Heat pump versus electric heater: the simplest comparison in industrial heating

Against a resistance heater the comparison needs no fuel price, no calorific value and no boiler efficiency. Both machines run on the same electricity at the same tariff, so the whole question is how much heat each delivers per unit consumed.

A resistance heater converts one unit of electricity into approximately one unit of heat. An industrial heat pump moves two to five units of heat for each unit it consumes. It does not make that heat. It moves it from somewhere else. Our water source units reach COP 4.5 to 5.2 at 60°C output. Performance falls as the output temperature rises toward the 120°C ceiling.

Why is this comparison simpler than the others?

One whole side of the arithmetic cancels out.

Comparing a heat pump with a gas boiler means establishing a gas price, a calorific value, a boiler efficiency and an electricity tariff. Each of the four can move the answer.

Against a resistance heater there is nothing to argue about. Both use the same energy source, the same tariff and the same meter. The only variable left is how much useful heat each machine delivers per unit drawn, and that is the coefficient of performance.

So the running cost ratio is the COP. At COP 3.0 the heat pump costs a third as much to run. At COP 2.0 it costs half. There is no version of the comparison where a working heat pump loses on running cost inside its temperature range.

What COP should you expect at your own temperature?

Use the COP at your own duty. It is the only number in this comparison that needs care.

Coefficient of performance falls as the gap between source and output widens, because the compressor does more work per unit of heat delivered.

Output temperature	Expect	Running cost against resistance
60°C, water source	COP 4.5 to 5.2 at the rated point	About a fifth
110°C	About 2.26, measured in Indian conditions	Under half
120°C	About 2.0, measured in Indian conditions	About half

At the ceiling, a heat pump is working hardest. Even there, it uses about half the electricity of a resistance heater for the same delivered heat. That is the floor of this comparison.

Most industrial hot water duties sit far below the ceiling. Wash tanks, degrease baths, pasteurisation loops and CIP circuits run between 50 and 90°C, which is the comfortable end of the curve. There is more on why lift drives everything in how the cycle works.

What it does to connected load, and what that is worth

This part is often worth more than the energy saving, and most comparisons leave it out.

A resistance heater draws roughly its thermal duty. At 97% efficiency, a 500 kW thermal duty needs about 515 kW of electrical input. A heat pump serving the same duty at COP 3.5 draws about 143 kW.

That is roughly 372 kW of connected load you do not have to sanction. Its value depends on where your plant sits relative to its contract demand.

• If you have headroom, the value is the demand charge you avoid. Maharashtra HT-I demand charges run ₹650 per kVA per month. So the difference recurs every month.
• If you do not have headroom, the value is the enhancement you avoid entirely. You avoid the application, the possible service connection charge and the metering. You also avoid the security deposit recalculation that follows the bill. What that costs is set out here.

A plant close to its sanction can find that the electrical case decides the project before the energy case is even discussed. Run the headroom check for both options side by side.

What does it cost to run, in rupees?

These figures use the Maharashtra HT-I energy charge of ₹8.44 per kVAh.

Heat source	Per useful kWh thermal	Per useful million kilocalories
Electric resistance, 97% efficient	₹8.70	₹10,117
Heat pump at COP 2.5	₹3.38	₹3,926
Heat pump at COP 3.0	₹2.81	₹3,271
Heat pump at COP 3.5	₹2.41	₹2,804

Maharashtra bills HT-I per kVAh, not per kWh. So a plant with poor power factor pays more per useful unit than ₹8.44 suggests. That applies equally to both machines, so it does not change the ratio, but it does change the absolute numbers. The full cost-of-heat comparison across every fuel puts these rows in context.

Where does resistance heating still win?

There are four cases.

Above the temperature range. A heat pump stops at 120°C. Resistance heating does not, and for duties above that it remains one of the simpler electric options.

Very small duties. Below the point where an industrial machine can be justified, a resistance heater is the right answer. Single units start at 100 kW, and a 15 kW duty is not a heat pump project however good the physics looks.

Duties that run a few hours a year. Capital equipment earns its return on running hours. A heater used during an annual campaign or for occasional trace heating will never repay the difference in capital cost, whatever the COP.

Where the heat has to go somewhere a water circuit cannot. Examples are an immersion element inside a vessel, a cartridge heater in a die and trace heating on a pipe run. These are duties where the delivery method matters more than the efficiency, and there is no hot water loop to be had.

Resistance heating also wins outright on two things that have nothing to do with energy: capital cost per kilowatt, and simplicity. There is no refrigerant, no compressor, no source side, no water treatment and almost no maintenance. On a duty where those advantages outweigh a running cost two to five times higher, resistance is the correct engineering choice.

The electric boiler case

An electric boiler is resistance heating with a pressure vessel around it, so everything above applies to its running cost unchanged.

What it buys that a heat pump does not is steam. A retort, an autoclave and a sterilise-in-place cycle need saturated steam at pressure. If your duty needs steam of that kind, compare the electric boiler with a fired boiler. That is a fuel price question.

On most Indian sites a large share of the steam header is serving duties that need a temperature, not steam. On those, the heat pump wins on running cost by the margin of its COP. It also avoids the boiler registration that a pressurised electric boiler still attracts. Which duties need steam, and which never did, is worth settling before either machine is specified.

Watch for one thing in a quotation. An electric boiler is often proposed as the simple route to decarbonisation. It is a direct swap for a fired boiler and needs no source side. It is also the most expensive electric heat a plant can buy, because it gives up the multiplier a heat pump gets from moving heat.

What to do next

Work out the output temperature your duty actually needs, and the hours a year it runs. Those two decide the question.

Suppose the duty sits inside the temperature range and runs real hours. Then a heat pump costs between a fifth and a half as much to run as resistance heating. It also draws a fraction of the connected load. Outside the range, or on a duty that runs occasionally, resistance is the right answer and the comparison ends there.

The savings calculator runs the arithmetic on your own tariff. The sizing guide turns your flow and temperature rise into a kilowatt figure. The specification page sets out where the equipment stops. When you have the duty and the hours, send them to us.