en.wikipedia.org/wiki/File:Al...
en.wikipedia.org/wiki/File:Al...
Here is a data sheet from a current heat pump which shows good efficiency levels (COP ~4) from roughly 0deg outside to 35-40deg flow temperatures. No electrical heating required.
Here is a data sheet from a current heat pump which shows good efficiency levels (COP ~4) from roughly 0deg outside to 35-40deg flow temperatures. No electrical heating required.