200+ Verified Solar Water Heater & Pump Suppliers — ETC, FPC Water Heaters & DC/AC Solar Pumps for Residential, Industrial & Agricultural Applications Across India

What is the difference between ETC and FPC solar water heaters?

ETC (Evacuated Tube Collector) solar water heaters use evacuated glass tubes containing copper heat pipes — the vacuum eliminates convection heat loss, making them highly efficient even in cold or mildly cloudy conditions. They are the dominant technology in North India and at altitudes. FPC (Flat Plate Collector) solar water heaters use a flat copper absorber plate in an insulated glass-covered box — simpler construction, slightly lower efficiency in cold conditions but equivalent in warm climates. FPC is typically 10-15% less expensive for the same capacity. South India (below the Tropic of Cancer) can comfortably use FPC; North India benefits from ETC's superior winter performance.

What capacity solar water heater is needed per person?

The standard rule of thumb for residential solar water heater sizing is 25-50 LPD (litres per day) per person: 25 LPD per person for warm climates (Tamil Nadu, Karnataka, coastal areas); 35-50 LPD per person for cold climates (North India, hill areas). For a family of 4 in Delhi: 4 x 40 = 160 LPD — a 150-200 LPD system is appropriate. For hotels: allow 60-100 LPD per room (including kitchen and laundry). For hospitals: 80-120 LPD per bed. These are averages — actual sizing should be based on measured hot water consumption data where available.

What is Total Dynamic Head (TDH) and how do I calculate it for solar pump selection?

Total Dynamic Head (TDH) is the total resistance the pump must overcome to deliver water from source to discharge point. TDH = Static Head (vertical distance from water level to discharge point, in metres) + Friction Head (resistance from pipe length, bends, and fittings, typically 10-20% of static head for properly sized pipes) + Velocity Head (usually negligible for slow-speed agricultural pumps). Example: borewell with water level at 40m depth, overhead tank at 10m above ground level: Static Head = 50m; Friction Head = 7m; TDH = 57m. Select a solar pump with its duty point (required flow rate) on the Q-H curve above 57m head.

What is the PM-KUSUM scheme and how much subsidy is available for solar pumps?

PM-KUSUM (Pradhan Mantri Kisan Urja Suraksha evam Utthaan Mahabhiyan) Component B provides standalone solar pumps to farmers to replace diesel pumps. The subsidy structure: 30% Central Government subsidy + 30% State Government subsidy (most states participate) = 60% total subsidy, leaving farmer contribution of 40%. Several states (Rajasthan, Gujarat, MP) provide additional state subsidy bringing total subsidy to 70-90%, with farmer contribution as low as 10%. Applications are made through the state DISCOM or state Nodal Agency. MNRE-approved pump models from MNRE-empanelled suppliers are mandatory for subsidy eligibility.

Can solar water heaters work on overcast or cloudy days?

Yes — both ETC and FPC solar water heaters generate useful heat on overcast days, though at reduced output. On a mildly overcast day (50% irradiation), a quality ETC system will produce water at 35-45 degrees C — adequate for bathing, warm water for cooking, and hand-washing, though not the 60-70 degrees C achievable on clear days. On heavily overcast or rainy days (monsoon), output is typically 25-35 degrees C — a backup electric heating element (4-6 kWh) is recommended for applications requiring guaranteed minimum temperature on all days. Quality ETC systems consistently outperform FPC on overcast days due to the vacuum tube's low heat-loss coefficient.