Photovoltaics with heating element

PV heating element and complete systems from PVundSO

With a PV immersion heater, excess solar power is used to heat water instead of being fed into the public grid for just a few cents per kilowatt-hour. The heating element is located directly in the hot water storage tank and can convert every available kilowatt-hour into heat. Your storage tank thus becomes a thermal storage unit for solar energy, significantly increasing your system's self-consumption. The category of photovoltaic systems with immersion heaters includes individual heating elements, power managers, and measuring technology, as well as complete, ready-to-use systems in which solar modules, controllers, and heating elements are already perfectly matched.

Two complete systems are currently available. The smaller one combines six modules, each with at least 445 watts, and the my-PV DC ELWA, a continuously variable 2 kW solar heating element, for €1.499. The larger set, with eight modules, the SOL-THOR power manager, and a 3 kW heating element, costs €1.999. Both packages operate without an inverter and without grid connection; therefore, registration with the grid operator is not required.

The range of heating elements covers outputs from 2 kW to 9 kW. Whether a heating element is used to expand PV systems with or without battery storage is irrelevant for this technology. A control system continuously monitors power generation and supplies the heating element only with the amount of power that is currently available.

Buy a PV system with a heating element and reduce energy costs.

Photovoltaics with an immersion heater offer significant savings, especially where gas or heating oil is currently used for hot water. A single-family home with four people requires roughly 3.000 kWh of heat per year, which, at 12 cents per kilowatt-hour of gas, equates to approximately €360. If solar power covers half to two-thirds of this amount, the household saves roughly €180 to €240 annually. Extrapolating this over 20 years, the savings amount to at least €3.600, not including future price increases for gas and oil.

If you start with a complete system, the cost for hot water with a photovoltaic heating element from PVundSO starts at €1.499. In the gas example, this package pays for itself after about 6 to 8 years. If modules are already installed on the roof, a single PV heating element with a suitable controller is often sufficient. Heat is significantly cheaper to store than electricity. A PV system with a heating element is therefore a cost-effective alternative to expensive battery storage. The size of your system depends primarily on your daily hot water demand.

Efficiently generate hot water using a photovoltaic heating element

Hot water is produced directly using a photovoltaic heating element, as an electric heating element converts almost 99 percent of the electricity into heat. In contrast, thermal solar collectors lose energy during hot water preparation through heat exchangers and long pipes. This high efficiency makes the technology particularly attractive for small and medium-sized systems. Since the units fit into standard hot water and buffer storage tanks with capacities between 200 and 500 liters, a new tank is usually unnecessary. For heating support via the buffer storage tank, there is a dedicated solution: a heating element specifically designed for buffer storage tanks .

Temperature sensors limit the storage temperature and protect against overheating. With a power output of 3 kW, a heating element heats 300 liters by 40 degrees Celsius in just under 5 hours. The my-PV DC ELWA and the SOL-THOR operate with direct current (DC), so the heating element receives photovoltaic power directly from the module, without an inverter. For grid-connected systems, there are AC solutions such as the AC-THOR, which uses PV power from the household electrical system. All details about the DC principle can be found on the page "DC Heating Element PV".

As long as the sun is high in the sky from April to September, 4 to 5 hours of sunshine on clear days are often sufficient to fully heat the storage tank. During this time, a photovoltaic immersion heater for hot water largely covers the needs of many households on its own. In winter, the yield is lower, and the main heating system then takes over the shortfall.

Heating element for the PV system: control and PV surplus

To monitor the current power feed-in, the control system for a PV heating element uses a meter at the house connection, such as the my-PV WiFi Power Meter. Once the household's base load is covered, the power manager continuously distributes the excess solar power to the heating element. The AC-THOR regulates between 0 and 3 kW and operates fully automatically, so you don't have to switch anything manually. This precise power control avoids grid draw and utilizes the surplus power with maximum efficiency.

Between 10 a.m. and 16 p.m., when the modules deliver their highest output, a heating element powered by excess PV energy runs most frequently. Once the target temperature is reached, the system switches off, and the remaining electricity is available to other appliances. In this way, a smart heating element utilizes excess PV energy within the home instead of feeding it into the grid. If multiple appliances are to receive solar power according to predefined rules, an energy management system like the VOLTRADER Core HEMS distributes the surplus.

Existing systems can be retrofitted without major modifications, as it usually suffices to insert the heating element into the storage tank and connect the controller to the meter. Therefore, a heating element complements PV systems of any size. The AC connection should be handled by a qualified electrician, while the DC sets are connected to the modules via MC4 connectors. For new systems, a suitable heating element for the PV system and storage tank should be included in the planning from the outset. This allows for consideration of cable routing and available space in the installation room right from the beginning.

Heating elements, power managers and solar modules in the product range

PVundSO offers a wide selection of products for its PV heating elements, covering various power ranges. In addition to the heating elements themselves, the product range includes power managers, measuring equipment, and compatible hot water storage tanks from TESY. The my-PV screw-in heating elements are designed for the AC-THOR system and are available in 3 kW and 9 kW versions. The 3 kW model is also compatible with the SOL-THOR. The SOL-THOR offers stepless heating output control up to 3.600 watts and can handle 1 to 10 modules, making it suitable even for small systems the size of a balcony power plant.

Why does a photovoltaic heating element need its own controller? Only a controller ensures that it uses only excess electricity for heating. With my-PV's screw-in heating elements, this is handled by the AC-THOR or SOL-THOR models. The DC ELWA solar heating element, on the other hand, already has its own integrated controller. Additionally, there is a temperature sensor for the AC-THOR that reports the storage temperature to the controller. All other devices from this manufacturer are listed on the my-PV heating element page.

PVundSO delivers larger packages via freight carrier; shipping is free for orders over €899. Package deliveries are free throughout Germany for orders over €100. Experienced electrical engineers are available for personal consultation at our Hildesheim location, where you can also pick up your order. Beforehand, use our PV system checklist to assess your roof, storage, and energy consumption for your planned photovoltaic system.

Frequently asked questions about photovoltaics with heating element

How much solar power does a heating element for hot water require?

A 300-liter storage tank that needs to be heated by 40 degrees Celsius requires approximately 14 kWh. Even a photovoltaic system with a capacity of around 4 kWp can supply this amount on clear days between April and September, in addition to the household's own consumption. The actual amount that remains depends on how much electricity your household uses during the day.

Can a PV heating element be installed in any hot water storage tank?

A PV heating element fits most hot water storage tanks because they have a 1,5-inch threaded connection. Also check that there is enough space inside the tank for the length of the heating element. Older tanks without a suitable connection require a flange adapter or must be replaced with a newer model, such as the 200-liter TESY tank from our product range.

What is the payback period for a PV system with a heating element?

For a PV system with an immersion heater, the payback period depends primarily on which energy source the solar power replaces. If it replaces gas, a complete system usually pays for itself in around 6 to 8 years, while a single immersion heater with a controller on existing modules pays for itself much faster.

Switching from an electric boiler is even faster, because every kilowatt-hour you use yourself saves you the full cost of the electricity. You can calculate the payback period in advance based on your consumption and electricity costs.