The concept
The heating load of a house generally falls as outdoor temperature rises. Outdoor reset control responds by reducing the target boiler or system water temperature when full design-temperature water is not required.
Why it can help
Lower water temperatures can reduce distribution losses and may improve the operating efficiency of compatible equipment, especially condensing boilers.
System compatibility matters
The useful reset range depends on the radiation, boiler type, controls and required water temperature. A system must still deliver enough heat under actual conditions.
It is not a universal percentage savings
Savings depend on the existing control strategy, climate, building load, equipment and distribution system. Treat outdoor reset as a system-control improvement, not a guaranteed payback number.