Solar has been common in the Valley long enough that a body of folk wisdom has grown up around it. Some of it is harmless. A few pieces quietly cost homeowners production year after year. Here are the ones that come up most on Arizona roofs, and what is actually going on.
Myth: Rain Keeps Your Panels Clean Enough
This one sounds reasonable and fails on two counts. First, Phoenix simply does not get enough rain to matter. An array can go an entire season without a single soaking, and a light sprinkle does almost nothing except turn dry dust into a thin mud film that dries right back onto the glass.
Second, rain that does fall picks up dust on the way down and leaves minerals behind as it evaporates. That is the same reason your car looks worse after a light shower than before it.
Rain is not a cleaning. It is a rinse that leaves the dirt in place and the minerals behind.
Monsoon storms are the clearest example. They blow a tremendous load of fine dust into the air and then drop rain through it, which is close to the worst possible combination for a panel surface.
Myth: The Loss Is Too Small to Be Worth Fixing
The reasoning usually goes that a little dust cannot block much light, so why bother. But a soiling film is not like a leaf sitting on one corner. It covers the entire surface fairly evenly, which means every cell in the array is working through the same haze at the same time. There is no clean section making up for a dirty one.
The cost side is easy to underrate too. Missing production is not a one-time loss, it is a small deduction repeated every sunny hour for months until someone washes the glass. Arizona gives you an enormous number of those hours, which is the whole reason solar pays here.
Myth: All Panels Need the Same Maintenance
Two arrays a mile apart can have completely different needs. What actually differs:
- Tilt. Low-slope roofs hold dust. Steeper arrays shed some of it on their own.
- Surroundings. A house backing onto open desert or a dirt road collects far more than one in the middle of a fully landscaped subdivision.
- Trees. Pollen and fine litter stick to glass differently than mineral dust does, and overhanging limbs invite birds.
- Wildlife. An array with birds nesting under it needs a different plan entirely, because cleaning without proofing just resets a clock.
- Height and access. A two-story tile roof changes the safety equipment involved, which is worth knowing before anyone suggests you handle it yourself.
Myth: A Hose and Some Dish Soap Will Do It
This is the myth most likely to cause actual damage. Three problems come with the DIY version.
Soap leaves a residue film, and residue is a magnet for the next round of dust. Tap water in the Valley is hard, so spraying and letting it dry bakes mineral spots directly onto the glass. And spraying cold water across panels that have been sitting in full afternoon sun puts real thermal stress on hot glass.
There is also the part nobody mentions until it goes wrong: you are standing on a hot roof, next to energized electrical equipment, holding a hose. Two Bits Solar Cleaning uses deionized water for exactly these reasons. Pure water lifts dust without any soap at all and evaporates leaving nothing behind, which is also why the runoff reaching your landscaping is just water and the dust that was already on your roof.
If you are unsure which of these applies to your system, our frequently asked questions covers the common cases, and you can always get a quote if you would rather have someone look at it directly.