4 ms·
Modern heat pumps work down to pretty low temperature, but the amount of heat you can get out at a low temperature may not be enough to stay warm with. As outsi
by moloch-hai 4y ago
Modern heat pumps work down to pretty low temperature, but the amount of heat you can get out at a low temperature may not be enough to stay warm with. As outside temperature goes down, you need an increasing amount of heat input. At a particular point (which depends on temperature and wind speed) capacity is exceeded, and inside temperature falls. Then you need an alternative source of heat.
Typically this is a propane furnace, but may be a resistive heater. The heat pump saves on your bill except during cold snaps, and then cost spikes.
- thehappypm 4y agoTypically the backup is resistive, in a ducted system, it’s basically a big heater coil in the heat exchanger area. One of my two properties has one. It has never been used though, AFAIK, because it hasn’t gotten cold enough yet (and frankly, in Eastern Massachusetts, it is not very common anyway).
- lsllc 4y agoIf you have propane/nat gas for hot water, you can use that as the backup heat -- just need a combi-boiler with a single zone through a hydronic loop in the air handler stack.
- thehappypm 4y agoI do not, no gas line to the house. I had an oil furnace which I replaced hydronic with heat pump + resistive backup. Saving about $300/month this winter
- pxmpxm 4y agoThis - we've got a brand new Daikin heat pump at 10F/-12C outside temp, it took full 24 hours to bring our place from 50F/10C to 72F/22C. A regular nat gas furnace would knock it out in about and hour and half, and at fraction of the cost. Incidentally we're in the process of installing a nat gas tankless combi heater to address this issue - you can get a forced air set up with those.