How much will solar panels produce in Seattle?

A 8 kWp system facing south at 35° tilt in Seattle produces about 9,727 kWh a year. In a weak year that is 8,131 kWh, in a good one 11,323 kWh — 1,216 kWh per kWp.

That’s about 93% of a typical home’s yearly use (10,500 kWh).

Calculate for my roof

Based on 2014–2023 satellite weather data

Production by month

05001,0001,5002,000JanJanuary: 8 kWp 426 kWh, range 292–561FebFebruary: 8 kWp 500 kWh, range 401–599MarMarch: 8 kWp 850 kWh, range 633–1,066AprApril: 8 kWp 1,001 kWh, range 768–1,234MayMay: 8 kWp 1,082 kWh, range 897–1,268JunJune: 8 kWp 1,072 kWh, range 812–1,333JulJuly: 8 kWp 1,254 kWh, range 969–1,539AugAugust: 8 kWp 1,211 kWh, range 998–1,424SepSeptember: 8 kWp 965 kWh, range 747–1,183OctOctober: 8 kWp 754 kWh, range 542–967NovNovember: 8 kWp 491 kWh, range 314–668DecDecember: 8 kWp 314 kWh, range 231–397

kWh per month

A typical day in July

The sunniest month in Seattle. Output peaks around 12:00 solar time, at about 4.5 kWh in the best hour.

0:006:0012:0018:0023:00 4.5 0

Month by month

Month Weak year, kWh Typical year, kWh Good year, kWh
January 292 426 561
February 401 500 599
March 633 850 1,066
April 768 1,001 1,234
May 897 1,082 1,268
June 812 1,072 1,333
July 969 1,254 1,539
August 998 1,211 1,424
September 747 965 1,183
October 542 754 967
November 314 491 668
December 231 314 397
Year 8,131 9,727 11,323

The months don’t add up exactly to the yearly figure, because each one is the typical value across many years.

Common questions

How much do solar panels produce in winter in Seattle?

From November to February the system produces about 1,732 kWh, which is 17% of the year. The weakest month (December) gives roughly 314 kWh.

Is an east-west roof worth it in Seattle?

An east-west system typically produces 10–25% less per kWp than one facing south, but spreads production more evenly through the day. The exact difference depends on tilt and shading.

Compare an east-west roof for Seattle

Ground mount or roof in Seattle?

A ground mount can be tilted and aimed freely, which can add some yield, but it costs more and needs space. Compare both for your own plot.

Check a ground-mounted system in Seattle

Your roof is not an average roof

Set your own tilt, direction, shading and inverter limit and get a range for your address.

Calculate for my roof

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Climate data: Photovoltaic Geographical Information System (PVGIS) — European Commission, Joint Research Centre