Heating a garage

In Canada because of the huge demands for winter heating, solar heating can be very costly. that's not to say it can't be done, just don't expect it to cost less than a $1000 gas furnace or normal natural gas hot water boiler!

It really all depends where you live.  Obviously heating a garage in Vancouver is much easier than in Alberta.

Heating a Workshop/Garage

If you have a workshop or Garage, the area can be heated with Solar Panels. It depends on if you just want to warm it a bit or turn it into a sauna.

For example, a 30ft x 20ft Workshop with R20 Insulation could be kept about 20 Deg.C above outside temperature with approximately 2 panels but in Alberta it is likely to take more.

Rough Calculation / Estimate


  • 572 ft2 shop. (25ft x 23ft)
  • Assuming 10ft ceiling.
  • R value of 20
  • Temperature differential required between inside and outside at 36 Deg F (approx 20 Deg C)

This would give a heat loss of approx 3322 BTU/hr

Over 24 hour period this is (x24) = 79747 BTU per Day

Assuming the sun shines 8 hours a day you have to get 79,747 BTU over an 8 hour period, hence you will need approx 79,747 / 8 = 9968 BTU per hour to heat the shop.

You will need to store this heat and release it through the night (ie water storage tank and/or concrete floors)

If you have a concrete floor with infloor pipes then this will help. You can either run the glycol mixture direct through the floor or store the hot water in a tank and then pump the water from the tank through the floor.

Number of Panels needed.

This will vary a lot depending where you live in the country. TO carry out the heat loss calculations above will involve some work, or you will need a bit of trial and error.

In summer the collectors can produce nearly 8000 BTU per hour, however you are not going to need to heat the garage in Summer. In winter the number can be 4000 or 5000 BTU/hour on a very cold clear day.

If you live somewhere warmer, then the winter is likely to be much cloudier but you will also not need as much heat to warm the garage.

Hence you should need about (9968 / 4200 ) 2.4 panels + about 50 gallons water storage per Panel.

Remember this is a rough back of a napkin estimate. This will be affected by the number of door and windows, how much insulation, any machinery in the shop that gives out heat. There are dozens of factors that affect the heat loss and its not possible to guess them for your building. This is just a very rough guide.

Remember..... this is heating the shop to about 20 Degrees C above outside temperature. If it is 40 Deg.C below outside then it will still be 20 Deg.C above the outside ambient temperature, which if it is -40 outside then the garage will still be -20 below even with the heating. Therefore, it is difficult to heat a home or building in Alberta with solar.

If your home or building is in a warmer part of the country, then the task gets much easier.

Client Comment

Comments from people who have installed evacuated tube solar collectors on a workshop in Calgary for winter 2010 said this...A single 30 tube collector was installed on a south facing garage and the fluid was pumped direct through the in-floor heating.

''I can say that it has made a difference, but you aren't going to break a sweat in there. When the temps dropped down to -35, it didn't come close to keeping up.  But by the same token that has been the only time it has gone below freezing in there."