Information Sheet


The heatsource (sometime called boiler) is the main component of any heating system with many different options to choose from.

Gas (Natural and LPG)

Properly the most used heatsource for heating around the world and have come along way from the cast iron lump that sat in the corner of a kitchen. These days they have very good efficiency ratings especially condensating models which over the next few years will be the only models available. Currently you can choose between condensating and non condensating, system or combi, internal or external units.

Non condensing units are slightly cheaper to buy but not as efficient and in certain countries are already not available anymore, but they work in the same way as the condensing models the difference is a condensing model is more efficient by using waste heat in flue gas to preheat cold water entering the boiler, which makes condensing models 15% more efficient than non-condensing models and will cost less to run.

System boilers are primarily a heating only unit they require a separate cylinder for storing hot water however all the main components of a heating and hot water system are built into the unit making for a easrier install with no requirement for feed and expansion tanks.

Combi boilers provide both hot water and heating in one compact unit and therefore have no need for a separate cylinder for storing hot water.

Both these types of boilers are available in condensing and non condensing options.

LPG units have greater running costs to due to the cost of the fuel and the storage bottles.


Work in much the same way as gas units and are also available in condensing and non condensing models and both system and combi variants.

External units are a popular option taking the heatsource out of the house, diesel boilers (or oil boilers as known in other countries) older models were sometimes nosier than the gas equivalent and had an associated aroma about them, which is not the case with the modern units.

The key is to ensure that the units have been set up to work with New Zealand fuel as the requirements are different to the set up overseas.

Air to water Heatpump

heat pump takes the available heat from the ground or air surrounding a property and increases it to a more useful temperature for use in the home. This renewable source of heat can be used to create warm  water (for central heating) as well as hot water (for both central heating and domestic hot water supply).

It achieves this by taking the same principle that allows a fridge to cool your groceries and by utilizing it in reverse.

The source of heat, outside air or pumped over the heat exchange surface of the outside part of the heat pump.

This heat (although cold in comparison to a homes internal air) is warm enough to cause the special refrigerant liquid to evaporate and turn into a gas.

This gas is then put through a compressor which increases the pressure of the gas, a factor that causes its temperature to rise. For example you may have noticed that a bicycle pump, gets warm when it is used, the gasses in a heat pump experience the same temperature rise due to compression.

The gas (now heated) is passed over the internal heat exchange surface. This heat is transferred into a home’s central heating or hot water system.

The gas falls in temperature as the heat is transferred into the home and it subsequently returns to a liquid state.

The refrigerant returns to the outside heat exchange surface and the process repeats itself until sufficient heat is passed into the home.

Geothermal Heatpump

Works in the same way as Air to Water HP except it takes its heat from the ground rather than the air via a water mix contained within ground collectors or pipes, Geothermal is a more costly install but the efficiency is better as the temperature in the ground is more stable than air temperature.

Solid fuel

Two main types, Atmospheric and Gasification boilers. Certainly, a good choose for those with good wood supply at hand.

Atmospheric are natural draft flue units whereas the Gasification are fan controlled leading to a clean burn process making them more efficient.

Both require more work from the house owner with having to fill the fire box with wood to keep the temperature constant.