I currently has a propane gas patio heater. Its design allows a massive amount of heat to escape upward instead of being reflected downward due to its use of combustion to produce heat.

I would like to replace the unit with a soffit mounted linear electric heater. You can see a picture of both the current heater and the spot where I would mount under the soffit below:

Existing conditions

The gas unit is rated at 42,000 BTU/hr. However, clearly it loses a lot of its heat as convection away from the unit since much of the heat produced is combustion products rather than infrared that is reflected back at me.

What wattage electric model (which presumably is more efficient in producing infrared rather than heating the air) would best replace the existing unit?

  • I have installed several infrared electric out door units, they may be more efficient but cost quite a bit, the ones I have done out doors or that were listed for damp locations ran in the 500-1000$ ranging from 2500w to 5000w they did a better job according to the owner but his wife said they were much more expensive to run than there gas one. I believe the electric ones will last longer after looking at there old one and the construction of the electric ones, just make sure to get ones listed for outdoor use many are not. – Ed Beal Feb 7 '19 at 21:05

42000 BTU/hr would be about 12,300 kW/hr. The best way is to replace the heater with a one or more infra red heaters up to the required amount of heat you need. If you place more heaters you could position them on different spots. Only where required. I would start with 4 units of 1500 W and then see where you arrive.

Please keep in mind that you should seperate the heaters over different groups. This to prevent to problems with your breakers and wiring.

  • You can't convert 42,000 BTU/hr directly to 12,300W because of the significant differences in efficiency between the two units. The electric ones will be substantially more efficient. – David Pfeffer Apr 22 '17 at 15:03

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