Frequently Asked Questions

What is the difference between a Monovalent system and a Bivalent system?

Monovalent and Bivalent are two terms you may come across with air source heat pumps.

A Monovalent system is one where the heat pump is able to cover the whole heating load of the property throughout the year without the support of any other heat source, such as a boiler.

A Bivalent system is one where the heat pump is combined with an additional or existing heat source, such as a boiler. This would be the case where during colder spells of weather where the property's heat loss would be greater, the heat pump would not be able to match the whole heating load of the property due to its lower flow temperature - this could be the case with a lot of older properties - and therefore require the additional input of the boiler to increase the flow temperature to match the heating load of that property.