Independent hot water generation
Turning Sunshine into Hot Water in New Zealand
With SOL•THOR, a family home in Auckland converts solar electricity directly into domestic hot water.
Facts about the project
- Planner
- Photovoltaic capacity
- Number and type of modules
- Thermal Storage Size
- Building type
- Building Type
- Installed my-PV Product
- Heating Element
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In Auckland, New Zealand, a residential home from the 2010s demonstrates how photovoltaic energy can be used efficiently for domestic hot water generation. Implemented as part of a pilot project supported directly by OneEnergy, the installation showcases how a compact PV system combined with a my-PV power controller can significantly reduce conventional energy consumption.
The photovoltaic system has a capacity of 2.7 kWp and consists of six Suntech modules rated at 440 W each. The generated solar electricity is used directly for hot water production via the DC Power Manager SOL•THOR. Instead of feeding surplus electricity into the grid, the system converts it into usable heat in a 180-liter electric hot water cylinder equipped with an existing 3 kW heating element.
Personal customer opinion and resumee
The customer is very satisfied with the system and highlights two main benefits. First, the ability to make effective use of solar energy for hot water production. Second, the opportunity to shift energy consumption into more favourable tariff periods. Overall, the solution demonstrates a clear economic and practical advantage for the household.
What led to the decision to use my-PV?
The choice of photovoltaic-based water heating is also closely linked to the current energy market situation in New Zealand. Gas prices have been rising steadily a 45 kg gas cylinder currently costs around NZD 170 (approximately €85). Electricity prices typically range between NZD 0.20 and 0.25 per kWh (about €0.10 per kWh). Overall, energy prices have increased by around 30% recently, making gas-based hot water systems increasingly expensive to operate.
By using PV electricity for hot water generation, the household can produce and consume a large share of its required energy on-site. This significantly reduces dependence on external energy sources and the associated costs.
Were there any challenges during installation?
The installation of the PV system was straightforward overall. During the early commissioning phase of the SOL•THOR, some uncertainties arose. These were quickly resolved through firmware updates provided by the support team. After completing the updates, the system has been operating reliably and has remained stable ever since.
How many people live in the household, and what is the hot water demand like?
The household consists of two adults and two teenagers. With a total of four occupants, the hot water demand corresponds to that of a typical family household.
Is grid electricity used as a backup for hot water generation?
Grid electricity is available as an additional heat source for the system. However, the household does not use tariff-based heating schedules. Instead, only a legionella protection boost is activated at 5:00 PM if the tank temperature has not reached a certain level. Under normal operation, the SOL•THOR acts as the primary heat source for the hot water tank and covers the majority of hot water production.
What are the benefits of switching to photovoltaic-based water heating?
After just over one year of operation (commissioned in February 2025), the potential of photovoltaic hot water generation is clearly evident. The total annual energy demand for hot water amounts to 4,072 kWh, of which 2,627 kWh were supplied directly by solar energy—corresponding to a solar share of approximately 65%. The remaining 1,445 kWh were provided by grid electricity. Solar yield peaks in summer, most notably in December, when grid use is minimal, while in winter months the share of grid energy increases due to lower PV output. Overall, the chart below highlights a strong and consistent solar contribution throughout the year.
As a result, a significant portion of the household’s hot water is produced using locally generated solar energy. The achieved cost savings lead to an estimated payback period of around three years for the SOL•THOR, in addition to the long-term savings resulting from the high solar coverage.
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SOL•THOR
in use
The DC Power Manager converts solar power directly into heat – efficiently and with minimal loss by using direct current from PV modules to power a heating element.
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