living off the grid 

"It has been,overall, as straightforward as it could possibly have been, although the complexities of an off grid system have at times seemed daunting!"

Rural location in Wanaka, 200 sq/m floor size, 2 occupants

As it is a holiday home now but a permanent home in the near future, the brief from our clients was to be able to have heating and hot water to their home that was responsive and sustainable.

>500L Rotex Sanicube thermal store
>Off-grid photovoltaic solar with battery storage
>Thermalux Linea 20kW wood fired boiler
>Rinnai Infinity gas water heater
>Underfloor heating with Neostat thermostats
>Radiator heating

The design incorporated photovoltaic solar with batteries, a wood fired boiler, a gas water heater and a 500L Rotex thermal store. This installation allowed for underfloor heating, radiators and hot water for the 200 square metre home.

The main living, dining, kitchen, atrium/entry, library, hallway, mudroom, bathroom and ensuite are heated by underfloor pipework to provide low temperature heating to the main areas. To provide flexibility to the heating, the three bedrooms have radiators that can provide a quick response when needed as not all of the rooms will be used.


The wood fire provides heat to the dining/kitchen and there is an Escea gas fire in the living room, also for low energy and quick heat or just for ambience if needed.


The Rotex Sanicube thermal store is the hub for the hot water and heating and can collect the energy from various sources and deliver the heated water to various locations/requirements. The main source of hot water for the thermal store in winter is a Thermalux Linea 20kW wood fired boiler. 

The Thermalux Linea fire has a glass front as a normal freestanding fire would have, but instead of a standard wetback, the fire has a water jacket that sits on three sides of the fire box and is able to generate up to 20kW of hot water quickly and deliver up to 8kw of heat to the room . The heated water is delivered to the thermal store by a low energy pump (this can be by gravity if close enough) and heats the thermal store directly without a heat exchanger. 


The photovoltaic solar also adds to the heat source of the thermal store via an electric element and as a back up and a very quick recovery. There is a Rinnai Infinity gas continuous water heater also connected to the Rotex thermal store. All three sources of energy are set up to contribute to the heating and hot water for summer and winter, with the solar contributing most, if not all, hot water in the summer with the gas backup and the wood fire and gas backup for the winter, with the solar contributing what it can in the winter months.

The photovoltaic panels provide all the energy to power the home with the batteries providing the extra power source for evenings. Any excess energy from the solar is directed to the Rotex thermal store to heat the water and in effect also acts as a “battery” using all the excess energy to generate hot water.


All power generation and consumption need to be monitored carefully to make sure the home can have continuous power; and careful selection of energy efficient appliances, LED lighting, low energy pumps, gas cooking etc was required at the very beginning of the planning process with the clients and architects.

The architects ensured the home has high insulation values with R4 in the walls and R5 in the ceilings and high quality windows and doors to minimise the heat losses of the home; and the orientation of the home maximises the sun available in summer and winter. 


Most of the rainwater from the roof is reticulated into an in-ground water tank to use for the domestic water and for irrigation to minimise the use of the solar bore pump. The irrigation is minimal to conserve the water for domestic use. 



This home has all the comfort of a grid connected home using the renewable energies available to this rural property. The wood fire running most of the day will provide a lot of the heating and hot water leaving the solar to work on the power consumption of the appliances and batteries in the winter.  


"Just wanted to convey our thanks to you and your team for your contribution to our project. It has been,overall, as straightforward as it could possibly have been-although the complexities of an off grid system have at times seemed daunting! Kurt and all the others have always been obliging and helpful-including with the ongoing fine tuning of the system."


Download information sheet on the Rotex Sanicube Thermal Store.