Why temperature lift sets the cost of heat-pump heat
An industrial heat pump's cost of heat is its electricity price divided by its COP, and the COP is set almost entirely by the gap between the source and the delivery temperature. What that means for which duties to electrify first.
A boiler turns fuel into heat and is limited to a little under one unit of heat per unit of fuel: a good gas boiler delivers about 85% of the fuel's energy to the process, and the thermodynamic ceiling is around 95%. A heat pump is the same refrigeration cycle as the chillers already on most industrial sites, run the other way round. It takes heat that already exists at a low temperature — ambient air, a chiller's condenser, warm effluent, a cooling loop — and uses electricity to push it up to the temperature the process needs.
Because the electricity only does the pushing, one kWh of electricity typically moves three to four kWh of heat. That multiplier is the coefficient of performance, COP: useful heat delivered divided by electricity consumed. Everything about the economics of electrified heat follows from it.
Lift is the whole story
How far the heat has to be pushed is the lift: delivery temperature minus source temperature. The bigger the lift, the more work each kWh of heat needs, and the lower the COP. The published anchor points jouleWise plans against are a COP of about 3.4 delivering 80 °C from a 30 °C source, falling to about 2.3 at 135 °C. The deck's lift table says the same thing from the other direction: about 5 at a 30 K lift, 3.5 at 50 K, 2.5 at 70 K.
This is why the source matters as much as the delivery temperature. Raising the source from ambient air at 30 °C to a recovered 45 °C stream narrows the lift by 15 K and can take a COP from the threes into the fours. Chiller condensers, compressor jackets and effluent are heat sources before they are waste, and recovering them is usually worth more than any choice of machine.
From COP to rupees per kWh of heat
The cost of a kWh of useful heat from a heat pump is simply the electricity price divided by the COP. At ₹5.50 per kWh of green open access electricity and a COP of 3.3, heat costs about ₹1.67 per kWh. The same duty on a piped natural gas boiler at ₹55 per SCM, 10.4 kWh per SCM and 85% efficiency costs about ₹6.22 per kWh of useful heat. On diesel it is nearer ₹10.59.
Put the heat pump on DISCOM electricity at ₹8.50 instead and the heat costs about ₹2.58 per kWh at the same COP: still well below gas, but the carbon story changes completely, as the next section explains. Put it in solar blocks with a thermal store at ₹4.00 and the heat falls to about ₹1.21.
Cheaper heat is not automatically cleaner heat
On India's grid emission factor of about 0.716 kg CO₂ per kWh, a heat pump at COP 3 emits roughly 0.24 kg per kWh of heat — about the same as the 0.22 kg from a gas boiler. It cuts the bill sharply and the carbon hardly at all. The same machine on contracted green electricity, with the instruments retired, delivers heat that is close to zero-carbon on a market basis.
That is why the order of work matters. Low-cost green electricity first, so that every unit of heat the heat pump makes is both cheaper and cleaner. Then heat, on the duties the lift allows.
The 120 °C ceiling, and what stays on fuel
The physics keeps working above 120 °C, but the machines, refrigerants and service networks get much harder, and the COP keeps falling. jouleWise treats 120 °C as the practical ceiling: hot water and low-pressure steam below it move to heat pumps; sterilisation, stenters, reactors and anything hotter stay on fuel, or move to solar thermal or electrode heat. A playbook that names those duties is more useful than one that quietly includes them in a saving.
In short/ Why temperature lift sets the cost of heat-pump heat
An industrial heat pump's cost of heat is its electricity price divided by its COP, and the COP is set almost entirely by the gap between the source and the delivery temperature. What that means for which duties to electrify first.
A boiler turns fuel into heat and is limited to a little under one unit of heat per unit of fuel: a good gas boiler delivers about 85% of the fuel's energy to the process, and the thermodynamic ceiling is around 95%. A heat pump is the same refrigeration cycle as the chillers already on most industrial sites, run the other way round. It takes heat that already exists at a low temperature — ambient air, a chiller's condenser, warm effluent, a cooling loop — and uses electricity to push it up to the temperature the process needs. Because the electricity only does the pushing, one kWh of electricity typically moves three to four kWh of heat. That multiplier is the coefficient of performance, COP: useful heat delivered divided by electricity consumed. Everything about the economics of electrified heat follows from it.
Questions this page answers
What COP can an industrial heat pump achieve?
From a 30 °C source, about 3.4 delivering 80 °C and about 2.3 at 135 °C. A warmer source raises it: about 5 at a 30 K lift, 3.5 at 50 K, 2.5 at 70 K.
How do I calculate the cost of heat-pump heat?
Electricity price divided by COP. At ₹5.50 per kWh and COP 3.3, about ₹1.67 per kWh of useful heat, against about ₹6.22 from a gas boiler at ₹55 per SCM and 85% efficiency.
Does a heat pump reduce carbon?
Only if the electricity is clean. On the grid emission factor it roughly matches gas; on contracted green electricity its heat is close to zero-carbon.