Sustainable Heating and Cooling Options

A heat pump does not create heat, it moves it, which is why it can deliver 3 to 4 units of heat for every unit of electricity it draws. A combustion appliance cannot beat 100 percent by definition, and in practice a gas heater converts roughly 80 to 92 percent of its fuel into useful heat. That gap is why every serious decarbonisation pathway for housing goes through heat pumps.

The same technology covers space heating, cooling and hot water. A reverse cycle system heats and cools the house, and a heat pump hot water unit uses roughly a third of the electricity of a conventional electric storage tank. Between them they typically account for the majority of a household energy bill, which is why they come first and everything else comes later.

Every refrigerated system contains refrigerant, and refrigerants differ enormously in their impact if they escape. Most equipment now sold in Australia uses R32, which has roughly a third of the global warming potential of the R410A it replaced, and systems using it typically need less refrigerant to do the same work.

What matters practically is that the charge stays inside the system. That comes down to installation quality, brazed and pressure tested joints, correct evacuation, and recovering refrigerant properly when equipment is decommissioned rather than venting it. Refrigerant handling requires an ARC licence for exactly this reason. If you are replacing an older R22 or R410A system, the recovery of the old charge is part of the job, not an optional extra.

Electrifying heating and hot water changes the shape of your electricity use, which changes what solar is worth to you. Exported energy earns very little now, so the value is in self consumption, using the power while your roof is making it.

That is easy to arrange with hot water. A heat pump hot water system on a timer that heats in the middle of the day runs largely on your own solar, which is a much better outcome than the traditional overnight controlled load approach. Space heating is harder because you want it in the morning and evening. Pre heating the house in the early afternoon on a sunny winter day helps more than people expect, particularly in a home with reasonable insulation and thermal mass.

The building envelope comes first because it reduces the size of everything you buy afterwards. Ceiling insulation, sealing obvious draughts, and fixing separated or crushed ductwork all reduce the capacity you need. Doing that after buying equipment means paying for capacity you did not need.

Then the appliances, usually heating first because it is the biggest single load, then hot water, then cooking if that matters to you. Once the last gas appliance is gone the gas service can be disconnected and the daily supply charge stops. Solar sizing is best reviewed at the end, when you know what the electrified household actually consumes, rather than guessed at the start.

Do not replace equipment that is working well just because a newer version exists. A ten year old reverse cycle system in good condition is not an environmental problem, and the emissions and cost of manufacturing a replacement are real. Service it, keep it running, and replace it when it fails.

Do not oversize on the theory that bigger is greener. An oversized system short cycles, runs inefficiently and costs more to buy. And do not disconnect gas before the replacement appliances are installed and commissioned, because reconnection is expensive and winter is not the time to find out the sequencing was wrong.