What matters most
Use interval consumption where available. High summer air-conditioning use may align with solar output, but evening peaks and tariff design can still materially change the result.
Utility rules drive the calculation
APS, SRP, TEP, cooperatives, and municipal utilities use different rate structures and export-credit rules. Confirm the applicable tariff, time periods, fixed charges, export value, and any demand component in writing.
System sizing should follow household load and tariff economics rather than simply filling every available roof surface.
Check incentives and tax treatment
Federal, state, and local incentives may be available, but eligibility and value can change. Confirm the current programme rules, tax liability requirements, equipment qualifications, and application timing before including any incentive in the purchase decision.
Test your assumptions
Use your current electricity rate and a cash quote to create a baseline before comparing finance offers.
Open the calculator →Questions to ask before signing
- Which utility tariff and export rate are used in the model?
- Does the plan include time-of-use or demand charges?
- How are summer cooling loads represented?
- Which incentives are assumed, and who verifies eligibility?
- For batteries, what is the operating strategy and backed-up load?
Methodology and primary sources
Primary references include the Arizona Corporation Commission, serving-utility tariffs, US EIA electricity data, NREL PVWatts, and DSIRE. Dated rate and incentive claims are verified before publication.