"We are thrilled to now have everything operating so well, with power accounts a delight to receive, in this highly specified energy efficient home of the future"

Wanaka location, 325sq/m floor size, 2 permanent occupants

We worked alongside the architect, Chris Prebble of Three Sixty Architecture, to design and install the plumbing, heating and energy integrated system for their exceptionally designed home. The brief was an energy efficient, low cost system to run and maintain, with a low environmental impact. The owners already had an idea of what they were after, so Kevin refined and designed a high end system which met this brief. We also did the plumbing and drainage for this home, completing our total package service. 

> 500L Rotex Thermal Store
> 16kw Grant Aerona Air-to-Water Heat Pump
> Underfloor Heating to 5 Zones
> Heatmiser Neostat Thermostats x 5
> 5kw Solar PV System - 20 x 250W Micro Inverter Panels, Fronius Primo Inverter (converts power from DC to AC) & Power Genius (monitoring & control)
> Ring Main

The central heating and domestic hot water system revolves around the Rotex. The Rotex Sanicube is a 500L thermal store which collects the energy from various source and disperses the heated water to various sources. Using the stratification within the tank allows the use of various heating and hot water requirements to be met with maximum efficiency e.g. the bottom of the tank is 30-40°c (used for underfloor heating with the lower temperatures, pools and spa pools), middle/top of the tank 40-60°c (used for domestic hot water and any other high temperature appliances).For this particular system, the energy sources are;

> 5kw PV Solar System;

> Electric Element;

> Air to Water Heat Pump.

The system has been set up to maximise the use of the PV Solar first, then use the Air to Water Heat Pump to make up the temperature difference and boosting required for the demand required for the hot water and the heating. The 5.5kW solar system provides around 25-30kW per day in the summer (potentially more) and around 5-10kw in the winter depending on the sunshine hours available (some days are less in winter if it is overcast). 

The PV solar is monitored to check the trends, power generation and consumption of energy used within the home. The ultimate outcome is to match the generation and consumption as closely as possible to minimise import or export of power to and from the grid.

The PV will generate power to the home appliances first, meaning whatever power is required for the home, the solar generated power will go to the appliances being used.


Whatever excess power is left over will be directed to the Rotex heating element to heat the hot water via the ‘Power Genius’. The ‘Power Genius’ is connected at the switchboard, automating and ensuring that all power generated is being used within the home and not exported – this means available power is utilised to maximum efficiency. If there is any excess after the home and hot water has been taken care of, only then generated power is exported to the grid. The Power Genius controls where all generated power will go to. If there are smaller amounts of excess power (power not being used for appliances) the Power Genius will divert this to the Rotex electric element to heat the Rotex directly. If there are larger amounts of power available, the Power Genius will divert the power to the heat pump due to the higher efficiency rating of the Air to Water Heat Pump. During cooler months, when the Rotex is already up to required temperature, the Power Genius can switch on the underfloor heating circuits certain underfloor zones to ‘dump’ excess generated power, rather than send to the grid. This is manually controlled via the Power Genius dashboard.

The electric heating element draws energy from the PV solar, or from the grid, to heat the hot water for the top and middle of the tank with a lesser amount at the bottom of the tank. The Air to Water Heat Pump provides heat and energy to the Rotex only. This is to maximise the use of the PV Solar energy first, then utilise the heat pump to top up or boost the Rotex to the required temperature. In winter, the heat pump will be used more often due to the heating demand in the floor.

The ring main has a Grundfos comfort pump installed on the hot water line. The ring main pump has a memory which picks up the daily usage and activates the pump prior to the normal usage time and turn off when the water is no longer required. This is to minimise heat loss from the heat source (Rotex) and save energy for hot water recovery and pump running time.


The client only leaves the underfloor heating on in the areas they are living in, set to 21°c. As this is a reasonably new home, exact running costs haven't been determined yet but we will have some specific data next year. The client is going to put insulated boxes around the exterior pipes (these are already lagged but losing some heat) which should increase efficiencies. 

> Technician maintenance - all central heating systems should be serviced annually to maintain efficiency. An average air-to-water heat pump service costs $200 + GST. 
> Client maintenance - the pressure in the system needs to be kept topped up for the system to operate. Occasionally, this may drop and need to be topped up. This is a 10 minute task and we provide our clients with an manual specific to their system with instructions on how to do this. 

"We are thrilled to now have everything operating so well, with power accounts a delight to receivein this highly specified energy efficient home of the future".


Download brochure on the Rotex Sanicube Thermal Store.


Download brochure on Heatmiser range or visit website: https://www.heatmiser.com/en/neo-smart-thermostat/


Download brochure on the Grant Aerona Heat Pump supplied by Waterware


Download brochure on the Jinko PV Solar Panels supplied by Sunz


Download brochure on the Fronius Inverter supplied by Sunz


Visit the Power Genius website to learn more about solar monitoring and control.