What is Delta T?

Delta T (ΔT) refers to the temperature difference (°C) between two points, most commonly the flow temperature (temperature leaving heat source) and return temperature (temperature returning after circulation), or the emitter surface temperature (e.g., radiator or underfloor heating) and the design room temperature (target indoor temperature, typically 20-22°C).

For heat pumps, a low ΔT between the emitter surface and room temperature maximises efficiency, reduces costs, and supports sustainability. Below, we explore ΔT in these contexts, highlighting why heat pumps are ideal for UK homes.

ΔT: Flow Temperature vs. Return Temperature

This ΔT measures the difference between the hot water supplied to the heating system (flow) and the cooler water returning after transferring heat (return). It’s key to system efficiency, performance and reliability.

Why does it matter?

A low ΔT will help ensure the heat pump runs efficiently and reliably. Operating within the optimal design parameters will reduce the workload on the compressor and help increase the longevity of the heat pump.

Emitter Surface Temperature vs. Design Room Temperature

This ΔT measures the difference between the surface temperature of heat emitters (e.g., radiators or underfloor heating) and the target room temperature and influences system design.

Why It Matters

A low ΔT boosts the coefficient of performance (COP) but requires larger emitters (e.g., more underfloor loops or bigger radiators) to deliver sufficient heat, ideal for heat pumps’ low flow temperatures. Low-ΔT systems provide consistent, gentle warmth helping to enhance home comfort.

Conclusion

ΔT is pivotal in heating system design. Heat pumps’ low ΔT ensures high efficiency, low costs, and minimal emissions, making them the ideal choice for UK homes. With government support and the potential for long-term savings, heat pumps are the smarter, greener choice. For tailored advice on your home’s setup, consult a heating specialist.