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Solar Water Heater Calculator

Determine the exact capacity (Liters Per Day) required for your solar water heater based on your family size and bathing habits.

Family Requirements

Usage Pattern

Pricing

Standard ETC (Evacuated Tube Collector) systems cost roughly ₹15,000 for a 100 LPD system (₹150/LPD).

Thermal Expert Tips

1
LPD (Liters Per Day)

Solar water heaters are measured in LPD. This is the amount of water the system can heat to roughly 60°C in a single sunny day.

2
Standard Sizes

Manufacturers produce tanks in standard sizes: 100, 150, 200, 250, 300, and 500 LPD. You must round up your requirement to the nearest standard size.

3
Water Hardness

If your borewell water is very hard (high TDS), you must buy an FPC (Flat Plate Collector) or a heat-exchanger system, which costs slightly more than standard ETC systems.

Enter your family size to size your solar thermal tank.

The Ultimate Solar Water Heater Calculator for India (2026-2027)

Heating water accounts for a massive portion of a household's electricity or gas consumption, particularly during the winter months. Installing a solar water heater is an incredibly efficient way to slash these utility bills, paying for itself in just a few years. However, buying a system that is too small means you will run out of hot water, while buying one that is too large wastes money and roof space. Our Solar Water Heater Calculator is specifically designed for Indian households, helping you determine the exact LPD (Liters Per Day) capacity you need based on your family size, bathing habits, and regional climate conditions.

How to Calculate Solar Water Heater Capacity (Step-by-Step)

Determining your ideal solar thermal system size is quick and easy with our tool:

  • Step 1: Enter Family Size: Input the total number of people living in the house who will be using hot water daily.
  • Step 2: Select Bathing Pattern: Choose the primary bathing method. A traditional bucket bath uses much less water (approx. 25 liters) compared to a shower (40 liters) or a bathtub (75+ liters).
  • Step 3: Choose Climate Type: If you live in a region with extremely cold winters (like North India or hill stations), select "Very Cold." This accounts for the fact that you will need to mix more hot water with the freezing cold tap water to reach a comfortable bathing temperature.
  • Step 4: Review Pricing: The calculator assumes an average price per LPD for standard ETC systems. You can adjust this if you are opting for premium models.
  • Step 5: Get Your Size: Click calculate to instantly find your exact daily requirement and the recommended standard tank size (LPD) you should purchase from the market.

Engineering Formulas & Thumb Rules for Thermal Sizing

Solar water heater capacity is universally measured in Liters Per Day (LPD). The core calculation multiplies the number of users by their daily hot water consumption based on their bathing style. For example, a family of 4 using showers (40 liters each) needs 160 liters of hot water. Since solar water heaters are manufactured in standard batch sizes (typically 100, 150, 200, 250, 300 LPD), our tool automatically rounds up your exact requirement to the nearest available standard size to ensure you never run out. So for a 160-liter requirement, the system recommends a 200 LPD tank.

Current Market Rates in India & 2027 Projections

The cost of solar water heaters depends heavily on the technology used (ETC vs FPC) and the inner tank material (SS, Copper, or Glass-lined). Here are the standard rates for 2026-2027:

  • Evacuated Tube Collector (ETC) Systems: ₹13,000 - ₹18,000 for a 100 LPD system. (Most common in India, highly efficient, and cost-effective).
  • Flat Plate Collector (FPC) Systems: ₹22,000 - ₹28,000 for a 100 LPD system. (More durable, highly recommended for pressurized plumbing systems).
  • Heat Exchanger / Glass-lined Tanks: Add ₹4,000 - ₹7,000 to the base price. (Absolutely necessary if your area has hard water/high TDS to prevent scale buildup).
  • Installation & Plumbing: Usually an extra ₹2,000 - ₹5,000 depending on how far the tank is from your bathrooms.

Frequently Asked Questions (FAQ)

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

ETC (Evacuated Tube Collector) uses fragile glass tubes to trap heat, making it cheaper and very efficient in cold climates, but it cannot handle high-pressure water pumps well. FPC (Flat Plate Collector) uses a sturdy metal plate covered in glass, which is more durable, slightly more expensive, and excellent for homes using pressurized water systems.

Does a solar water heater work on cloudy days or during the monsoon?

On completely overcast or rainy days, solar water heaters will struggle to reach high temperatures. However, most modern systems come with an in-built electrical backup heater (element) inside the tank. You can switch this on manually on rainy days to heat the water, effectively turning it into a standard electric geyser when there is no sun.

What happens if my borewell water is very hard (high TDS)?

If you have hard water, standard stainless steel inner tanks will corrode quickly, and the tubes will get choked with calcium scaling. You MUST purchase a system with a "Glass-lined" or "Epoxy-coated" inner tank, and preferably use a Heat Exchanger model (where an anti-freeze/distilled liquid captures the heat and transfers it to your hard water without mixing).

Can one 200 LPD system supply water to all bathrooms in my house?

Yes, a central 200 LPD system installed on the roof can be connected to the hot water plumbing lines of multiple bathrooms. However, you should ensure that the plumbing pipes are properly insulated (using PUF or nitrile rubber) so the water doesn't lose its heat while traveling from the roof to the ground floor bathrooms.