Thermal vs photovoltaic · India
Both sit on your roof and both say "solar", which is where the confusion starts. One heats water; the other makes electricity. Only the second qualifies for PM Surya Ghar — and they compete for the same unshaded space.
Two different products
| Solar water heater | Solar panels (PV) | |
|---|---|---|
| Produces | Hot water | Electricity |
| Reduces | Geyser load only | Consumption across the house |
| PM Surya Ghar subsidy | Not covered | Covered, up to 3 kW ceiling |
| DISCOM process | None | Application and net meter |
| Upfront cost | Much lower | Higher |
| Best when | You heat a lot of water | You want the bill down overall |
Last reviewed
A solar water heater is a thermal device with no electronics in the core of it. Sunlight warms water flowing through glass tubes or a flat collector plate, and the heated water collects in an insulated tank for bathing and kitchen use. It has no meter, no inverter and no relationship with your electricity connection at all.
Photovoltaic panels convert sunlight into electricity through an inverter, which can then run any appliance in the house — and where net metering applies, surplus is exported to the grid for credit. The full mechanism is in how rooftop solar works.
The practical difference: a water heater removes one load from your bill. Panels reduce your consumption generally, whatever you happen to be running.
Central assistance under PM Surya Ghar is for grid-connected rooftop photovoltaic systems. A solar water heater is not covered by it, and no amount of vendor framing changes that. If someone selling you a water heater refers to the national rooftop subsidy, they are either confused or trading on the confusion.
Some states and agencies have at times run their own promotional or incentive arrangements for solar water heating, entirely separate from the central scheme. Those may be worth asking about locally, in the same spirit as the state layers described in state top-up subsidies — but never assume such support exists, and never let it be quoted as though it were PM Surya Ghar. What the central scheme actually pays is set out in subsidy amounts.
This is the question that actually decides it, and it turns on your own usage rather than on the technologies.
In a household that heats water heavily — several bathrooms in use, and especially a cold winter in the northern plains where Dehradun or Lucknow style winters keep geysers running — electric water heating can be one of the largest single loads on the bill. A solar water heater then delivers a fast, visible reduction for a modest outlay.
In a household where the bill is driven by air conditioning, refrigeration, pumps and lighting, and hot water is a minor seasonal matter, a solar water heater will barely register. That is common across much of the south and the coastal belt. If your bill looks like the profiles in a ₹3,000 bill and the driver is cooling rather than heating, panels are the instrument that addresses it.
So: read your own bill and your own habits first. There is no universally better answer here.
This is the trade-off most buyers miss until an installer points at the terrace. A water heater occupies prime unshaded, well-oriented space — exactly the space panels want. On a cramped urban terrace, where area is already reduced by the tank, stair room and parapet shadow as detailed in roof area needed, that displacement is not trivial.
It can also be financially consequential. Because central assistance increases only up to a 3 kW ceiling, losing enough area to drop from 3 kW to 2 kW forfeits part of that ceiling — the arithmetic in 2 kW price. If a water heater is sitting unused on your roof, as is surprisingly common, reclaiming that space for panels is usually the better decision.
Where the roof is generous, of course, both fit comfortably and this whole tension disappears.
Evacuated tube collector systems use glass tubes, cost less, and are the common domestic choice. Flat plate collector systems use a sealed metal absorber, cost more, and are generally more robust, better suited to pressurised plumbing and more tolerant of poor water.
Water quality usually decides this in India. Hard water causes scaling that steadily degrades performance and can damage tubes, so in a hard water area — much of the Deccan and the north-west — the cheaper system can end up being the more expensive one. Ask directly about scaling, whether descaling is required periodically, and whether your supply needs treatment. Ask too about the backup element, because every honest installation has one for cloudy weeks and the monsoon.
A heat pump water heater uses electricity to move heat rather than generate it, delivering hot water on far less electricity than a conventional element geyser. Unlike solar thermal it works at night and through the monsoon without leaning on a backup element. It costs more upfront and does consume electricity — which is precisely why it pairs well with rooftop panels, since the panels then supply a much-reduced heating load.
Solar thermal remains attractive where sunshine is dependable and simplicity is valued. A heat pump suits households that want consistent hot water regardless of the weather.
Run the free home check with your bill and we will tell you whether your consumption is heating-driven or cooling-driven, and what capacity your roof supports. Related: units per kW · choosing an installer · payback.
They are different technologies solving different problems. A solar water heater is a thermal device: sunlight warms water directly in tubes or a flat collector and the hot water is stored in a tank for bathing and kitchen use. Rooftop solar panels are photovoltaic: they convert sunlight into electricity that can run any appliance in the house and, where net metering applies, export surplus to the grid. A water heater reduces one specific load, your geyser. Panels reduce your electricity bill generally.
No. The central assistance under PM Surya Ghar applies to grid-connected rooftop photovoltaic systems that generate electricity, not to solar thermal water heating. This is a frequent misunderstanding, sometimes encouraged by vendors selling both. Separately from the central scheme, some states and agencies have at times run their own promotion or incentive arrangements for solar water heaters, so it is worth asking locally, but such support should never be assumed to exist and is unrelated to the national rooftop scheme.
A domestic solar water heater is substantially cheaper, typically costing a fraction of even a small photovoltaic system, and it involves no DISCOM application, no net meter and no subsidy paperwork. That simplicity is a genuine advantage. The comparison is not really a like-for-like one, though, because the two save different amounts: the water heater removes a single load from your bill while panels offset consumption across the house. Judge each against the specific saving it produces for your household rather than against each other on price.
It depends entirely on how much you currently spend heating water electrically. In a household that runs geysers heavily, particularly through a cold north Indian winter, the geyser can be one of the largest single loads and a water heater then delivers a quick and noticeable reduction. In a household where the bill is driven by air conditioning, refrigeration, lighting and pumps, and hot water is used sparingly, a solar water heater will barely move the bill. Check your own usage pattern before deciding.
Yes, and many homes do, but they compete for the same resource: unshaded roof area. A water heater occupies prime south-facing space that panels would otherwise use, and on a constrained urban terrace that trade-off can reduce the photovoltaic capacity you can fit, which has financial consequences because central assistance rises up to a 3 kW ceiling. If area is tight, decide the priority deliberately. If an existing water heater sits unused, reclaiming that space for panels is often the better outcome.
Evacuated tube collector systems use glass tubes, are generally cheaper and are the more common domestic choice. Flat plate collector systems use a sealed metal absorber plate, cost more, and are typically more robust, better suited to pressurised plumbing and more tolerant of hard water. Water quality is the deciding factor in much of India: hard water causes scaling that degrades performance and can damage tubes, so in a hard water area the cheaper option can become the more expensive one. Ask about scaling and whether a softener or periodic descaling is needed.
A heat pump water heater uses electricity to move heat rather than generate it, so it delivers hot water using considerably less electricity than a conventional element geyser, and unlike a solar thermal system it works at night and through cloudy weather without a backup element doing all the work. It costs more upfront and consumes some electricity, which is a point in favour of pairing it with rooftop panels. Solar thermal remains attractive where sunshine is reliable and simplicity is valued; a heat pump suits households wanting consistency regardless of weather.
