How many solar panels do I need?

There is no meaningful average, because the answer depends almost entirely on how much electricity you use and how much sun your roof receives. A household using 900 kWh per month in a sunny location needs a much smaller array than one using 2,000 kWh in a shaded one. Anyone quoting you a panel count without first looking at your usage history and your roof is guessing.

Size the system to your annual electricity consumption first, then adjust for what your roof can actually hold. Annual usage in kilowatt-hours is the starting number; divide it by your location's expected production per kilowatt of installed capacity, and you get a rough system size. Then confirm the roof has enough usable, unshaded area to fit it.

Your utility bill usually shows monthly kilowatt-hour usage, and your utility's online account typically provides 12 months of history for download. Twelve months matters more than one, because a single summer or winter month can be misleading. If you have recently added an EV charger, a pool, or a heat pump, adjust upward — the last year of history may not reflect your next year of usage.

Often, yes. The usable roof area — after accounting for setbacks, vents, chimneys and shading — frequently constrains the system before your budget or your usage does. Higher-efficiency panels produce more power per square foot, which can matter a great deal if your roof area is limited.

Residential panels are commonly around 3.5 feet by 5.5 feet, so roughly 17 to 20 square feet each. But panels need spacing and cannot occupy every square foot — obstructions, fire setbacks and access paths all take up area. A practical planning figure is that usable roof space is meaningfully less than the total roof area.

Usually, but not always. Covering your full annual consumption is a common target, though it depends on how your utility credits excess production and whether your roof can physically fit the array. Oversizing beyond what your utility will credit is generally not economical, and undersizing may leave you buying more from the grid than necessary.

Substantially, and this is one of the most common sizing mistakes. An EV charger or a heat pump can add thousands of kilowatt-hours per year to your consumption. If you are planning either within the next few years, size for the future usage rather than your current history — retrofitting a larger array later costs more than doing it once.

Orientation, pitch and shade all matter. South-facing roofs at moderate pitch produce the most in most US locations; east and west orientations produce less but can still work well. Shade from trees or nearby buildings reduces output, and its impact depends on when during the day it falls. A proper production estimate models all three rather than assuming an ideal roof.