Put in brand new heat pump last march. Did not have to turn on heat till mid dec. Its been a warm winter with average temp between 35 and 37 degrees but 2cnd month in a row me electric bill is over $400. I did not pay that even with the old heat pump and much lower temp outside. I thought heat pumps were cheep to run above freezing. A friend of mine has a 20yo heat pump 2x the sq footage and a hot tub on his roof and paid $136.00 last month. What should I check first 3ton carrier with puron R-410.a matching air handler, thermostat, back up heat.

What city are you in? That does not sound right.