There are two main types of solar water heaters sold in India: ETC (Evacuated Tube Collector) and FPC (Flat Plate Collector). Both work well — but they behave very differently with the hard borewell water common across Bangalore, Chennai, Hyderabad and much of South India.
How ETC works
ETC heaters use rows of double-walled glass tubes with a vacuum between the walls. Water enters the tubes directly and heats up. The vacuum is an excellent insulator, so ETCs perform well even on cool mornings.
How FPC works
FPC heaters use a flat, insulated box with copper or aluminium absorber fins and riser tubes, covered by toughened glass. Water (or a heat-transfer fluid) circulates through metal tubes, not glass.
Side-by-side comparison
| Factor | ETC | FPC |
|---|---|---|
| Upfront price | Lower | 20–40% higher |
| Hard water (TDS > 500 ppm) | Tubes scale quickly, efficiency drops | Better tolerance; can be descaled |
| Pressurised systems | Not suitable | Available |
| Breakage risk | Glass tubes can crack | Rugged metal construction |
| Lifespan | 10–15 years | 15–20+ years |
| Ideal for | Soft water, budget installs | Borewell water, apartments, long-term value |
Why hard water matters
Calcium and magnesium in hard water deposit inside the hot section of the system. In ETC heaters, these deposits collect at the bottom of glass tubes, blocking flow and sometimes cracking tubes. Many Bangalore borewells have hardness well above the BIS acceptable limit of 200 mg/L — which is why we usually recommend FPC, or pairing any solar heater with a water softener.
Send us your water source and we'll recommend ETC or FPC — free.
Get Free QuoteOur recommendation
- Cauvery / soft water, budget priority: Kamal ETC.
- Borewell / tanker / hard water: Kamal FPC.
- Multi-floor homes with pressure pumps: Pressurised FPC.
- Hotels, hostels, hospitals: FPC commercial system with heat pump backup.
Frequently Asked Questions
Can ETC tubes be replaced?
Yes, individual broken tubes can be replaced, but repeated scaling problems usually mean FPC was the better choice.
Does a softener help solar heaters?
Yes — softened water prevents scaling in both ETC and FPC systems and extends their life.
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Get Free QuoteDisclaimer: prices, tariffs and subsidy figures are indicative and based on publicly available information at the time of writing; they can change. Contact us for current, site-specific figures.
