COP depends strongly on source and sink temperatures (Sadjjadi et al., 2023), so make sure you have a strong understanding of your temperature requirements and dynamics before talking to vendors. The process must also keep running if the heat pump trips, which means retaining backup steam is often in the cards (DOE, 2003). DOE's thresholds provide a useful rule of thumb when considering energy cost: an electricity-to-fuel price ratio below 3 favors a heat pump, and above 6 argues against it (DOE, 2003).

You must also consider your boiler efficiency, so a COP of about 4.4 breaks even when electricity costs about 5.5 times boiler fuel per unit of energy at 80% boiler efficiency. DOE historically reports simple paybacks of 2-5 years.

Recent analysis has shown a ~500 kW unit, condensing at 145°C from a 71°C source, paid back in 3.9 years (Hamid et al., 2023). Plants, however, tend to fund heat recovery only when paybacks run well under three years, so your mileage may vary.

Plant and policy

If you are in the EU, carbon prices may enter the conversation when considering heat pumps. For example, if we take €90/t carbon, the boiler's direct emissions may be worth considering. Taking 210 grams of CO₂ per kWh as the emissions factor, running the 500 kW heat pump for 2,000 hours, 4,000 hours, or 24/7 could avoid €18,000 or €37,800 or €82,800 per year, respectively.

However, you need to consider regulatory standards when selecting your technology, specifically the fluid. The F-gas revision tightens market access for fluorinated refrigerants, and a proposed The per- and polyfluoroalkyl substances, or PFAS, restriction under the EU’s REACH regulation would cover most of them, HFOs and HCFOs included (Bever et al., 2024).

Other things to consider for your site should begin with cogeneration. When lower steam demand backs down on-site power generation, the extra power purchase may reduce your savings. Small streams that cool quickly force the heat pump to raise its lift. This also can have a negative impact on savings over time. Heat fluctuation and uncertain long-term reliability should be among key decision drivers for your investment.

Another point to consider is that a heat pump adds rotating equipment, so first run a pinch analysis to confirm that you haven’t overlooked a simpler recovery project.

Flexibility

A recent mapping of published reports on energy-flexible heat pumps found no studies of units above 100 kW that combine industrial heat supply with price-driven operation or grid services (Sadjjadi et al., 2023). Because grid-responsive technologies and facilities are nascent, today’s approach keeps the need for industrial processes to have constant temperatures and firm supply, and storage above 100°C requires pressurized water or vapor. But as electricity demand continues to rise across all sectors and more technology for flexible operations emerges, heat pumps, namely variable speed ones, can be part of the shift in operations and energy savings.