A heat pump can heat the water up to 60 ° C, But we recommend not to exceed 55 ° C.
The old systems with radiators are usually designed to operate at-65 70 ° C. Then you can use the heat pump in the off seasons and days less cold.
If instead the radiators are designed to operate at 50 ° C or even less (by increasing the number of elements or lengthening the time of heating), the heat pump will be usable without the aid of external sources and ensure savings interesting than the boiler, Quantifiable between the 20% and 40%.