May 3, 2023
◼ Heating rod in combination with balcony power plant?
Balcony power plants are getting more and more popular due to their easy implementation. But what to do with the surplus – is a heating rod an alternative to water heating here?
Balcony power plants are usually small photovoltaic systems that can have a maximum output power of 600 watts (in Germany) or 800 watts (in Austria) from the microinverter. Connection and commissioning is simple, the cost savings are easy to calculate and the investment – compared to a larger PV system – is very manageable. There is no complicated registration or permit requirement, which means that it is a simple way to reduce electricity costs – even in apartments.
Use electricity from the balcony power plant yourself
In contrast to a grid-connected photovoltaic system, which has a yield of several kWp, there is no feed-in tariff for the balcony power plant with the grid operator. This means that any surplus that is not consumed directly on site goes into the public grid without compensation.
What if all consumers in the household are supplied with the power from the balcony power plant and there is still a surplus?
As it is usually the case with larger PV systems, a heating element could heat the hot water during the day in order to make the best possible use of the sun’s energy. However, the PV surplus from the balcony power plant is not sufficient to generate hot water.
A small potential analysis: A balcony power plant with 800 watts supplies around 2 kWh of energy in spring or autumn with a south-facing balcony on a nice day. In the case of an average single-family house, however, this yield goes almost entirely into the base load of the house, and there is no more energy left for heating water.
Hot water with photovoltaics is still possible!
The balcony power plant can (unfortunately) only be regarded as a relief for home consumers or the conventional power supply. For hot water preparation, we suggest additionally or alternatively using the off-grid variant of a solar-powered heating element, which is linearly controlled, if space permits. Instead of a balcony power station module with an integrated micro-inverter, 4 to 8 standard modules with MC4 plugs can be used, and with the ELWA from my-PV, the direct current can be used directly for hot water preparation without an inverter. Solar energy can this way be used without a permit, since the PV modules are not connected to the public power grid, but are only used to heat water. The linearly controlled 2 kW heating element, our ELWA, also has enough power to cover the hot water preparation between March and October with solar energy alone – this is even shown by this reference project in Denmark, for example!