Heating bills in Germany are climbing. The war in Ukraine and the subsequent cutoff of Russian gas supplies have driven up the cost of gas and electricity significantly. Households are feeling the pinch. The desire to save money while keeping warm is at an all-time high.
One solution appears to be switching to a Wärmepumpe. These systems promise to be cheaper and more environmentally friendly than traditional oil or gas boilers. But what do these devices actually do?
How Wärmepumpen Extract Heat from Cold Air
A Wärmepumpe pulls heat from the environment. It uses air, ground, or groundwater to heat or cool a home. In new constructions, this is now the most common heating method. It is considered efficient and climate-friendly, even though it requires electricity to run.
The technology relies on temperature differences. It exploits the gap between the outside temperature and the indoor temperature, or between the soil and the surface. The extracted heat must be raised to a usable level through a cycle. A refrigerant acts as the transport medium. It goes through four specific steps: evaporation, compression, condensation, and expansion.
- Evaporation: The refrigerant evaporates at the outside ambient temperature. Since winter temperatures can drop below zero, the refrigerant must have a very low boiling point.
- Compression: An electrically driven compressor compresses the refrigerant vapor. This increases both the pressure and the temperature. The resulting temperature is significantly higher than the indoor temperature of the building.
- Condensation: The heated, compressed vapor releases heat into the heating water via a heat exchanger. The water heats up enough to serve as a heating medium or hot water. The refrigerant condenses into a liquid but remains under high pressure.
- Expansion: The liquid refrigerant passes through an expansion valve. This reduces the pressure to its original level, allowing the cycle to repeat.
The Efficiency Advantage
The clever part is the ratio of energy sources. Under normal circumstances, about eighty percent of the heating energy comes from free environmental heat during evaporation. The electricity required for the cycle contributes only twenty percent.
Heating with outside air in winter seems counterintuitive. Yet, the Wärmepumpe principle makes it possible. The system moves heat rather than creating it from scratch. This distinction matters for your wallet and the planet.
The core principle: 80% free ambient heat, 20% electricity.
This efficiency is why the technology is gaining traction despite the initial installation costs. It transforms a seasonal problem—lack of warmth—into a solvable mechanical process. The question now is whether the upfront investment pays off over the lifespan of the unit. That calculation depends on local electricity prices and the specific insulation of your home. There is no one-size-fits-all answer. But the mechanics of the Wärmepumpe remain consistent. It works by manipulating pressure and phase changes to move heat where it is needed.
How Heat Pump Types Affect Your Home’s Efficiency
There are essentially three main contenders in the race to heat your home efficiently: air-source, ground-source, and water-source heat pumps. Each has its own quirks. Each has its own set of rules. You can’t just pick the one that looks cheapest on Amazon. The reality is messier.
Air-source heat pumps are the most common for a reason. They are simple. They are straightforward. These units pull thermal energy from the outside air using fans. Think of it like a reverse air conditioner. Installing them is relatively easy. You need an outdoor unit and an indoor fan coil. But simplicity comes with a tax. In winter, efficiency drops. Why? Because the air gets cold. Fast.
When the outside temperature plummets, the temperature gap between your warm indoors and freezing outdoors widens. The electric compressor has to work harder. It burns more electricity to bridge that gap. The colder it is, the less efficient the system becomes. It’s basic physics. You are fighting the environment.
Groundwater heat pumps are different. They are widely considered the most efficient type available. They use groundwater as their heat source. And groundwater is stable. Even in the dead of winter, it rarely drops below ten degrees Celsius. That’s warm compared to freezing air. The heat pump doesn’t have to work nearly as hard.
But here is the catch. You can’t just install one anywhere. Homeowners must drill two wells. Two. And they need permits. Lots of permits. Local authorities have to approve the extraction. The chemical composition of the water matters too. If the water is too corrosive or mineral-heavy, the system can suffer. Not every property has access to suitable groundwater. If you don’t have it, this option is off the table.
Ground-source heat pumps operate similarly in principle but draw energy from the earth itself. The soil holds heat better than air does. It stays relatively constant year-round. This makes them highly efficient too. You have two choices here. You can drill deep boreholes. Or you can lay out large, shallow pipes across a wide area of land. Both require digging. Both require permission.
Drilling is restricted in many areas. Zoning laws vary wildly. You might find the perfect spot on paper only to be told by the local council that you can’t touch the subsurface. It’s a bureaucratic hurdle. It adds time and cost to the project before a single pipe is laid.
This brings us to the hard truth. Not every heat pump works in every location. Geography dictates your options. If the soil is rocky, drilling is expensive. If the water table is too low or polluted, groundwater pumps fail. If you live in a dense urban area with no yard space, you might be forced into an air-source model despite the winter inefficiency.
Beyond the type of pump, the house itself matters. A heat pump is only as good as the building it serves. You need good insulation. Without it, you are heating the outdoors. The heating system inside also plays a role. Heat pumps work best with low-temperature distribution. That means large radiators or, ideally, underfloor heating. Small, old-fashioned radiators might not handle the lower flow temperatures efficiently. You might end up with a cold house and a high bill.
So, which path do you take? There is no universal winner. The
It’s not black and white. Whether a heat pump is truly eco-friendly depends entirely on the specific unit. Even though three-quarters of its heating energy comes from renewable sources like air, water, or ground, the system still needs electricity. That powers the compressor and pumps. And that electricity often still comes from coal plants rather than wind or solar.
So what about the second selling point? The money.
Saving cash is possible. But it’s not instant. Buying and installing the unit costs tens of thousands of euros upfront. For an air-source heat pump, you’re looking at between 20,000 and 25,000 euros. You can apply for state subsidies to cover some of that, but you still need to front the bulk of the cash.
Look at running costs only and the picture changes. If you already have the system, you save significantly compared to oil and gas. The comparison portal Verivox analyzed this. Heating with an efficient heat pump costs 39% less on average than gas. Even a less efficient model saves you 11%. Maintenance is lower too. Expect about 100 euros a year plus labor and travel fees for technicians.
It’s cheaper over time. But the barrier to entry is high. Homeowners must pay big sums first.
