Domakihub Install a Solar Water Heater and Cut Your Energy Bills
A practical guide to fitting a solar thermal system on any home, rental, or hotel in Greece.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 5 min read
Greece's 300-plus sunny days a year make solar water heating one of the smartest upgrades you can make to a home, holiday rental, or hotel. The video above from This Old House walks through the full installation on a real property; the steps below translate that process into a clear checklist sized for the Greek context, including rooftop mounting on flat terraces and tile roofs. Follow this guide and you can realistically cover 70–80 percent of your annual hot-water demand with free energy from the sun.
Why solar water heaters are a natural fit for Greece
Greece has among the highest solar irradiance in Europe, with many islands and coastal areas receiving more than 1,700 kWh of solar energy per square metre each year. That abundance makes a solar thermal collector far more productive here than in northern Europe, shortening the payback period to as little as three to five years on a well-chosen system.
For holiday-rental owners the economics are especially compelling: hot water demand peaks in summer exactly when solar production is highest, meaning you can run a busy rental property through the high season with virtually no energy cost for hot water. Hotels with multiple rooms benefit from the same alignment and can stack multiple collectors on a flat roof without compromising aesthetics.
Choosing the right system for your property
The two most common collector types in Greece are flat-plate collectors and evacuated-tube collectors. Flat-plate units are robust, widely serviced, and well-suited to the mild Greek climate. Evacuated-tube systems extract slightly more heat on overcast days and in cooler periods, making them a better choice for properties used year-round at higher elevations such as in the Peloponnese mountains or northern Greece.
For a typical household of three to four people, a 200-litre thermosiphon system with two square metres of collector area is sufficient. Rental properties and small hotels should size up: budget roughly 50 litres of tank capacity per occupant per day. Always pair the collector with an electric or gas backup element inside the tank so guests always have hot water on cloudy winter days.
How to install a solar water heater: 5 key steps
- 1
Plan the roof position and obtain permits
Identify a south-facing roof section with no shading between 9 am and 3 pm. In Greece, solar thermal installations on residential properties are generally exempt from planning permission under Law 4067/2012, but check with your local authority (Dimos) and, for listed buildings or archaeological zones, with the relevant ephorate. Mark the exact mounting points before ordering brackets.
- 2
Prepare and mount the roof frame
Fix stainless-steel or hot-dip-galvanised mounting rails to the roof structure using appropriate fixings for your roof type — expanding anchors for concrete flat roofs, purpose-made tile hooks for pitched roofs. Angle the collector at latitude plus 10 degrees (approximately 47–50 degrees for most of mainland Greece, 40–43 degrees for Crete) to maximise year-round output. Seal every roof penetration with EPDM flashing collars to prevent water ingress.
- 3
Lift and secure the collector and tank
For a thermosiphon system the tank sits directly above the collector on the same frame, so the two must be lifted together or assembled in place. Use a two-person team and a roof pulley for anything above 80 kg. Bolt the tank bracket to the frame first, then slide the collector into its lower brackets. Tighten all fixings to the torque values in the manufacturer's data sheet — Greek summer winds can gust above 100 km/h on exposed island sites.
- 4
Connect the plumbing and fill the circuit
Run 22 mm copper or stainless-steel pipe from the cold-water supply to the collector inlet and from the tank outlet to your hot-water distribution point. Install isolation valves on both lines, a pressure-relief valve set to 6 bar, and a non-return valve on the cold feed to prevent backflow. For a closed-loop pressurised system, fill the collector circuit with a 30 percent propylene-glycol antifreeze mix, then pressurise to 2.5 bar with a hand pump. Thermosiphon systems use potable water directly — just open the supply valve slowly and watch for leaks at every joint.
- 5
Test, insulate, and commission the system
On a sunny morning, verify that the tank temperature rises at least 5 °C per hour with the backup element off. Lag all exposed pipe runs with 19 mm closed-cell foam insulation, paying particular attention to the section between collector and tank where heat loss is greatest overnight. Check that the pressure-relief valve opens and reseats cleanly by briefly lifting the lever. Record the final tank pressure and the date; most Greek manufacturers recommend a full system check every two years, including an anode inspection inside the tank.
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FAQ
- Do I need a backup heater alongside the solar collector?
- Yes. Even in Greece, overcast spells in winter can last several days, especially in northern regions and at altitude. All quality solar water heaters sold here include an integrated electric resistance element (typically 1.5–3 kW) inside the tank. This switches on automatically via a thermostat if the solar-heated water drops below a set temperature, ensuring guests or residents always have hot water regardless of the weather.
- What maintenance does a solar water heater need in Greece?
- Annual maintenance is light. Rinse the collector glass with water in spring to remove salt deposits near the coast and dust from Saharan dust events. Every two years have a technician check the glycol concentration in pressurised systems (it degrades over time), inspect the anode rod inside the tank, and verify that the pressure-relief valve operates correctly. Hard water in many parts of Greece can cause limescale on electric elements; a descale every two to three years extends element life significantly.
- How much can I save on my electricity bill?
- A correctly sized thermosiphon system in southern Greece typically offsets 70–80 percent of annual domestic hot-water energy, translating to roughly 300–600 EUR per year in savings for a four-person household at current Greek electricity rates. Coastal holiday rentals with high summer occupancy can see payback in three to four years. The exact saving depends on your current tariff, occupancy, and system sizing, but solar water heating consistently ranks as one of the highest-return energy upgrades for Greek properties.