Solar panels can generate large amounts of electricity during the year. For example, a 10-kilowatt system produces well over 15,000 kWh per year with favorable sunlight conditions.
Since central air conditioners have the highest energy consumption in most homes and commercial buildings, it makes sense to ask the question: “Can my air conditioner run with solar power?” The short answer is yes, but there are some technical details to consider.
First, we must keep in mind that solar panels have a variable output that depends on sunlight. They are most productive around noon, but their output is lower in the early morning and late afternoon when there is less sunlight. Solar panels also become much less productive with cloudy weather, and their output drops to zero at night.
Air conditioners depend on a refrigerant compressor to achieve their cooling effect, and this device needs a constant and stable power supply. Since solar panels have a variable output, using them to power an air conditioner directly is not possible. However, there are two viable solutions for this problem:
- Using a grid-tied solar system to power your air conditioner. When sunlight is abundant, your solar panels will probably generate more power than what your air conditioner needs. Surplus production can be used by other home devices or sent to the grid in exchange for a power bill credit. When sunlight is low or unavailable, your air conditioner simply runs with power from the grid.
- Using a solar battery system to power your air conditioner. When solar panels are combined with a battery system, the output is no longer variable because the battery can be used at any time (as long as it has charge). Solar battery systems can be designed to be grid-connected or off-grid, and each option has pros and cons.
Some air conditioner manufacturers now offer systems with built-in solar panels, but generally they are not designed to run off-grid. These solar panels cover a fraction of the AC unit consumption, making it more efficient, but the grid is still the main power supply.
If you want to use solar power as the main input for an air conditioner, you need a larger photovoltaic system: with just a few panels, you will only cover a small portion of the cooling load.
Powering Your Air Conditioner with Grid-Tied Solar Panels
When you want to reduce your power bills with solar panels, the idea of remaining connected to the grid can sound counterintuitive. However, this configuration has many advantages:
- If there are many cloudy days in a row and your solar panels are unproductive, the grid can be used as a backup power supply. If you go off-grid, you need to purchase a diesel generator with enough capacity for these emergencies.
- If there is a day where your consumption was higher than usual, exceeding the capacity of your solar panels, the grid is available to supply the missing kilowatt-hours.
Air conditioners in particular need a very stable power supply to operate properly, and their electronic components are susceptible to sudden voltage changes. By remaining connected to the grid, you can ensure a constant power supply for indoor cooling.
If the output of your solar panels drops suddenly because a passing cloud has blocked the sun, your air conditioner can switch to grid power, and you will not even notice.
Another advantage of grid-tied solar panels is being able to use their electricity for other devices, saving on power bills all year long. This is especially helpful during the cooler months, when you’re no longer using the air conditioner.
On the other hand, if your solar panels are used exclusively for air conditioning, you only save during the warmer months and their power is wasted the rest of the year.
Combining an air conditioner with grid-tied solar panels is also very convenient. You don’t need specialized products, and you can simply use what is available in the market from established brands.
If you have technical issues with either of the two systems, you can simply contact the solar installer or AC provider as needed.
Powering Your Air Conditioner with a Solar Battery System
A conventional solar panel system can reduce your air conditioning costs during the day. However, you do need energy storage if you intend to use solar power at night and during cloudy days. You also need more solar panels, since they must now accomplish two things:
- Providing enough electricity to meet your daytime consumption, including air conditioning.
- Charging your battery system to meet your nighttime consumption.
Solar batteries offer more flexibility than traditional systems with only solar panels. You can size the solar panel kilowatts and battery kilowatt-hours optimally, according to the energy needs of your home.
A solar energy storage battery can also be designed for off-grid operation in case you live in a remote place with limited grid coverage, or you simply want to go off-grid as a lifestyle choice.
To power an air conditioner with a solar battery, there are two important requirements:
- The solar battery system must be able to sustain a high enough power output to keep the air conditioner running.
- The system must have enough storage capacity to keep the AC on during the hours when there is no sunlight available for recharging.
The cost of setting up this system is lower if your air conditioner is as efficient as possible. You should look for a unit with the ENERGY STAR label, and keep in mind that split systems are more efficient than window-type or packaged terminal air conditioners (PTAC). Look for an air conditioner with the highest possible energy efficiency ratio, and you will need fewer solar panels to cover its electricity consumption.
As mentioned above, solar batteries can be designed to remain connected to the grid, or you can decide to take your home off-grid. Each option requires a different approach, and there are advantages and disadvantages in each case.
The main benefit of staying connected to the grid is using it as a backup power supply when your solar panels cannot generate enough electricity. For example, this can happen if there are many consecutive days with bad weather.
Instead of burning many gallons of expensive diesel with a generator, you can switch back to the grid temporarily. Staying connected is also helpful if you’re using other high-power devices along with your air conditioner, which can exceed the capacity of an off-grid solar battery.
Going off-grid gives you full energy independence, but you must be prepared for a higher investment, especially if you intend to run an air conditioner with solar panels.
- Since you don’t have the grid connection as backup, your solar battery system must be sized according to the highest possible consumption you can expect. This means having a larger and more expensive system.
- You will also need a diesel generator or another backup generation system that doesn’t depend on sunlight in case you have several cloudy days in a row.
Also, keep in mind you cannot go off-grid with a traditional solar inverter. In this case, you need a more powerful device called a multi-mode inverter which is capable of running air conditioners and other high-consumption devices with no help from the grid.
Since you’re going off-grid, your solar battery system must be designed to keep all devices running, not only the air conditioner.
Solar Powered Heat Pumps: Renewable Cooling and Heating
Most homes and commercial buildings use electricity to power their air conditioners, while space heating systems use natural gas or other fossil fuels. However, by combining solar panels with a high-efficiency heat pump, your building can use solar power for both heating and cooling. Heat pumps are based on the same technology as air conditioners, but the system configuration is reversed to achieve a heating effect.
Some heat pump models can only provide heating, but others have a reversible design and can be used as air conditioners during summer. This means you can use a single device for your heating and cooling needs, instead of having a separate air conditioner and furnace. Also, since a heat pump runs with electricity, it can take advantage of solar power all year long.
The recommendations given above for solar power air conditioning also apply here. You should look for the most efficient heat pump available, ideally an ENERGY STAR unit, since this will let you cover its consumption with less solar panels. Also, staying connected to the grid lets you use a smaller solar battery system, since you can always switch to grid power as backup.
There are two main types of heat pumps, and both operate with electricity. Air-source heat pumps or ASHPs normally consume 2-4 times less power than a resistance heater, while geothermal or ground-source heat pumps (GHSP) consume 4-6 times less power, making them the most efficient technology available.
Solar Powered Air Conditioning: Typical Costs of the Main System Components
Giving a cost estimate for a solar-powered air conditioning system is difficult, since the energy consumption profile and cooling needs change a lot from home to home. However, the following are some typical costs of system components:
- Solar panels have an average installed cost of around $3,060 per kilowatt in the US, without including energy storage. This means a 5-kW system will cost around $15,300, while a 10-kW system will cost around $30,600. However, actual costs are lower thanks to the 26% federal tax credit, and there may be additional incentives in your location.
- A home energy storage battery will normally cost around $10,000 – $15,000. Keep in mind that larger homes may need two or more units.
The cost of an air conditioning system is more variable since it depends on both tonnage and rated efficiency. For example, you might pay less than $5,000 for a central AC unit that meets the minimum efficiency standards, or more than $10,000 when using top efficiency equipment. However, energy efficiency will pay off in the long run, and it also means you would need fewer solar panels to offset your cooling costs.