Definition: Weather compensation is a heating control that automatically adjusts your boiler’s or heat pump’s flow temperature based on the temperature outside, so the system generates just enough heat — running cooler and cheaper in mild weather and hotter only when it is genuinely cold.

How the curve works

An outdoor sensor (or an internet weather feed) drives a “compensation curve” — a line mapping outdoor temperature to flow temperature. A typical heat pump curve might call for 50°C flow at −3°C outside but only 35°C at 12°C outside. If rooms overheat in mild weather, the curve is set too steep; if the house lags behind on cold mornings, it is too shallow. Our guide to the weather compensation curve shows how installers tune it — and how to ask for it to be adjusted.

Not just for heat pumps

Weather compensation is standard on heat pumps, where a lower flow temperature directly raises the SCOP. Many modern condensing boilers also support it via an outdoor sensor or a compatible smart thermostat, keeping return temperatures in the condensing range for more of the year — the same principle behind Nesta’s finding that lower flow temperatures could cut gas use by around 9%.

A cheaper cousin, load compensation, adjusts the flow temperature based on room temperature rather than outdoor temperature — many smart thermostats already do this. Weather compensation generally edges it for heat pumps, and the two approaches are sometimes combined.

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