Heating bathroom water accounts for between 25% and 35% of the average Spanish household’s energy consumption. That means for every EUR 100 you pay in energy bills, EUR 25 to 35 literally go down the drain as hot water. At Bathscape we’re convinced that a bathroom renovation is the perfect moment to rethink how you heat that water. And aerothermal technology, right now, is the smartest answer from both a technical and economic standpoint.
What Aerothermal Energy Is and How It Works
Aerothermal energy is essentially a heat pump that extracts thermal energy from outdoor air and transfers it to water. It doesn’t generate heat through combustion (like a gas boiler) or through electrical resistance (like an electric water heater). It moves heat from one place to another, and that makes it radically more efficient.
The key parameter is the COP (Coefficient of Performance). A COP of 3 means that for every kWh of electricity consumed, the system produces 3 kWh of heat. Put more clearly: you get three times more energy than you pay for.
Current aerothermal DHW (Domestic Hot Water) units have a COP between 3 and 4.5, depending on the outdoor temperature. And here’s where the differential advantage of living in Valencia comes in.
The Valencia Advantage: Climate and COP
A heat pump’s COP increases when the outdoor temperature is higher, because more thermal energy is available in the air. In Finland, at -20 C in winter, the COP drops to 2 or less. In Valencia, with average winter temperatures of 8-12 C and summer above 25 C, the annual average COP sits between 3.5 and 4.2.
According to data from IDAE (Institute for Energy Diversification and Saving), Valencia’s climate zone (B3) is one of the most favourable in Spain for aerothermal, with a seasonal average performance (SCOP) 15-20% higher than the central plateau.
This isn’t a minor nuance. It means that in Valencia aerothermal is even more cost-effective than the national average, and the national average is already good.
Comparison: Gas vs Electric vs Aerothermal
Let’s get to the numbers. We calculate the annual DHW cost for a family of 4 with average consumption of 200 litres/day at 45 C:
Gas Boiler
- Efficiency: 90-95%
- Consumption: ~2,800 kWh/year of gas
- Natural gas cost (Spain average): EUR 0.075/kWh
- Annual cost: EUR 210-250
- Add: mandatory maintenance (EUR 80-120/year), gas inspection, equipment amortisation
Electric Water Heater
- Efficiency: 95-100% (COP = 1)
- Consumption: ~2,700 kWh/year of electricity
- Electricity cost (2.0TD tariff): EUR 0.18/kWh
- Annual cost: EUR 480-540
- No mandatory maintenance
Aerothermal (DHW Heat Pump)
- Average COP Valencia: 3.5
- Consumption: ~2,700 / 3.5 = 770 kWh/year of electricity
- Electricity cost: EUR 0.18/kWh
- Annual cost: EUR 135-160
- Minimal maintenance (filters every 2 years)
The difference is telling. Aerothermal consumes 60-70% less energy than an electric water heater and 35-45% less than a gas boiler. And if you add a photovoltaic installation (increasingly common in Valencia homes), the cost approaches zero.
Types of DHW Units
Compact Heat Pump (Monobloc)
A single unit integrating compressor, heat exchanger, and water tank (150-300 litres). Installed inside the home, in a garage, storage room, or laundry. It needs air inlet and outlet (160-200 mm ducts to the outside or a ventilated space).
Price: EUR 2,000-4,000 (unit + installation).
This is the most common option for detached houses or flats with a storage room.
Split Heat Pump
Similar to an air conditioner: outdoor unit (compressor) + indoor unit (tank). Allows the outdoor unit to be installed on a terrace or facade and the tank inside the home.
Price: EUR 3,000-5,500 (unit + installation).
Ideal for flats without indoor space but with a terrace or balcony.
Air-to-Water Heat Pump (Centralised System)
Larger units covering DHW and heating/cooling. Brands like Daikin Altherma, Vaillant aroTHERM, or Mitsubishi Ecodan. These are the complete solution for detached houses, but their sizing exceeds the scope of a bathroom renovation.
Price: EUR 6,000-12,000 (unit + full installation).
The Perfect Moment: The Bathroom Renovation
This is something we repeat constantly at Bathscape: if you’re doing a full bathroom renovation, it’s the ideal moment to install aerothermal. For several reasons:
The plumbing is already open: Hot water pipes are accessible, facilitating connection of the new system without additional building work.
It can be sized for the new bathroom: If you’re switching from bathtub to shower, hot water consumption changes. If you install a shower with a digital thermostat, the flow rate is different. This data allows the heat pump to be correctly sized.
Active subsidies: The Recovery Plan and EU Next Generation funds include grants of EUR 1,000-3,000 for aerothermal installation in existing homes. These grants are processed at the same time as the renovation, simplifying bureaucracy. More on energy efficiency in renovations.
Gas boiler elimination: If your gas boiler is at end of life (over 15 years), replacing it with aerothermal during the bathroom renovation is logical. You eliminate a piece of equipment, its mandatory inspections, and its associated risk.
Compatibility with Underfloor Heating
Aerothermal and underfloor heating are complementary technologies that enhance each other. An air-to-water heat pump can supply both DHW and a low-temperature hydronic underfloor circuit (30-40 C), which is exactly the range where aerothermal has the highest COP.
In bathrooms, hydronic underfloor heating (powered by aerothermal) is an alternative to the electric option we’ve covered in previous articles. The initial investment is higher but the operating cost is significantly lower in the long term.
The combination of aerothermal + hydronic underfloor heating + smart design is what we at Bathscape consider the efficiency trident for a 2026 bathroom.
Sizing: What Size Do You Need
Correct sizing is the difference between an efficient system and one that falls short or oversizes and wastes energy. Key factors:
Number of people: The base demand. Rule of thumb: 50 litres/person/day at 45 C.
Number of bathrooms: Each additional bathroom doesn’t add linearly (they’re not all used simultaneously), but does require a larger tank to cover peak demand.
Simultaneity: If two people shower at the same time (en-suite bathrooms, for example), the instantaneous flow rate must be sufficient.
| Home | Recommended tank | Heat pump output |
|---|---|---|
| 1-2 people, 1 bathroom | 150 litres | 1.5-2 kW |
| 3-4 people, 1-2 bathrooms | 200-250 litres | 2-3 kW |
| 4-6 people, 2-3 bathrooms | 250-300 litres | 3-4 kW |
A common mistake is undersizing the tank to save on the purchase. The result: water runs cold during long showers and the system activates an emergency electric resistance element, eliminating all savings. At Bathscape we always size with a 15-20% margin.
Installation Cost and Payback
Cost breakdown for the most common option (200L compact heat pump) in a Valencia home:
| Item | Cost |
|---|---|
| Unit (heat pump + 200L tank) | EUR 2,000-3,000 |
| Hydraulic installation | EUR 400-700 |
| Electrical installation | EUR 200-400 |
| Air ducts | EUR 150-300 |
| Old boiler removal | EUR 100-200 |
| Gross total | EUR 2,850-4,600 |
| Estimated subsidy | -EUR 1,000 to -2,500 |
| Net total | EUR 1,350-3,100 |
Payback
If replacing an electric water heater, you save around EUR 350-400/year. The net payback (after subsidy) is 3-5 years.
If replacing a gas boiler, you save around EUR 100-150/year in energy but eliminate the EUR 80-120/year in mandatory maintenance. The net payback is 4-7 years.
According to the CTE, Basic Document HE4 actively promotes incorporating renewable sources (including aerothermal) for DHW production, reinforcing the trend towards this technology in new builds and renovations.
Aerothermal and the Future of Bathroom Hot Water
The trend is irreversible. European regulations will progressively ban gas boilers in new builds (already happening in several countries) and incentivise efficient electrification. Aerothermal is the bridge technology between the combustion heating model and a 100% renewable electric future.
In Valencia, with 2,660 hours of sunshine per year and mild winter temperatures, the aerothermal + photovoltaic combination turns the bathroom into a near-zero energy consumption zone. And when integrated with home automation and intelligent consumption control, the data we’ve seen in our Bathscape projects is frankly encouraging.
From Bathscape’s perspective, any full bathroom renovation should at least evaluate aerothermal installation. It won’t always be the chosen option — there are cases where the building’s infrastructure doesn’t allow it, or where the budget is too tight — but dismissing it without analysis means missing an opportunity that becomes more obvious with every passing year.
Frequently Asked Questions
Can aerothermal be installed in a flat without a terrace?
Yes, with a monobloc unit placed in a storage room, laundry, or garage. It needs intake and exhaust air ducts to the outside (160-200 mm diameter). If there’s no space for ducts, a split unit with the outdoor section on the facade can be installed, subject to residents’ association approval.
Does aerothermal work in winter in Valencia?
Perfectly. With minimum temperatures of 3-5 C on the coldest nights (and only for a few weeks a year), the COP stays above 2.5. The system only loses significant efficiency below -5 C, which in the Valencia area is extremely rare. See more on bathroom energy savings.
How noisy is a heat pump?
Current units generate between 35 and 50 dB(A), equivalent to a quiet conversation or a refrigerator. Premium models with inverter compressors are particularly quiet. It’s important not to place the unit next to a bedroom if it’s a monobloc.
Can I connect aerothermal to my solar installation?
Yes, and it’s the ideal combination. Photovoltaic panels produce the most electricity at midday, which is when the heat pump can heat the tank using solar-rate power. With a 200-300 litre tank and good programming, it’s possible to cover 60-80% of DHW with solar energy. More on efficiency in our project configurator.
Want to take advantage of your renovation to install aerothermal? At Bathscape we coordinate the bathroom renovation with the DHW system installation to optimise costs and timelines. Configure your project and receive an integrated plan.