Reversible air-conditioner / heat pump schematic Heat pumps are high in the public eye in New Zealand 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 approaches freezing point this efficiency declines);
  • Provides heating in winter and cooling in summer;

However, worldwide interest for heat pumps has declined markedly since 2010 and research is all but absent in Europe (please check this link to see the source data from Google).  This is with the exception of New Zealand, which now represents the largest area of online search in the world. 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 New Zealand consumers too?
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.

European experience shows these systems once above 16kW (required to heat a whole house) to work poorly on domestic single-phase, requiring high inductive load and producing demand spikes. Above 16kW really requires 3-phase supply;
As a retrofit system into a house with an existing system, purchase and installation costs are high due to:

  • Requirement to site the external unit as unobtrusively as possible;
  • Invasive installation (due to the requirement to route refrigerant and wiring to each distribution unit);
Heat pump external compressor

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;
  • They make noise, especially when on their defrost cycle;

Other issues with heating air:

  • Only effective when on. If the distribution units are turned off, then you quickly revert to a cold house;
  • Do not work effectively if the property is poorly insulated. Older NZ homes are subject to high thermal and air infiltration losses (drafts) which work against the efficiency of heat pumps;
  • Uncomfortable when in direct path of heated air;
  • Warm air convected over cool building fabric is a key contributor to damp and mould;

Herschel Infrared as an alternative to heat pumps:


Select XL Glass panel in a living room
  • 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’



  • Heats only, not for cooling;