I finally broke down and turned on the heat in my home as temperatures approached freezing last night in Southwest Florida. About a month from now, when electric bills start coming in unexpectedly high, Florida Solar Design Group will start getting phone calls about solar panels for space heating in homes. I’ll get out ahead of things and answer some questions now.

Can I use solar panels to heat my house?

First, it is important to note that there is a distinct difference between solar thermal panels and solar electric panels. Solar thermal panels heat fluids (including gases like air) either directly or through a heat exchanger. Solar electric panels convert solar radiation into electricity. They are very different technologies. Now that we have that covered…

Can I use solar thermal panels to heat my house?

You are essentially heating your home with solar thermal energy every day. As solar radiation hits your roof, walls, and windows, the heat generated is transferred to the air in your home. Of course, this can be a slow and inefficient process. If it’s not enough, there are ways to make this process more effective. For example, you could absorb heat using purpose-built solar thermal panels, absorbing more of the sun’s energy, and then do something to better transfer that heat into the air inside your home. This would involve an active system, pumping fluid through an under-flooring heat exchanger or some other system that blows air over a heat exchange coil into your home. The problem with this is that it isn’t very efficient. There are moving parts involved, and the components would be expensive. You wouldn’t get great heating performance, and more importantly, the heat may not be available exactly when you need/want it.

There are other practical reasons that existing solar thermal space heating systems are not popular in Florida. Proper installation requires that return air ducts be on the floor or low to the ground. You want the heat provided to enter the room near the floor, not the ceiling.  Since basements and crawl spaces are rare, it is almost impossible to retrofit homes with the required ducts. Under-floor radiant heating tubes can be installed, but that gets us to the next issue, which is that solar space heating only works when the sun is out, and in Florida we really need heating primarily at night when the coldest temperatures are experienced.

Can I use solar electric (photovoltaic) panels to heat my house?

There is no direct way to use solar electric panels to heat a home. As I mentioned earlier, solar electric panels generate electricity. You can, of course, heat your home with electricity, and most of us in Florida do. We have terribly inefficient heating coils built into our air conditioning systems. By the very nature of these systems, it is impossible to turn 100% of the electricity consumed into heated air, much less convert 100% of the . The conversion from solar radiation -> electricity -> heat is even more inefficient than the solar thermal process of space heating in a home.

With that said, it is really the only practical option today to heat homes in Florida with solar electricity. The nice thing about using solar electric panels is that they will offset your heating costs when you need to heat your home, but will also provide energy for everything else in your home when your heater is not running. Since you probably already have an electric heater built into your air conditioning system, you do not need to buy any additional equipment to provide reliable heat on demand, and there are no additional moving parts required.