the expected increase in usage rather than just your current bill.