How many solar panels do I need for my house in Oregon?

Divide your yearly electricity use by what one kW of solar produces where you live. In Oregon that ranges from about 1,100 kWh per kW on the coast to about 1,600 kWh per kW in Central and Southern Oregon. A home using 11,000 kWh a year typically needs 7 to 10 kW, or about 16 to 23 panels at 440 watts.

How is this calculator different from a quote?

It uses county-average sun and your utility's average rate. A quote uses your exact roof direction, tilt, shading and 12 months of usage, which can move the result by 10 to 20 percent either way.

How much roof space do solar panels need?

A modern 440-watt panel is about 21 square feet. Allow extra space for fire-code setbacks from ridges and edges, so a 20-panel system usually needs about 450 to 550 square feet of usable, unshaded roof.

Should I size solar to cover 100% of my bill?

Usually close to it. Oregon net metering credits summer surplus against winter use, but utilities cap credit carryover annually and fixed monthly charges remain. Many homeowners size for 80 to 100 percent of annual use, and more if they plan to add an EV or heat pump.

Solar calculator

How many solar panels do you need?

Estimate system size, panel count and savings for your Oregon home in under a minute.

Aerial view of a modern Oregon home with a fully paneled solar roof.

Estimated yearly use: 11,718 kWh
System size to offset it: 7.2 kW
Panels (440 W): 17
Roof space, approx.: 357 sq ft

A system this size would offset about $1,992 of Pacific Power energy charges in year one. Fixed monthly charges stay on the bill.

Assumes a south-facing roof, 80% system performance and current average utility rates. For city-level production modeled by NREL, see our Oregon service area pages, and for rate history, the Oregon electricity rate map.

The math

How the estimate works

Your bill minus the utility's fixed charge, divided by its energy rate, gives your monthly kWh.
Your county's peak sun hours times 365 days times an 80% performance factor gives yearly kWh per installed kW.
Yearly use divided by kWh per kW gives the system size; dividing by 440 watts gives the panel count.

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