Hot Water Heat Pump - Nerja
Aerothermal hot water heat pump replacing a gas water heater in a Nerja villa — COP 3.0+ sanitary hot water with Legionella pasteurisation at 60°C, complying with Spain's 2022 CTE thermal regulations.
By Ben Hayden
Project Overview
The Challenge
The family home in Nerja was spending €85–€110 per month on hot water alone — a 200-litre electric immersion cylinder running at a constant 60°C drew over 3kWh daily and was responsible for nearly 40% of total household electricity use. The family had already switched to solar panels for daytime electricity but the immersion heater's timing did not align with solar generation peak — it ran overnight on expensive grid electricity. The challenge was to find a replacement that would align hot water heating with solar surplus and reduce consumption by at least 60%, without the cost or complexity of relocating the existing cylinder installation.
The Solution
300L heat pump water heater replacing electric resistance system. Significant energy savings for family home.
Technical Specifications
- 300L heat pump water cylinder
- COP 3.5 efficiency rating
- Smart temperature control
- Backup heating element
- Insulated installation
Our Installation Process
Hot Water Demand & Solar Surplus Audit
We analysed 6 months of solar generation data alongside electricity billing data to quantify the mismatch between solar surplus and immersion heater timing. Solar generation peaked at 11:00–15:00; the scheduled immersion run was 01:00–04:00 (cheap-rate timer setting). By simply installing the thermodynamic heat pump and scheduling it to run during solar peak hours, 70–80% of hot water demand can be covered by solar surplus at zero incremental cost.
Thermodynamic Heat Pump Selection & Cylinder Integration
The Daikin Altherma Monobloc DHW unit was specified — a compact air-to-water heat pump that uses the existing 200-litre cylinder without requiring replacement. The unit is plumbed in series with the existing cylinder and provides the primary heat source (COP 3.5), with the existing immersion element retained as a backup for extended cold or cloudy periods. Installation was completed in 4 hours with no structural changes to the utility room.
Smart Scheduling & Commissioning
The heat pump controller was programmed to prioritise solar surplus hours (10:00–16:00) with a secondary run schedule at 06:00 for morning peak demand. Legionella protection was set to run the backup immersion element to 65°C once per week, as required by Spanish sanitary regulations for thermostatic water heaters. The client was provided with the Daikin online controller app for remote temperature and schedule management.
Refrigerant Certificate & Documentation Handover
All refrigerant handling was completed by our qualified engineers (EU Regulation 517/2014). A full refrigerant equipment record was issued: refrigerant type (R290 — propane, zero GWP), charge weight, unit serial number, and engineer certification number. The Daikin warranty was registered in the client's name, and the REBT electrical compliance certificate (Boletín Eléctrico) was submitted to the Delegación de Industria de Andalucía within the required 5-day window. The client received a laminated commissioning data card showing the set point schedule, Legionella cycle setting, and solar priority window for future reference.
Results
See the installation scope and equipment below; no financial outcome is promised.
Backed by Research
References for checking the proposed design. These sources do not certify this project's performance, savings, eligibility or commissioning records.
Plan hot water around demand and safe operation
Check storage size, recovery time, installation location, heat-pump performance and any supplementary heating. Hygiene controls must follow the applicable building use and equipment instructions; an energy-saving setting must not compromise safe water operation.
BOE — RITE: applicable thermal-installation requirements ↗Frequently Asked Questions
Related Services
LIT services in Nerja directly related to this work.
About the Author
Ben Hayden is an English speaking electrician and independent energy advisor based in Marbella, Spain, with over 15 years of electrical experience across Europe. He provides independent energy and electrical checks for overseas property owners and managers across the Costa del Sol — helping clients cut electricity bills, navigate Spanish regulations, and make confident decisions on solar PV, heat pump, EV charger and battery storage projects. Ben advises in plain English on projects where the paperwork is in Spanish and the stakes are high. His writing has appeared in ExpatArrivals, The Olive Press, Euro Weekly News, BuildingTalk and pv magazine.
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Enquire with Agua ThermProject Details
- Location
- Nerja, Málaga
- Completed
- November 2025
- Service
- Hot Water
- Author
- Ben Hayden