Heating with Solar Electricity: Underfloor Heating Without Conventional Radiators

People living through recent winters in Central Europe will recognise the issue: homes cool down noticeably, conventional radiators run at full capacity, yet bills keep rising. The energy crisis, pressure to cut CO₂, and ageing gas boilers are making many households uneasy. At the same time, an approach is emerging that feels like a quiet, small-scale revolution: heating with solar electricity, directly through the floor, with no conventional radiators at all.

Heating without radiators – what does it involve?

The basic idea sounds almost too straightforward: electricity from photovoltaic systems on roofs or façades powers a heating solution that does not require visible radiators. Heat usually comes up through the floor, either via electric heating mats or a water-based system operated by a heat pump.

Rather than warming a room in isolated spots with individual radiators, heat is spread over a broad area. The floor becomes the effective heating surface, while the photovoltaic system is there to supply as much of the required energy as possible.

"The combination of photovoltaics and surface heating turns the sun into a direct supplier of heat – with virtually no ongoing costs."

At its heart, this approach shifts the emphasis away from fossil fuels such as gas and oil towards self-generated green electricity. Anyone with enough roof space and a well-insulated flat or house can obtain a substantial proportion of their heating energy from their own system.

How “heating with the sun” works day to day

Photovoltaic panels convert sunlight into electricity. That electricity can be used in three ways:

• directly for electric underfloor heating or infrared panels;
• to power a heat pump that heats water for a surface-heating system;
• or alongside a battery storage system that retains energy for the evening and overnight.

Heat pumps in particular have a key role here. They use solar electricity to raise ambient heat from the air, ground or groundwater to a usable temperature. In ideal conditions, one unit of electricity produces three to four units of heat.

Why the floor becomes the centre of the heating system

A core feature of these newer heating concepts is surface heating installed in the floor. The physics are simple: warm air rises. When heat is delivered from below and distributed over a large area, a room can often feel comfortable at a lower air temperature.

This allows lower flow temperatures, meaning less energy is needed for the same level of comfort. It also removes intrusive radiators from walls, which is particularly welcome to architects and interior designers.

"Underfloor heating uses large surfaces at low temperatures, making it a perfect match for renewable energy sources such as solar electricity and heat pumps."

Benefits: where solar heating outperforms conventional radiators

Switching to this type of system can bring advantages in several areas. The main benefits include:

• Significantly lower energy costs: Once the system has paid for itself, ongoing costs are low. A large share of the heat comes “free” from the sun.
• Independence from gas and oil: No price shocks on the gas market, less dependence on imports, and no more oil deliveries.
• No local emissions: Neither soot nor exhaust gases are produced in the home. This improves air quality in living spaces and towns and cities.
• A pleasant indoor climate: Underfloor heating creates even, gentle warmth. Cold corners and overheated areas occur less frequently.
• Less circulating dust: Without hot radiators creating air currents, less dust is moved around rooms – a benefit for allergy sufferers.

Many users say rooms with underfloor heating already feel cosy at 20 to 21 degrees, whereas conventional radiator systems are often set to 22 or 23 degrees. That modest difference saves energy without reducing comfort.

What does it cost – and when does it pay for itself?

The main obstacle comes at the start: purchasing and installation costs. A photovoltaic system, inverter, potentially a battery, heat pump and underfloor heating can quickly add up to a five-figure sum. When refurbishing an older building, floors may also need to be opened up and insulation improved.

At the same time, solar technology has been becoming cheaper for years. In many areas, government support schemes and low-interest loans cover part of the investment. Illustrative calculations show that well-planned installations can reduce heating and electricity demand sufficiently for the system to pay for itself after several years.

Aspect	Conventional heating (gas/oil)	Solar-based surface heating
Ongoing costs	high, dependent on global market prices	low, mainly maintenance
CO₂ emissions during operation	significant	close to zero with green electricity
Visible radiators	yes	no
Sense of comfort	localised heat	even radiant heat

Who can genuinely benefit from switching?

The technology is not equally suitable for every building. Several conditions should be met for the system to operate economically and effectively:

• sufficient roof or façade area with good sunlight exposure;
• the best possible thermal insulation for façades, roofs and windows;
• low flow temperatures, typically through underfloor or wall heating;
• electrical infrastructure designed to handle higher loads.

In poorly insulated older properties with outdated windows and numerous thermal bridges, creating an efficient system remains difficult even with solar power and a heat pump. In such cases, substantial refurbishment is often unavoidable before changing the heating system becomes worthwhile.

Technical challenges and potential pitfalls

Although the concept sounds promising for the future, it does not run itself. Anyone planning too tightly may face unpleasant surprises in the depths of winter. Typical problems include:

• an undersized photovoltaic area;
• no storage system, or one that is too small;
• an inadequately specified heat pump that relies solely on an electric immersion heater in freezing conditions;
• poor control of electricity generation, heating and storage.

The essential factor is an integrated plan. Energy advisers and specialist installers now often design the whole building as one system: insulation, heating technology, solar area, storage and user behaviour all work together. The better this interaction functions, the closer homeowners come to heating largely with their own solar energy.

Practical examples from everyday life

In many new-build developments, houses can now be seen with photovoltaic panels covering almost their entire roofs. A heat pump hums in the utility room, while heating pipes sit within the screed on the ground floor. During the day, the system generates more electricity than the house currently needs; the surplus charges the battery or is fed into the grid.

At night, the battery then covers part of the demand. If that is not enough, the electricity grid supplies the remainder. Even so, annual electricity bills often remain surprisingly low in well-planned projects, because high summer surpluses improve the overall balance.

"Anyone who considers heating, insulation and solar electricity together can run their home with self-generated energy for almost the whole year."

Key terms explained briefly

Photovoltaics (PV): Technology that converts sunlight directly into electricity. It is based on solar cells made from semiconductor material, usually silicon.

Heat pump: A device that raises ambient heat to a higher temperature level, much like a refrigerator operating in reverse. One unit of electricity can generate several units of heat.

Surface heating: A heating system in which large areas, such as floors or walls, are heated instead of small radiators. This means the heating surface can operate at a lower temperature.

How the trend could develop further

Photovoltaic panels are becoming slightly more efficient and less expensive each year. At the same time, many countries are accelerating the move away from fossil-fuel heating systems. This creates pressure for homeowners, but also an opportunity: those already planning a modernisation can take the step towards a heating system that offers considerably fewer dependencies over the long term.

Combinations are also becoming increasingly interesting: solar thermal systems for direct hot-water production, photovoltaics for the heat pump and household electricity, and intelligent controls that incorporate weather data. The aim is a home that ideally produces a large share of its own energy – and where radiators truly become unnecessary.