How Many Peak Sun Hours in Washington? (East vs. West)
Spoke ArticleWashington Dc1 min readVerified Q1 · 2026

How Many Peak Sun Hours in Washington? (East vs. West)

SBI Editorial DeskUpdated Q1 · 20262 sections

When considering solar in Washington, many people immediately think of Seattle's famous cloud cover. However, solar engineers measure viability in "peak sun hours," and Washington actually performs exceptionally well.

01

The Pacific Northwest Solar Reality

Western Washington (Seattle, Tacoma, Olympia) receives an average of 3.5 to 4 peak sun hours per day, while Eastern Washington (Spokane, Tri-Cities) receives a massive 4.5 to 5+ peak sun hours. Modern Tier-1 monocrystalline panels are incredibly efficient and actually conduct electricity better in cooler temperatures. Even through the cloud cover of the Puget Sound, your panels will produce steady, reliable power.

02

Summer Overproduction

Because Washington is so far north, summer days are exceptionally long. Your system will vastly overproduce from May through September, allowing you to bank massive net metering credits to coast through the darker winter months.

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