Homeowners in deserts invest a lot in solar installations to reduce their electricity bills, just to realize that the energy generated is minimized due to accumulated dust, and the heat generated by the roof that’s not properly insulated or ventilated. Clean, intact ducts, attics insulated to current standards, and other measures are going to have a greater impact than the next gadget or add-on to your solar system.
Your air conditioner is the real villain
Before deciding to invest in a solar array to reduce your electricity bill, consider the big picture and the most effective way to reduce your energy expenses. In many cases, especially in hot regions, air conditioning is the main electricity eater in most households. If you have an old, underperforming unit and/or a leaky duct system, investing first in a new A/C unit and making some duct improvements will probably reduce your electricity bill more than investing in a solar array.
Heat is quietly sabotaging your solar output
Many people are surprised to learn that the hotter it gets, the worse solar panels perform. Solar panels have a negative temperature coefficient – specifically, -0.4 percent to -0.5 percent for every degree Celsius above the 25°C standard during lab testing. Panel surface temperatures can exceed 65°C on a July afternoon, translating to 15 to 20 percent production losses, exactly when you need your air conditioner running the most.
This is the ironic challenge of solar in arid regions. The sun is strong, but high temperatures reduce panel output. Tilt angle and racking height matter as well. Low, flat panels often seen in deserts block heat from escaping and limit cooling airflow. Raising the racking and providing some clearance to facilitate airflow can cool the panels and help capture more of the sunlight.
Dust doesn’t wash itself away
In wetter regions, rain often solves the soiling problem for you; storms will wash dirt and grime off the face of the panels every few weeks or so, and voilà! Panels are re-sparkling, free of charge. In truly arid regions, however, that natural benefit never arrives. Plenty of U.S. solar farms go six months or longer without meaningful rainfall. So, just as in the rest of your house, rain doesn’t actually clean off accumulated dust; every windy day, or even just every day, adds some more to the pile.
The problem is bigger than most homeowners would think. An oft-cited 2018 NREL study calculated that accumulated dust and grime can reduce solar output by 25 to 30 percent in the same kind of dry, low-rainfall regions that are precluded from regular natural cleaning. This isn’t a rounding error. This is a solid quarter of the energy your system could produce annually, just gone, because nobody’s washed the windows since spring.
Birds turn shade-seeking into a maintenance nightmare
Extreme heat conditions in the desert are tough on your equipment. They’re even tougher on wildlife, driving animals to seek shelter in whatever shade they can find and underneath the solar panels on your racks is a nearly perfect place for a small animal or bird to rest, while the panel above screens it from the direct sun and it’s raised off the burning ground below. What starts as a shady escape for an animal in the gap under a raised solar panel can quickly become a nesting site and that poses obvious problems and expenses for your operation.
The first is what comes out: bird guano. It’s acidic, and, if left sitting directly on the panels or the wiring, it can etch surfaces and begin to create resource-draining, localized hot areas on the cells directly under the build-up of concentrated waste. Each grain-size layer of the hot spot keeps light from a section of the cell beneath it, but the rest of the panel is still pumping in electrical current that can become dangerous thermal overload in spots. In other words, the panel can fry that section of the solar panel faster than the design intended.
The other problem is the debris from nesting itself: twigs, sticks, and dry leaves, as well as the birds’ own feathers. This junk starts to accumulate under the array and blocks air flow – and you need that airflow to keep the panels cool. If the panels are already searing hot due to temperature and orientation, you can’t afford to let an insulating layer of bird flotsam block precious cooling underneath, where the cell is already too hot.
Most warranties exclude damage caused by nesting birds, their droppings, or their nests getting in the way of the operation of the panels in the desert heat. It’s not until you try to lodge a warranty claim over damaged cells or wiring due to a bird’s nest that you find out your claim will be rejected and you’ll be paying for the repairs yourself. Bird proofing solar panels with mesh guards, edge clamps, or spike deterrents keeps birds out from day one. These systems simply and inexpensively exclude birds from the roof or array without harming the environment and are typically integrated right into the racking systems for new installations.
Cleaning panels without wasting water
After birds have been shooed away and debris has been cleared, you still have the ever-present dust issue. This is the bottleneck for desert owners: water is scarce. You can’t wash your solar panels like a driveway, sending rivers of water down the slope and hoping for the best. Both your local water restrictions and your own conservation ethic say you shouldn’t.
The best techniques use virtually no water. Dry-brushing with soft, non-scratch tools will remove light dust with no water but it’s virtually impossible to use after a good caking from a muddy rain. Scrubbing gently with squeegee-style tools that wet the panel with de-ionized water before wiping it nearly dry can leave your panels looking nearly new. That’s not a practical job for most homeowners, however. Your best bet will be employing a pro low-water service specifically tailored for arid environments. These companies focus on using as little water as possible and often perform an inspection which will uncover a loose connection, early corrosion, or a few twigs under the panel before they wear a hole in your sheet.
Attack heat gain at the building level too
Proper maintenance of your solar panels is only half the battle. The other half is taking care of your home, because the same heat that degrades your solar output is also increasing your cooling costs.
For most single-story homes, especially in the desert, the primary line of defense against that heat is attic insulation. An under-insulated attic essentially transforms into an oven that blasts heat down into your living space all day and night, pushing your air conditioner to work harder. Radiant barriers, a reflective sheeting placed under the roofline, help bounce out a good portion of that solar heat before it has a chance to get absorbed into your attic. Cool roof coatings work in a similar way from the outside by reflecting sunlight instead of absorbing it, which in turn reduces the temperature on your roof and the amount of heat that enters your home.
Add one or both of those upgrades to your solar maintenance and you’ll start reaping greater benefits, as they’re both essentially fighting the same battle: unwanted heat. A clean, well-functioning solar system combined with a well-insulated reflective roof will produce more power and also demand less of it.
Get an energy audit before spending on anything big
It can be easy to take a stab at where you’re wasting money on energy. But a pro energy audit, often paired with a blower door test, eliminates the need to play around. This test pressurizes or depressurizes your home just a little bit and then measures airflow to find exactly where that precious conditioned air is making a run for it: whether it’s gaps around windows, unsealed attic access panels, or leaky ducts running through an unconditioned attic.
Speaking of which, duct sealing is one of the most overlooked solutions in desert homes. If you have ducts in a 150°F attic, even a small gap or a disconnect joint will have your cooled air going to waste faster than you’d like. Fixing those leaks will often cost a fraction of what a new AC is going to, all while getting those cooling bills lower without even having to touch the gear. And an audit will tell you whether you should be focusing on ducts, insulation, or your compressor, rather than just throwing money at all three.
Choose cooling equipment that fits dry air
Not all cooling methods work equally well in all locations, and this causes a lot of homeowners in dry areas to spend more than they need to. Evaporative coolers, or swamp coolers, function by drawing arid air through water-soaked pads. They’re far cheaper to operate than refrigeration-style A/C systems because they take advantage of low humidity. In truly dry climates, the efficiency advantage isn’t trivial, it’s often more than a 50% reduction in cooling costs.
Evaporative cooling isn’t the best choice everywhere, though. In the milder, slightly more humid parts of the same general region an hour or two away, a high-SEER heat pump is probably the better call since evaporative systems lose steam as humidity increases. Needless to say, it’s worth taking the time to match your cooling method to your local conditions, rather than defaulting to what everyone else seems to be using.
No matter what system you ultimately go with, a smart thermostat can wring even more savings out of it. Set-back scheduling that lets the house get a touch warmer during peak afternoon heat, then cools it off in time for everyone to return, will slice real dollars off those peak-load hours with barely a change in home satisfaction.
Build a seasonal maintenance calendar
There is no single solution to any of this. Heat, dust, and birds are inevitable, seasonal problems. The fixes must be seasonal too. Spring is the time to birdproof and get your panels full-on scrubbed, but before you do that, so that you’re not disturbing new hatchlings, consider a slight lift of the panel to give breather room for excessive heat to escape during the summer. Early summer, before your AC is in constant use, is the best time to change your filters, check refrigerant levels, and get your ducts tested for leaks. Before the monsoons hit, you’ll need to check the penetrations where your panels attach to your roof and the flashing. Wind-whipped debris can loosen fasteners guaranteed to already be screaming hot.
Homeowners who treat this as a calendar item, not a someday task, consistently get more out of both their solar investment and their cooling equipment. The maintenance is cheap. The alternative – replacing degraded panels or a burnt-out compressor – is not.
