Arizona has the best solar resource in the country — and some of the hardest operating conditions for the equipment collecting it. If your system seems to produce less than the brochure promised, the gap is almost always one of seven things. Here they are, ranked roughly by how often we find them and whether you can do anything about it.
1. Heat — the Arizona tax
Counterintuitively, solar panels lose efficiency as they get hotter. Every panel has a temperature coefficient — typically a fraction of a percent of output lost per degree above 25°C cell temperature — and on a 115°F July afternoon, cell temperatures far exceed that. This is normal and designed-for; what is not normal is anything that makes it worse, like debris packed under the array blocking the airflow that cools it from beneath.
2. Soiling — dust, monsoon residue and droppings
Phoenix dust plus monsoon rain leaves a baked-on film that measurably cuts production, and bird droppings are worse — a hard shadow on one cell drags down its whole string. This is the most fixable item on the list: panel cleaning is included in every SolarCare visit and after every detach & reset we perform.
3. Shading — including the shade that grew after install
Your installer designed around the shade that existed on install day. Trees grow, neighbors build, and rooftop additions — a new AC unit is the classic — cast shadows nobody planned for. Even a sliver of hard shade on one panel can cost far more than its area suggests. If shade has moved in on your array, relocating the affected panels is sometimes worth the math.
4. Orientation and tilt
South-facing at roughly a 30–40 degree tilt is the textbook optimum; west-facing arrays trade a little total output for production later in the day. You generally cannot change your roof — but knowing your orientation explains your production curve, and it matters when panels are reset after a re-roof: they must go back to the engineered layout, not “roughly where they were.”
Talking to us costs nothing
Exact detach & reset quotes are free and same-day from your address, panel count and a roof photo. Diagnostics are $199, full inspections $299 — always quoted in writing before any work.
Get a Free Quote (480) 270-27455. Age and degradation
Panels degrade slowly — typically well under one percent of output per year. That is the schedule. A system down 20% in three years is not “aging”; it has a problem on this list, and finding it is exactly what a $199 diagnostic is for.
6. Wiring, connections and the inverter
Connectors corrode, insulation abrades, and inverters — the hardest-working component in the Arizona heat — fail long before panels do. Electrical faults often show up as a whole string producing nothing while the rest of the array looks fine, which is invisible unless someone (or something) is watching per-circuit production.
7. Birds and what they leave behind
Pigeon colonies hit three items on this list at once: droppings shade the glass, nests block cooling airflow, and debris damages under-panel wiring. If you have birds, fix that first — the pigeon guide covers what it costs you and the bird guard fix that holds.
Know your number
All seven factors show up in one place: your production data. If your monitoring went dark when your installer disappeared, independent monitoring puts real eyes back on the system — because you cannot manage what nobody is measuring.