Tank size comes from people and habits, not house size. A sizing table, flat plate vs evacuated tube in UAE heat, and what to check on the roof.
Solar water heating is a natural fit for villas in Dubai, Abu Dhabi, Sharjah and Ajman. The sun is strong all year and the payback comes from electricity the water heater no longer uses. The mistake people make is sizing by the house. A solar water heater should be sized by the people who live in it and how they use hot water.
Start with daily use
A common rule of thumb is 40 to 60 litres of hot water per person per day. The lower end suits short showers; the upper end suits baths, long showers and a lot of laundry and dish washing on hot cycles.
| Household | Daily hot water | Typical tank |
|---|---|---|
| 2 people | 80 to 120 litres | About 150 litres |
| 4 people | 160 to 240 litres | 200 to 300 litres |
| 6 people | 240 to 360 litres | 300 to 400 litres |
| 8 or more, or staff quarters | Over 320 litres | A larger pumped system, or two systems |
These are starting points. We confirm the size after checking actual usage and the roof. The same figures are on our solar water heaters page.
Flat plate or evacuated tube in UAE heat
Flat-plate collectors are the common choice in the UAE. They are robust, handle high temperatures well and are easy to clean. Evacuated-tube collectors are very efficient in cold, cloudy climates, but in a UAE summer that efficiency becomes a problem: the system can overheat unless it is designed to shed the extra heat. Either type needs a plan for over-temperature.
Thermosiphon or pumped
- Thermosiphon. The tank sits on the roof above the collectors, and hot water rises into it naturally. No pump, no controller, fewer parts to fail. The roof has to carry the tank's weight when full.
- Pumped (split). The tank sits in a plant room or loft, and a small circulation pump moves water from the collectors. This suits larger households, villas where a roof tank isn't wanted, and systems that serve several bathrooms.
Summer and winter
In summer a solar system can heat water well past a safe tap temperature. A mixing (tempering) valve blends in cold water so outlets stay safe. In the cooler months, roughly December to February, days are shorter and nights cooler, and a backup electric element tops up the tank. Put the element on a timer so it heats in the evening, not in the morning before the sun has had a chance.
What to check on the roof
- Direction and tilt. Collectors face south, tilted at roughly the site's latitude: about 22 to 26 degrees across the UAE, from Abu Dhabi to Ras Al Khaimah.
- Shade. Parapets, roof water tanks, AC condensers and neighbouring buildings can shade collectors for part of the day.
- Structure and wind. The frame must be anchored for wind, and fixings must not break the roof's waterproofing.
- Distance to the bathrooms. Long pipe runs mean a long wait for hot water. Insulate the hot pipes, and put the system above the bathrooms that use the most.
Hard water
Hard water leaves scale in collectors, tanks and valves, and scale cuts heat transfer. Where the supply is hard, plan periodic descaling, or treat the water before it enters the system. See water treatment if scale is already a problem in your taps and heaters.
What to send for a quote
Send the number of people, a few photos of the roof, and details of your current water heater. We supply and install solar water heaters for homes and businesses in Dubai, Abu Dhabi, Sharjah, Ajman and across the UAE. Ask for a sizing.
