A summer break for your heat pump
Why a heat pump and a solar immersion heater are not a contradiction – but a good team all year round.
Key points
- From spring to autumn, the 1 kW solar immersion heater can take over most of your hot water – the heat pump takes a break.
- Solar power flows as direct current straight from the panels into the heater. No inverter, no registration.
- Fewer short starts in summer take the load off your heat pump's compressor.
“I already have a heat pump – why would I need a solar immersion heater?” We hear this question almost every day. The short answer: both devices are strong in different seasons. Together they cover the whole year.
The heat pump is a marathon runner
A heat pump is built to heat steadily for many hours in winter. In summer the house needs no space heating – only hot water. The heat pump then often switches on briefly to top up the tank and switches off again. This cycling puts strain on the compressor.
On top of that, hot water needs higher temperatures than underfloor heating. The higher the target temperature, the less efficiently the heat pump works.
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Solar power on the shortest route
The 1 kW solar immersion heater connects directly to two to four solar panels. The panels' direct current flows straight into the heater and becomes heat in the tank. There is no inverter, no meter and no connection to the public grid.
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To be honest: in pure efficiency, the heat pump wins – it turns one kilowatt hour of electricity into more heat than any immersion heater. The 1 kW solar immersion heater's advantage lies elsewhere: its electricity costs nothing, because it comes straight from your own panels. And your heat pump gets to take a break.
The heat pump for power in winter. The solar immersion heater for summer.
No registration, no paperwork
Because the 1 kW solar immersion heater works as a stand-alone system and does not feed into the grid, there is no need to register it with the grid operator. Plug in the panels, choose the temperature, done.
Checklist before you buy
- A free socket on the tank: The 1 kW solar immersion heater needs a 1½-inch socket (G 1½, also called 6/4 inch) and is installed horizontally.
- Space for panels: 1,500–2,500 Wp is recommended, usually four standard panels – on the roof, balcony or in the garden.
- The right voltage: The panels need an open-circuit voltage below 50 V. More in How many solar panels do I need?
How much the sun takes over depends on your consumption, the orientation of the panels and the weather. In winter, your heat pump keeps heating as usual.
