Heating Systems Study: Air-to-Water Heat Pump with Photovoltaics Comes First

A comprehensive study by the Technical University of Munich has settled the debate over which heating system is best. Researchers examined 13 different systems, assessing both their economic profitability and their environmental impact. The findings challenge several widely held assumptions.

With energy prices soaring and environmental concerns increasing, selecting the right heating system has become essential. Homeowners can easily feel overwhelmed by the range of options on the market: heat pumps, pellet stoves, gas systems and more. Every installer promotes the benefits of their own solution. But what does the evidence actually show? In a study published in 2024, a team of German researchers provides clear answers founded on scientific data.

A robust methodology that shifts the debate

The scientists took a thorough approach. To produce dependable findings, they modelled the operation of 13 different heating systems in a typical two-storey house. Their innovative method combines life-cycle assessment (LCA), used to measure environmental impact, with net present value (NPV), used to assess economic viability. This two-part evaluation makes it possible to identify the options that genuinely perform well across every criterion.

The team included every relevant factor: installation costs, energy use, maintenance expenses, CO2 emissions and the use of natural resources. Their calculations also accounted for likely changes in energy prices and future developments in Germany’s electricity mix.

The air-to-water heat pump with photovoltaics takes top place

The results are unequivocal: the air-to-water heat pump combined with photovoltaic panels ranks first for eco-efficiency. Compared with the reference system, a gas boiler, it has an environmental impact that is 17% lower while cutting costs by 6%. Even under the least favourable scenario considered by the researchers, this option remains more effective than many alternatives.

Several factors explain the strong results delivered by this combination. First, an air-to-water heat pump makes efficient use of energy available in the outside air. Secondly, adding photovoltaic panels substantially reduces both the electricity bill and the system’s carbon footprint. The researchers also note that improving photovoltaic self-consumption could enhance these outcomes further.

Unexpected results in the heating-system ranking

The wood gasification boiler performs surprisingly well, taking second place for eco-efficiency. Its environmental impact is 42% lower than that of a gas boiler, despite costing 20% more. This positive result is partly due to wood being treated as a renewable resource, provided it comes from sustainably managed forests.

By contrast, some systems regarded as environmentally friendly prove disappointing. The pellet boiler combined with solar thermal technology and the heat pump with an ice storage unit show the weakest eco-efficiency performance. According to the researchers, the complexity and high cost of these systems do not offset their environmental benefits.

Although economical to operate, the gas boiler is held back by its significant environmental impact. It produces the highest greenhouse-gas emissions of all the systems assessed, including when it is paired with solar thermal panels.