Sun hours are not the same as output
Panel efficiency falls as cell temperature rises. In a climate like Yuma's that is not a marginal effect, and a production estimate that does not account for it will overstate what your roof delivers in exactly the months you need it most.
Ask what temperature assumptions sit behind your estimate, whether the model was run for your specific location and roof rather than a regional average, and ask to see monthly figures rather than an annual total. The annual number hides the shape.
Ask about mounting too. Airflow beneath the modules affects operating temperature, so how the array is mounted has a real effect on hot-weather output, particularly on a low-slope or tightly flush installation.
None of this argues against solar in Yuma. The sun resource here is genuinely exceptional. It argues for a production estimate that reflects the climate honestly, so that what you are comparing between installers is engineering rather than optimism.
Your cooling load is the best possible use of production
Exported solar in Arizona is credited below the retail rate under net billing export rate riders, so electricity you consume as it is generated is worth more than electricity you export. That makes the timing of your consumption central to the arithmetic.
Yuma households are fortunate here. Air conditioning runs hardest through the afternoon, which is when the array is producing, so a large share of production is consumed on site rather than exported. That alignment is the strongest part of the case for solar in this city.
Ask your installer to model the self-consumed share explicitly for your household rather than quoting an annual offset percentage. Two homes with identical arrays and different occupancy patterns get very different results, and the model should reflect yours.
Small changes help further and cost nothing. Pre-cooling the house in the early afternoon while production is strong, and running laundry and dishwashing in daylight, shifts consumption into the production window without buying anything.
Sizing, and the roof it all sits on
Size to what your household actually uses during daylight rather than to your annual total, since the surplus is credited below retail. Ask for models at two or three sizes with the self-consumed share shown for each, and look for the point where the return stops improving with size.
Confirm which utility serves your address and what its export arrangement is before any of that, because the export rate is the number the whole calculation turns on. Ask the utility directly and get it in writing rather than taking it from a quote.
Check the roof covering before anything is ordered. Panels outlast most coverings, and intense sun and extreme heat age roofing faster than a year count suggests, so ask for a condition assessment rather than an age estimate. Replacing a covering that is near the end of its life before the array goes on avoids paying to remove and reinstall it later.
Ask how mounting penetrations are flashed and sealed, what the roofing manufacturer approves for your covering type, and what the workmanship warranty covers on them and for how long. Leaks around mounting hardware are the most common physical failure in residential solar.
The state credit you claim yourself, and the federal one that ended
Arizona still has a state income tax credit of its own, claimed on Arizona Form 310, Credit for Solar Energy Devices. It is calculated by multiplying the cost of a solar energy device by 25 percent, capped at $1,000, and the form provides for tracking credit carryover across multiple years.
Ask a tax advisor how the cap and the carryover apply to your situation before you rely on a figure in a quote. A credit is only worth what you can actually use against tax owed, and an installer is not the right party to advise you on that.
Arizona also exempts solar equipment from state sales tax and excludes it from property tax, so the improvement does not raise your property tax bill the way a renovation of similar cost would. Neither arrives as a cheque, which is exactly why they get left out of people's own arithmetic.
The federal position has changed and much published material has not caught up. The 30 percent Residential Clean Energy Credit under Section 25D expired for property placed in service after December 31, 2025, so a cash or loan purchase now does not receive it. Section 48E survives at 30 percent for third-party owners under leases and power purchase agreements, so such a provider may claim it and reflect part of the value in the rate offered. Ask what they claim and what actually reaches you, and confirm with a tax advisor.