Heat pump versus solar water heater: what an industrial process load actually needs

For most factory loads, solar thermal and an industrial heat pump are not alternatives. Solar thermal collects heat while the sun is on the collector. A heat pump makes heat whenever it is switched on. So for a factory with a continuous or shift-bound process load, the heat pump is the dispatchable option. Solar is the way to make the electricity that runs it cheaper.

On a levelised basis, an industrial heat pump on grid power is roughly at parity with a coal-fired boiler. On captive renewables it is clearly ahead. That is the sequence worth planning: size the heat pump on the process, then work on the power contract.

Are these two things alternatives?

They are not. They do different jobs. Most factory comparisons of the two are comparing an intermittent supply against a dispatchable one.

Solar thermal is a collector. Its output follows the irradiance falling on it, and it buys heat with surface area. It needs storage or a backup to serve any load that does not follow the sun.

An industrial heat pump is a machine. Its output follows the switch. Its input is electricity, which can come from the grid, from a captive plant, or from a solar array on the same roof.

Electricity can serve any load on site, and hot water cannot. A rooftop photovoltaic array can run the heat pump, the compressors, the lighting and the office. A thermal collector can only serve a thermal load inside its own temperature range.

What decides which one suits my load?

The load profile decides it. Both technologies make hot water in the same broad range, so what matters is when your plant needs it.

Load characteristic	Solar thermal	Heat pump	What actually decides it
Daytime only, one shift	Suits	Suits	Whether you have the roof area to spare
Across two or three shifts	Needs storage or backup	Suits	Output has to be available when the sun is not
Continuous process load	Needs storage or backup	Suits	A shortfall at 2 am stops the line
Peaky draw with quiet periods	Needs storage or backup	Suits, with a buffer tank	Buffer volume, sized on the peak either way
Must hold a set temperature	Does not suit alone	Suits	Control, which a collector does not have
Roof or ground area available	Suits	Not required	What else that surface could be doing
Waste heat stream on site	Does not use it	Suits, and the COP rises	A warm stream is the cheapest source there is

The pattern is consistent. Where output has to be there on demand, the collector needs something behind it. That is usually the machine the plant was trying to avoid buying.

What about area?

Solar thermal buys heat with roof, and in an Indian factory the roof is usually the best site for photovoltaic generation too. The two compete for the same surface.

The useful question is what the plant gets from each square metre of roof for a given duty. Thermal collection returns heat, in a temperature range, to a load that must be nearby. Photovoltaic generation returns electricity, which runs anything on site, including the heat pump serving that same hot water duty.

Any factory short of roof should work out what else the area could carry before committing it to a single thermal load.

Is a heat pump on solar power cheaper than solar thermal?

The commercial answer here is about buying power.

On a levelised basis, an industrial heat pump running on grid power is roughly at parity with a coal-fired boiler. Running on captive renewables, it is clearly ahead. Against gas, furnace oil and diesel it wins on either. The breakeven coefficient of performance is only 1.0 to 1.2 against those fuels, and any working machine clears it.

Take it in sequence. Size the machine on the process duty first. Then work on the electricity that feeds it, because that is the lever with the most travel in it. The heat pump conversation and the power procurement conversation should be one conversation. In most plants, two different people hold them a year apart.

What does captive or open-access power actually cost me?

Start with the grid baseline you are trying to beat. A solar tariff quoted against the wrong benchmark proves nothing.

State and licensee	Category	Energy charge	Demand charge	Landed
Maharashtra, MSEDCL	HT-I	₹8.44 per kVAh	₹650 per kVA per month	Add duty and any time-of-day adjustment
Gujarat, GUVNL	HT-I	₹4.30 per unit	Not separately verified	₹7.50 to ₹8.50 all-in
Tamil Nadu, TANGEDCO	HT industrial	₹7.50 per kWh	₹608 per kVA per month	Plus 5 percent electricity tax
Karnataka, BESCOM and the other ESCOMs	HT-2(a)	₹6.70 per unit plus 35 paise surcharge	₹365 per kVA per month	About ₹7.05 before duty
Uttar Pradesh, UPPCL	LMV-6, Small and Medium Power	₹9.02 per unit average billing rate	Not verified	Already all-in

Two rows carry conditions that change the answer. The Uttar Pradesh figure is LMV-6, a small and medium power category. Do not read it as the rate a large plant would pay. Maharashtra bills HT-I per kVAh, not per kWh. So a plant running poor power factor pays more per useful unit than ₹8.44 suggests.

Then add what open access costs on top of whatever generation rate you are quoted. For FY2026-27, commercial and industrial consumers in Gujarat carry a cross-subsidy surcharge of ₹1.33 per kWh. Wheeling is ₹0.2352 per unit at a 6.5 percent loss. Those are Gujarat’s charges and they do not transfer to another state. They are also the numbers that turn a headline solar tariff into a landed one, and any comparison that skips them overstates the case.

One more figure belongs here. The Maharashtra regulator has approved a declining HT-I path, from ₹8.44 per kVAh in FY2026-27 to ₹7.45 by FY2029-30. Even the grid baseline is on a published downward track in the home state.

Can I run both?

Yes, and for a lot of plants that is the right answer.

Solar thermal preheats into a buffer tank, and the heat pump lifts from that buffer to the delivery temperature the process needs. The value is in the lift. A machine raising water from 45°C instead of from 25°C does less compression work for the same delivered temperature. Its coefficient of performance rises accordingly. There is more on how source temperature moves COP in the comparison of air source and water source configurations.

In this configuration, solar thermal works as a source feeding the machine. Any preheat source does the same job. A warm effluent stream, a cooling tower return or a condensate line lifts the COP the same way. It usually costs less than a collector array and takes no roof.

Where does this show up in Indian plants?

Both technologies get pitched at the same places. These are hotel and campus hot water, laundry, canteen and washroom loads, and factory pre-treatment and wash duties. At each, a solar EPC and a heat pump supplier will both turn up.

Hotel hot water is the clearest case of the load-profile problem. The guest peak is early morning and late evening, and the collector is producing in between. The hospitality page sets out how that duty is actually sized. For a factory wash line, the equivalent question is whether the line runs on second shift.

What should I check before choosing?

Check six things, in this order:

1. The load profile, hour by hour. The shape of the day decides it.
2. The delivery temperature the duty actually needs, measured at the point of use.
3. Available roof or ground area, and what else that surface could be used for.
4. Whether a waste heat stream already exists, because it beats both options as a source.
5. The power tariff, and whether open access or captive generation is available to you, with the surcharges included.
6. Electrical headroom, because an industrial heat pump raises sanctioned load and that can trigger an unplanned charge.

We build Tetra Heat Pump units in air source, water source and cascade configurations for industrial process heat. So you can choose the source around whatever the site already has, including a solar preheat loop.

What to do next

Work the arithmetic on your own duty and your own tariff. The savings calculator does it on your numbers, and the comparison of heat pump and boiler running costs shows the method behind it in full. When you have the load profile and the tariff in front of you, tell us what the duty is and we will say what fits.