Minimum cost for external works (drilling) will be $25,000 if drilled vertically and $15,000 if a horizontal installation, for a home of around 160 sq/m of conditioned space. A 400m2 home will be around $40,000 for the drilling and ground installation only.
It costs more if a pool is heated and will vary depending on the location of the site in Australia and home much demand for heating & cooling. There are many variables.

In the USA, regulatory and industry authority ASHRAE suggest using a GSHP time of use +22 years prior to replacment. They last a long time as they do not work as hard as an air source heat pump which can experience compressor fatigue anytime post 13 years.

Minimum land area for an average home would be around 15 metres x 25 metres of open ground. Costs are around 30% less than drilling if you can find a contractor to do the work in your local area.

We consider that an 8 to 18 year payback is the realm in which heat pumps offer a return on initial up front costs. It all depends on how much one uses their AC, pool heating, hot water heating etc. There are, however, many other benefits that people consider such as silent operation, general longevity of the heat pumps and lower energy use to induce longer life from battery storage systems.

Yes. Depending on the project requirements, a system can be designed to provide one or all of the listed requirements from one single Ground Source Heat Pump unit. Typical sizes range from 6kW to 21kW units for residential systems. Commercial systems can be provided up to 500kW, with more common sizes being from around 50kW to 100kW.

Yes. However, depending on the gas boiler currently being used and design temperature you may need to also replace some components of your house heating delivery components. This can include radiant panel heaters. Some are designed for high temperature water, produced by gas boilers (70 degrees Celsius) and are therefore smaller and have less surface area. These may not be able to heat as effectively as a larger style radian panel which is made for low temperature water. Heat pumps will produce very efficiently water below 50 degrees C, which is enough to provide heating to any building.

Yes. However, depending on the size of your block and usable ground surface area you may be limited to the size system installable. Different types of geothermal systems can be applied. See the Geothermal Solutions page for details on types of ground loops.

Yes. You can combine Ground Source Heat Pumps (GSHP) with Air Source Heat Pumps (ASHP) in the same house or building. Larger scale jobs in Australia will typically combine technologies and use geothermal as a base load energy source with air source units (conventional air conditioning units) assisting for peak load cooling and sometimes heating.

Yes. However, the size of the system you can use may be limited by the size of your standalone power supply. An energy analysis is needed to determine the capacity of battery storage system that would enable operation of the heat pumps in peak load periods.