Eastern Washington is a different solar climate
The Cascades divide Washington into two climates, and Spokane sits firmly on the sunnier side. A given array produces meaningfully more here than the same array on a Seattle roof.
That matters when reading a quote, because a production estimate built on a statewide assumption will understate a Spokane roof. That is an unusual direction for a quote error and it makes a good project look mediocre.
Ask what data source the annual production estimate used and whether it applies location-specific irradiance for your address rather than a state or regional average. Ask for the figure in kilowatt hours per year rather than only in dollars.
Ask also how the model handles winter. Spokane gets real snow, and snow cover is a genuine if temporary production loss that a careful estimate accounts for and a generic one does not.
The Avista rate trajectory
Avista has proposed increasing rates by about 14 percent next year and roughly 25 percent by 2030. Proposals are not final orders, and a regulator may approve less, but the direction is established.
For a solar decision that direction is the substance. The system is bought once at today prices and displaces electricity bought at tomorrow prices for twenty-five years.
Ask what escalation rate the savings projection applied and whether it was based on the utility own filings or on a generic national assumption. Those produce very different answers over a long horizon.
And ask to see the projection at zero escalation as well. If the case holds without any rate increase at all, it is a robust case; if it only works at an aggressive escalator, you have learned what the quote is actually resting on.
More production makes the April rule sharper
Washington credits excess generation at the retail rate under RCW 80.60, but on April 30 each year any unused credit from the previous year is granted to the utility with no compensation.
A sunnier location makes it easier to build a system that overshoots annual consumption, which means the forfeit rule is a more live risk in Spokane than in Seattle. The better the resource, the more careful the sizing has to be.
So resist sizing to the roof simply because the roof performs well. Ask what percentage of annual usage the design covers and require a specific justification for capacity beyond it.
In a climate with cold winters, a planned heat pump is a particularly credible reason to size ahead, because it genuinely raises future consumption. A general expectation of using more power is not.
Rebuilding the Washington arithmetic
The 30 percent federal Residential Clean Energy Credit under Section 25D expired for property placed in service after December 31, 2025, so a cash or loan purchase in Spokane receives no federal tax credit. Section 48E survives at 30 percent for third-party owners under leases and power purchase agreements.
Washington has no state income tax and no state solar credit, so nothing at state level replaced it.
What exists is the sales and use tax exemption under RCW 82.08.962 covering equipment and installation labour on systems up to 100 kW AC through December 31, 2029, and retail-rate net metering with the April 30 forfeit.
Then add the electricity you stop buying, at your actual Avista rate, with the escalation assumption stated and sourced. Ask for the version at zero escalation alongside it.