Reverse Cycle or Gas Heating?

With summer on us, we are being asked about fitting central heating systems to several of our houses. One of them already has a gas heating system, and someone suggested removing the gas heater and replacing it with a reverse cycle system, claiming running costs would be less.

However Murray Keller of Combined Heating and Cooling said, absolutely not! He recommended fitting an electic cooling system to the present gas heater, which would be a more expensive solution in the short term but much more effective and cheaper to run.

I asked him to explain and what he said made a lot of sense. Reverse cycle systems are heat pumps. When it's hot inside your house, they suck heat from your house and blow it outside. When it's cold inside your house, they suck heat from outside, and blow it into your house.

When it's hot there is lots of heat to pump, so the system is very effective. When the temperature outside is, say, 15 degrees C, the pump can work efficiently either way.

But when the outside temperature falls below, say, 10 degrees there just is not enough energy available for the heat pump to suck heat out from the atmosphere to blow into your house. In the ultimate the system goes into Defrost Mode and shuts down.

Running costs of the reverse cycle system in cooling mode are admittedly lower when it's warm, but the cost rises rapidly as the outside air temperature falls, at the same time as the system becomes increasingly ineffective.

Food for thought. After reflection, I will be advising the owner to go for the added cooling unit!