- A heating system comprising a heat pump is mostly designed so that the entire heating performance needed at the lowest (design) temperature of external air (so called monovalence make) is not covered by HP as HP would be unnecessarily big and costs demanding. The optimum solution is a so called bivalence heating system in which HP is designed in such a way to cover by itself the heating performance only up to a certain external temperature, e.g. of 0 to -5°C (so called bivalence condition temperature), and another heat source, e.g. an electric boiler, helps to it at lower temperatures. As it is short the period with low temperatures requiring higher heating performance than that of the heat pump, the another source share of consumption of total heating heat is less than ten per cent as a rule. When the system is designed in such a way, an optimum ratio between purchase and operating costs can be achieved and it is possible to save even up to 65% of payments for electric power for heating. In the bivalence solution the heat pump is designed for 50 to 75% of the needed heating performance as standard.
