The year 2023 is on track to become the hottest ever recorded on Earth. Air conditioning can provide relief from the heat. But if too many people rely on it, the electric grid can’t keep up, forcing power companies to temporarily cut service to millions of households.
Solar air conditioners offer a straightforward solution to this dilemma.
Where I live on the coast of Central California, heat is seldom as oppressive as in Southern California, Arizona, Texas or the Southeast. Seldom doesn’t mean never, though. So as part of the solar upgrade to our off-grid property, we’re looking closely at air conditioning options.
We’re leaning heavily in favor of a heat pump system, because it cools as well as heats, and our solar array should handle it quite nicely. But it turns out there are other ways we could go.
One example: Australia’s Commonwealth Scientific and Industrial Research Organization (CSIRO) is developing a rooftop system that uses the sun’s energy to heat water, which vaporizes and passes through a spinning desiccant wheel to dry out. It then goes through an evaporative cooler and finally into a duct system to cool the house.
The system provides hot water and cool air for the house while using only enough electricity to spin the desiccant wheel and circulation fans. It isn’t a realistic option for us, but it might be for other homeowners.
How Does a Solar-Powered Air Conditioner Work?
The most common solar air conditioner design uses photovoltaic (PV) panels to power the compressor and fan. The compressor may connect to indoor evaporative units (think mini-splits) or circulate cool air through a duct system. It draws all its power from the panels, although hybrid units are available that can also use grid power.
In places where grid power isn’t available, a battery can be added allow the air conditioner to operate at night.
Another type, called a solar thermal air conditioner, uses water heated by the sun to drive the refrigerant. Like a compressor, the hot water condenses a refrigerant and drives it into evaporator coils, vaporizing it and absorbing heat from the house.
This type of unit needs some electricity to operate circulation fans, but not as much as a conventional air conditioner, and it works with smaller panels.
Types of Solar-Powered Air Conditioners
PV-powered air conditioners come in three types: DC current, AC current, and hybrids that can run on both types of power.
DC units: Solar panels output DC power. So if the air conditioner fan and compressor have DC motors, they can use that power directly. Such units typically operate at 12, 24 or 48 volts.
AC units: These utilize the 120-volt AC signal from the power grid. They can operate directly from a solar panel, but the panel signal has to first pass through an inverter, which reduces efficiency.
Hybrid units: These use DC and AC signals. They can draw directly from the panels when the sun is out, and from the power grid when it’s not.
Mini-split systems are quite common. They feature an outdoor compressor unit and one or more indoor units containing evaporative coils and a circulation fan. The panels are usually mounted near the compressor. Wires bundled with the refrigeration tubing carry electricity to the indoor units.
Window-mount units are also available. They usually come with a panel array that mounts on the roof or the side of the house.
Solar-Powered Air Conditioner Pros and Cons
Solar air conditioning offers a solution to the nagging problem of power grid overload during hot weather, but only if enough homeowners go for it.
To make the decision easier, the federal government offers a 30 percent solar tax credit towards the purchase and installation of new solar equipment. That’s a big incentive. Here are others:
You’ll stay cool even if there’s a grid overload and a blackout.
You can tie your air conditioner into your existing PV system and save on materials costs.
You’ll save money on your energy bill.
Your air conditioning system works best when you need it most — when the sun is out.
The main drawback? It won’t work if there isn’t enough sun. That’s a problem for people on shaded properties or in the wrong climate zone. Other drawbacks include:
Your air conditioner won’t work at night unless it’s tied to the grid or you purchase a battery pack.
Solar air conditioners cost more than conventional ones. The average cost to purchase and install one is around $3,400, though tax incentives reduce that by 30 percent.
Your air conditioner might not work during prolonged period of cloudy or rainy weather, even if you have a battery pack.
Solar panels don’t last forever. Their average life expectancy is around 30 years, but that can be shortened by severe weather or salty, corrosive air.
What’s the Bottom Line?
If your property gets enough sun, a solar air conditioner is a wise investment that will reduce your energy bill and probably increase your property value as well. You’ll also be doing your part to keep the electric grid up and running.