The fothermo 1 kW solar heating element can reduce hot water costs by up to 75 percent – without an inverter or complicated installation. This article explains how photovoltaic hot water preparation works, what cost and energy savings are possible, and why the investment pays for itself in just a few years .
Energy prices have been rising steadily for years, and hot water preparation in particular.
Hot water is a significant cost factor in many households. Around 10 to 20 percent of total energy consumption is attributable to hot water alone – this adds up noticeably on the annual bill.
More and more homeowners and renovators are therefore looking for an efficient and sustainable way to reduce their hot water costs and become more independent from rising energy prices.
The fothermo 1 kW solar heating element offers a particularly simple and economical solution. It uses the generated photovoltaic electricity directly , without conversion losses and without an inverter , to heat water in the existing hot water storage tank.
But is it really worth buying? And how quickly does a solar immersion heater pay for itself? This article explains how it works , the cost-benefit analysis , and the amortization of the 1 kW model – and shows how you can permanently reduce your energy costs with photovoltaic hot water .
The fothermo solar heating element is an electric heating system that is powered directly by direct current (DC) from photovoltaic modules . It works like a classic immersion heater that is screwed into the hot water storage tank .
Unlike conventional systems that first convert solar power into alternating current (AC) and then use it via the house's electrical system, the solar heating element uses the generated photovoltaic power directly for hot water preparation . This eliminates conversion losses – the energy is used efficiently where it is needed.
The system is simple: PV modules generate electricity, which is then transmitted via DC cables to the heating element that heats the water. Because the system operates at low voltage (below 50 volts) , installation is minimal and it is ideally suited for existing systems.
A major advantage of the fothermo system is its plug-and-play installation . In many cases, the solar heating element can be installed independently – without an installer, without complex modifications, and without red tape . Because the heating element operates off-grid, no registration or permits are required. This saves not only time but also installation costs, significantly increasing the system's efficiency and amortization .
Furthermore, the device can be integrated into almost any existing hot water storage tank with a 1½-inch thread . Storage capacities up to approximately 500 liters can be easily accommodated. If required, the system can be expanded with an intelligent surplus function , allowing excess photovoltaic power to be fed into the home grid via a micro-inverter .
The crucial question is: How much can energy costs really be reduced with a solar heating element – and when does the investment pay off?
Practical experience and real-world measurements show that a solar heating element can save up to 75 percent on hot water costs . This is due to its efficiency: the solar heating element uses the free solar energy available throughout the day to produce hot water.
In Germany , photovoltaic radiation is strong enough from about April to October to cover almost all of the hot water needs of a two-person household with solar power . During this time, the gas, oil, or heat pump heating system hardly needs to operate. This not only significantly reduces energy consumption but also extends the lifespan of the heating system.
existing heating system.
A typical two-person household spends around €300 annually on hot water. Depending on the type of hot water system, the absolute costs can vary slightly depending on the technology (oil or gas heating, heat pump, electric direct heating). If the fothermo solar heating element covers 75 percent of these costs, the expenses drop to around €75 per year . This translates to annual savings of approximately €225 .
With an investment of around €1,000 (including heating element, PV modules, cabling and mounting system), the payback period is approximately 4 years . In households with higher hot water demand, the payback period is correspondingly shorter.
Tip: Calculate your personal savings directly with the fothermo savings calculator . Enter your consumption, number of modules and storage size – and see immediately how quickly your solar heating element will pay for itself.
The question of whether energy costs can be "halved" can therefore be answered clearly: Yes – this is possible with regard to hot water costs. Since hot water makes up a large part of total energy costs, this saving has a significant impact on the annual budget.
The fothermo solar heating element can be easily integrated into existing hot water systems in most cases. A storage tank with a 1½-inch connection thread is required, which is already present in most households.
1. Empty the storage tank: Before installation, the hot water storage tank is emptied so that the heating element can be safely mounted.
2. Remove the old heating element or use a free opening.
3. Screw in the new solar heating element and refill the storage tank.
4. Connecting PV modules: The modules are usually connected in parallel to achieve the optimal voltage of approximately 38 – 43 volts DC .
5. Set the temperature – done! Once everything is connected, the system works independently with photovoltaic hot water .
Since the heating element operates at low voltage (below 50 volts) , installation is easily manageable for many technically skilled users. However, basic electrical safety regulations should still be observed – especially regarding cable cross-section and fuse rating .
The fothermo system is designed for easy self-installation . It can be installed without a specialist company, thus saving time and installation costs and increasing overall cost-effectiveness .
Optionally, the system can be expanded to include an intelligent surplus function : Excess solar power is fed into the home grid via a micro-inverter – ideal for anyone who wants to optimize their self-consumption .
Users of the fothermo solar heating element benefit in multiple ways – both financially and ecologically. Heating water with photovoltaics is one of the most efficient ways to reduce energy costs and optimally utilize one's own electricity production.
While feed-in to the grid yields only meager returns, direct self-consumption of solar power is significantly more worthwhile. Every kilowatt-hour that doesn't have to be purchased at high prices or generated using gas or oil saves real money.
The solar heating element uses excess photovoltaic electricity directly in the household – without conversion losses, without inverters, and without red tape . This makes hot water preparation almost self-sufficient , and the generated electricity is used where it is most beneficial: in your own home.
The solar heating element operates emission-free and actively contributes to CO₂ reduction . Since the generated solar power is converted directly into heat , there are no losses from intermediate steps. This makes the fothermo solar heating element one of the most environmentally friendly solutions for hot water preparation using photovoltaics .
It is also ideally suited for existing buildings : thanks to simple retrofitting, no complex installation or structural alterations are necessary. The system can be integrated into existing hot water storage tanks at any time – quickly, flexibly, and cost-effectively .
The combination of a heat pump and a solar heating element is particularly interesting. While heat pumps operate less efficiently at high temperatures, the solar heating element takes over precisely this range:
It heats the domestic hot water with solar-generated electricity , thus relieving the heat pump. This leads to significantly higher energy savings , reduces wear and tear on the heating system , and extends its lifespan .
The fothermo 1 kW solar heating element is an economically attractive and sustainable solution for anyone who wants to reduce their hot water costs and become more independent from rising energy prices.
By directly using photovoltaic electricity, the water is heated efficiently – without an inverter, without energy losses . At the same time, the system relieves the existing heating system, as it has to work significantly less over many months.
The ease of retrofitting makes the solar heating element particularly attractive for existing buildings , as no major renovations or additional technology are required.
Under realistic conditions , up to 50% or more of the
Save on hot water costs .
With a payback period of two to five years, it is clear:
The solar heating element is an investment that quickly pays for itself – and ensures significantly lower energy costs in the long term.
👉 Tip: Supplement your hot water storage tank now with the fothermo 1 kW solar heating element and make optimal use of your photovoltaic electricity – simply, efficiently and without bureaucracy.
For the fothermo solar heating element to work, your hot water storage tank should have a 1.5-inch thread – this is already present on most standard tanks. A volume of up to approximately 500 liters is ideal. Photovoltaic modules that supply direct current (DC) are also required. This allows the water to be heated directly with solar power – without an inverter and without energy losses.
For the fothermo 1 kW solar heating element, 3 to 4 photovoltaic modules with a power output of 400 to 500 Wp each are generally recommended. This allows the system to achieve the ideal voltage of 38 to 43 volts DC for efficient hot water production. This size is optimal for both single-family homes and balcony power plants if you want to use solar power directly.
Yes – the fothermo solar heating element works completely without an inverter , as it uses direct current (DC) directly from the PV modules. This allows it to be easily connected to a balcony power plant that operates on a DC basis. The advantages: no grid feed-in, no registration with the grid operator, and no red tape. The solar power is used directly and efficiently for hot water preparation.
As long as the solar heating element operates in off-grid mode , meaning it doesn't feed into the public grid , no registration or permit is required . The system works independently and uses solar power directly. Only when a micro-inverter is connected to feed excess electricity into the home's electrical system do the usual registration requirements apply – similar to a balcony power plant.
The payback period depends on individual consumption, solar irradiance, and electricity prices. In practice, it usually lasts between 2 and 5 years . A typical two-person household can save around €225 annually if approximately 75% of its hot water costs are covered by photovoltaic hot water heating . After this period, the solar heating element continues to operate virtually free of charge – using clean energy directly from the sun.
Tip: Use the fothermo savings calculator to determine your personal amortization period and annual costs .
Calculate your savings individually. The tool shows you immediately how much you can save by using your solar heating element with photovoltaics .
