How we supply it: Solar water heaters are arranged through a partner supplier who surveys, quotes, installs and bills them and pays us a referral commission. Tell us your family size and water source; the supplier checks the terrace and the overhead-tank height before recommending ETC or FPC.
In one line: A solar water heater is a rooftop system in which solar collectors heat water that is stored in an insulated tank and fed by gravity to the bathroom and kitchen taps.
ETC or FPC?
| Point | ETC (evacuated tube) | FPC (flat plate) |
|---|---|---|
| Hard borewell water | Copes better; tubes can be cleaned | Needs a heat exchanger (closed loop) |
| Breakage | Glass tubes can break | Sturdy |
| Cloudy-day output | Holds heat well | Drops more |
| Upfront cost | Lower | Higher |
| Pressurised systems | With heat-pipe tubes | Suited |
How a solar water heater works
A solar water heater is a rooftop system in which solar collectors heat water that is stored in an insulated tank and fed by gravity to the bathroom and kitchen taps.
ETC stands for evacuated tube collector: water heats inside double-walled glass tubes with a vacuum between the walls. FPC stands for flat plate collector: a dark metal absorber with copper tubes under glass.
System types
| Type | How it works | Suits |
|---|---|---|
| ETC, direct | Water flows into the glass tubes | Most homes, hard water |
| ETC with heat pipes | Sealed pipes carry heat to the tank | Pressurised systems |
| FPC, open loop | Water runs through copper risers | Soft water only |
| FPC with heat exchanger | A closed loop heats the stored water | Hard water, long life |
Litres per day for your family
Typical estimate: at 25–35 litres of hot water per person per day; long baths and washing machines on hot water need more.
- Family of 2–3: 100 LPD (litres per day)
- Family of 4–5: 150 LPD
- Family of 6–8: 200–250 LPD
- A 100 LPD system needs roughly 2 × 2 m of shade-free terrace; check the model's footprint
Installation essentials
- Collectors face south, tilted at roughly the site's latitude, about 13° around Chennai
- The overhead cold-water tank must sit higher than the heater's inlet so it fills by gravity
- Run the hot line in insulated CPVC, as short as possible to the bathrooms
- Fit an electric backup element for cloudy north-east monsoon weeks
- Have the terrace slab checked for the filled system's weight
Checks on the system
- The tank's inner shell material and insulation thickness should be stated in the quote.
- Collector type, area or tube count and tube length should match the quote.
- Ask for the maker's test certificate for the collector.
- A vent pipe or pressure and temperature relief valve must be fitted.
- Fill the system and check every joint for leaks before insulation is wrapped.
Upkeep
- Wipe dust and salt film off the tubes or glass every few weeks.
- Descale on the maker's schedule if your water is hard.
- Drain sediment from the tank bottom from time to time.
- Inspect tubes after storms and replace any broken ones promptly.
Solar heater mistakes
- A plain open-loop FPC on hard borewell water.
- An overhead cold tank set lower than the heater.
- Long, uninsulated hot pipes to far bathrooms.
- uPVC used on the hot line.
- No backup heating for cloudy monsoon weeks.