Is a solar water heater mandatory for new buildings?
There are two separate rules, and people often confuse them.
- The state rule enforced through ESCOMs (since 2007). Karnataka made solar water heaters compulsory for new houses of 600 sq ft or more built on sites of 1,200 sq ft or more. BESCOM enforced it strictly from April 2009, giving only a temporary connection (at a much higher tariff) to houses without one. When KERC withdrew the solar rebate in 2023, the reason given was that solar installation was already mandatory for buildings of 600 sq ft and above.
- The Bengaluru building bye-law. BBMP Building Bye-laws 2003, Bye-law 29 and Table 17, require solar water heating of 100 litres per day for a single dwelling of 200 sq m floor area or a site of more than 400 sq m, and 500 litres per day for every 5 flats in apartments. It also sets norms for hotels, hostels, hospitals, kalyana mantapas and industrial canteens.
How strictly the connection-stage check is applied today varies by ESCOM and subdivision, and other cities follow their own bye-laws. Ask your subdivision when you apply for the new connection, and ask your architect what the sanctioned plan says. Fitting the heater after the inspection has been refused costs more than planning it in.
What happened to the 50 paise rebate
For years, domestic consumers with a solar water heater got a rebate of 50 paise per unit, up to ₹50 a month, on the electricity bill. KERC discontinued it in its 2023 tariff order (reported in June 2023), not only for homes but for commercial, industrial, irrigation and other categories too. The current 2025 tariff schedules have no solar water heater rebate.
Some ESCOM web pages and installer brochures still mention the old rebate. If a salesman uses it to justify a price, he is out of date. The saving now comes only from the geyser units you no longer use.
We also found no current central (MNRE) capital subsidy for domestic solar water heaters. Some installer sites quote old subsidy figures; ask for a written government order before you believe them.
What size do you need?
Heaters are sold by litres per day (LPD) at about 60 °C. Because you mix it with cold water, hot water at that temperature goes a long way.
| Household | Suggested size | Notes |
|---|---|---|
| 2–3 people, one bathroom | 100 LPD | The usual minimum for a family |
| 4–5 people | 150–200 LPD | The most common size in Karnataka homes |
| 6–8 people, or two bathrooms used in the morning | 250–300 LPD | Consider two smaller units on separate lines |
| Apartments (Bengaluru bye-law) | 500 LPD per 5 flats | Central system or individual units, as per the plan |
As a rule of thumb, plan 35–50 litres per person. Families that use hot water for washing clothes or utensils, or for elderly members' baths in the evening, should go a size up. A south-facing, shade-free spot is essential; in Bengaluru, Mysuru or Belagavi winters the water is noticeably cooler on cloudy days.
ETC or FPC: which type?
| ETC (evacuated glass tubes) | FPC (flat plate collector) | |
|---|---|---|
| Price | Lower | Higher |
| Cloudy / cold days | Better heat retention | Slightly lower output |
| Hard borewell water | Tubes scale up and need regular cleaning | Copper risers also scale; models with a heat exchanger cope better |
| Breakage | Glass tubes can crack (hail, stones, monkeys); replaceable one by one | Sturdier toughened glass sheet |
| Pressure systems | Usually non-pressurised | Better for pressurised and high-rise use |
| BIS standard | Tanks: IS 16542 | Collectors: IS 12933 |
Since 12 April 2025, solar water heaters and their key components sold in India must carry the BIS standard mark under the Solar Thermal Systems (Quality Control) Order. Check for the ISI mark and licence number on the collector and tank.
Field advice: much of Karnataka draws hard borewell water. Whatever type you choose, ask for a scale-resistant tank lining, plan a drain valve for descaling, and if your water is very hard (white deposits on taps within weeks), consider a softener or an FPC with a heat exchanger.
Cost and savings against an electric geyser
Prices below are market ranges quoted by Bengaluru dealers in 2025, including standard installation; plumbing changes and pressure pumps are extra.
| Size | ETC | FPC |
|---|---|---|
| 100 LPD | ₹18,000–₹22,000 | ₹22,000–₹27,000 |
| 200 LPD | ₹25,000–₹30,000 | ₹30,000–₹36,000 |
| 300 LPD | ₹35,000–₹42,000 | ₹40,000–₹48,000 |
The saving. A 2 kW geyser running one hour a day uses about 2 units a day, 60 units a month. At ₹5.80 a unit plus charges that is roughly ₹400 a month. Renewable energy agencies quote savings of up to about 1,500 units a year for a 100 LPD heater replacing a geyser; that figure assumes heavy use, and Karnataka's milder climate usually means less. A realistic family saving is in the range of 500–1,200 units a year, depending on how much the geyser was used.
A geyser is often what pushes a family over its free Gruha Jyothi units, or over 200 units, in the cooler months. A solar water heater takes most of that load off the meter and can keep the bill at zero. For many homes, that makes it a better first buy than rooftop solar panels. Compare with our rooftop solar cost guide.
Solar water heater, heat pump or rooftop panels: how to choose
A solar water heater is not the only way to cut geyser units. Which one suits you depends on your roof, your hot water use and whether your bill is already zero.
| Option | Best for | Watch out for |
|---|---|---|
| Solar water heater | Independent houses with a sunny terrace and morning baths; families whose geyser pushes them over their free units | Long pipe runs to lower floors, hard water scaling, weak output on cloudy monsoon days |
| Heat pump water heater | Flats with no terrace access, homes with heavy hot water use through the day | Higher purchase price, needs space with airflow, still uses electricity (roughly a third of a geyser's units) |
| Rooftop solar panels plus the existing geyser | Homes that pay a full bill for many loads, not just hot water | Higher cost; saves nothing if your bill is already zero under Gruha Jyothi |
| Timer on the existing geyser | Small families, light use | Cheapest step, but only cuts the units wasted by leaving it on |
A simple test: look at your bills for December and January against April and May. If winter bills are clearly higher and you have no ACs, the geyser is the main load and a solar water heater is the right first buy. If summer bills are higher because of ACs, rooftop solar under PM Surya Ghar addresses more of the bill. Our appliance units guide helps you split the bill by appliance.
Flats in an apartment usually cannot put individual heaters on the common terrace without the association's approval. A society-wide system, or a heat pump on the utility balcony, is often the practical answer; see solar for apartments for how terrace space is shared.
Keeping it working through the year
Most solar water heaters that "stop working" in Karnataka homes have not failed. They have scaled up, lost their cold-water feed, or been shaded by a new building next door. A simple routine keeps them going for many years:
- Descale every year if you use borewell water, more often if the water is very hard. Ask the installer to show you the drain valve and how to flush the tank.
- Clean the glass (tubes or plate) every few weeks in the dry season. Dust from construction sites and roads cuts output noticeably.
- Check the cold water tank level. If the overhead tank runs dry, the heater can overheat or empty itself. Keep the solar heater's feed below the tank's outlet for other uses, so it never runs dry first.
- Monsoon months. On the coast and in Malnad districts (Shivamogga, Chikkamagaluru, Kodagu, Hassan) weeks of cloud mean the electrical backup does most of the work from June to September. That is normal. Set the backup thermostat sensibly and switch it on only when needed.
- Monkeys and stones. In many towns, ETC tubes are broken by monkeys or children's cricket balls. A mesh guard is cheap compared with replacing tubes.
- Hot water pipes. Use pipes rated for hot water and insulate the run. Ordinary PVC lines soften and leak.
If you are building a new house, ask the plumber to bring a dedicated hot-water line from the terrace to each bathroom while the walls are open. Retrofitting later means chasing walls or running ugly external pipes. Our house construction electrical guide covers the backup heater's wiring point and earthing.
Installation checklist
The backup heating element is an electrical appliance on a wet roof. It needs a proper earth and an RCCB on the circuit like any geyser. See our monsoon electrical safety guide.
Solar rules in Karnataka changed in August 2026 and tariffs are revised every control period. This article explains how things work in practice. Before you sign or pay, confirm the current rule on pmsuryaghar.gov.in, your ESCOM's DSPV / SRTPV portal, the KERC website, or your subdivision office. The ESCOM helpline is 1912.
Questions
Is a solar water heater mandatory in Karnataka?
Karnataka has required solar water heaters since 2007 for new houses of 600 sq ft or more on sites of 1,200 sq ft or more, enforced through ESCOMs at the connection stage. Bengaluru's 2003 building bye-laws also set solar water heating norms by building type. How strictly it is checked varies, so ask your ESCOM subdivision and architect.
Is there still a rebate on the electricity bill for solar water heaters in Karnataka?
No. The rebate of 50 paise per unit, up to ₹50 a month, was discontinued by KERC in its 2023 tariff order.
What size solar water heater does a family of four need?
Usually 150–200 litres per day. Plan about 35–50 litres per person, and go bigger if hot water is used for laundry or two bathrooms are used together in the morning.
Which is better, ETC or FPC?
ETC is cheaper and retains heat well on cloudy days, but glass tubes can break and scale up with hard water. FPC costs more, is sturdier and suits pressurised systems. For very hard borewell water, an FPC with a heat exchanger or a water softener is advisable.
How much does a 200 litre solar water heater cost in Bengaluru?
Dealer prices quoted in 2025 were about ₹25,000–₹30,000 for ETC and ₹30,000–₹36,000 for FPC, plus any extra plumbing.
Is BIS certification required for solar water heaters?
Yes. Since 12 April 2025, solar water heaters and key components sold in India must carry the BIS standard mark under the Solar Thermal Systems Quality Control Order.
Is a heat pump better than a solar water heater?
A heat pump suits flats without terrace access and homes using hot water through the day, but it costs more and still uses electricity, roughly a third of a geyser's units. A solar water heater on a sunny terrace uses almost none outside cloudy spells.
Sources
Rules and figures in this article were checked against these sources on 30 Sep 2026. Schemes and tariffs change, so confirm with the official office before you act.
- Solarthermalworld: Successful solar energy bylaw in Bengaluru
- Solarthermalworld: India, mandatory use of solar water heaters not welcome (2012)
- Bangalore (BBMP) Building Bye-laws 2003, Bye-law 29 and Table 17
- Public TV: Power consumers lose rebate for solar installations after KERC order (Jun 2023)
- KERC Tariff Order 2025 schedules, HRECS copy (no SWH rebate)
- MNRE: Solar water heaters (standards, BIS-approved manufacturers)
- The Live Nagpur: BIS certification mandatory for solar water heaters from April 2025
- HAREDA: Solar water heating system (savings, temperature)
- Vandana Agencies: Cost of solar water heater in Bangalore (Apr 2025)
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We handle the electrical work and the ESCOM, KPTCL and CEIG liaisoning anywhere in Karnataka, with BESCOM, MESCOM, CESC, HESCOM and GESCOM. Email basavalalith.electricals@gmail.com or use the enquiry form.
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