Reversible air-conditioner / heat pump schematic

What are they?

Heat pumps are high in the public eye in Oceania as an energy-saving heating and cooling system.

They comprise a compressor unit mounted on an external wall which draws outside air through a heat exchanger to warm or chill a refrigerant.

This refrigerant is then piped to each of the distribution units within the house where further heat exchange occurs with the house’s internal air to either cool the air in summer or warm the air in winter.

Heat Pump Advantages

The advantages of heat pumps are:

  • “kilowatts out” in terms of heating effect are between 3 – 4 times “kilowatts in” (though it is important to note, when the ambient temperature is very hot or very cold – i.e. when you want to use it the most – this efficiency declines. European experience suggests the ratio is never greater than 1:1.6 on average);
  • Provides heating in winter and cooling in summer;
  • Can heat your hot water.

However, worldwide interest for heat pumps has declined markedly since 2010 and research is all but absent in Europe (check this for yourself on Google Trends). New Zealand actually represents the top worldwide search location for Heat Pumps (Index = 100) with Australia 7th (Index = 5). So the question is – for what reasons is the rest of the world going cold on heat pumps? – and should this loss of interest be sounding a note of caution for consumers in Oceania?

Worldwide google trend for heat pump research

Heat pump disadvantages

Load damage from heat pump
Load damage caused to domestic 60 Amp electric distribution point by 16kW heat pump.

Heat pump external compressor




European experience shows that heatpumps over 16kW (required to heat a whole house) work poorly on domestic single-phase, requiring high inductive load and producing demand spikes (see title image). Above 16kW really requires 3-phase supply;

As a retrofit system into a house with an existing heating system, purchase and installation costs of heat pumps can be very high due to the need to site the external unit as unobtrusively as possible; route coolant pipework and electrical cable into the house and up to the various distribution points.  The retrofit costs can easily eliminate any saving available from the lower running costs of the heat pump for a long period of time.

As a result, payback periods versus other solutions are long (10yrs+), regardless how cheap the energy consumed is, making these a more expensive lifetime cost and poorer investment proposition than Herschel Infrared which will typically pay back within 3-5 years; Heat pumps require annual maintenance and cleaning of air filters. Moving parts wear-out over time. Certain system failures will stop the whole house being heated or cooled;

Heat pumps are also noisy, especially when on their defrost cycle.

Other issues with heating air

  • Heating air is only effective with the units switched on (and consuming energy). If the distribution units are turned off, then you quickly revert to a cold house.
  • Heat pumps do not work effectively if the property is poorly insulated. Older Australian and NZ homes are subject to high thermal and air infiltration losses (drafts) which work against the efficiency of heat pumps.
  • It is uncomfortable being in the direct path of the heated air.
  • Warm air when convected over cool building fabric is a key contributor to damp and mould.

Herschel Infrared as an alternative to heat pumps

Herschel Heaters in living rooms


  • Purchase and installation price of infrared are much less than the cost to purchase and install Heat pumps;
  • Can be run from domestic solar and wind installations therefore being “free” (impossible for heat pumps);
  • The heat transfer efficiency of Infrared is superior to hot air, with no infiltration losses, meaning less wattage is required for less time – dramatically reducing the energy efficiency argument of heat pumps in real world use;
  • No maintenance requirements over the product’s lifetime;
  • Total cost of owning Infrared over the product’s lifetime is lower than for heat pumps and lower capital outlay also means payback times are quicker.

Other Advantages

  • Discreet design. Panel disappears as a heat source once the building’s thermal mass is established;
  • Silent operation;
  • No air movement means a more comfortable environment for all;
  • Our bodies absorb this far-infrared heat deeply all over, no more hot stuffy air and still feeling cold;
  • ‘Set and forget’ operation, use with a room thermostat for simple operation and highest efficiency;
  • Heats and dries the building fabric, removes damp and mould;
  • Far less susceptible to heat loss through drafts; allows ventilation without heat loss;
  • Cost efficiently warms your home ‘around the clock’.


  • Heating only, not for cooling;
  • Does not heat your hot water.