Off Grid Heat Pump System

[tomjcarty]

I have been told it cant be done... but Im Irish and see that as a challenge.

Has anyone got a one tonne heat pump to run off of solar and batteries backed up by generator?

 

[jpwhit]

It's no problem running a heat pump off of solar and batteries. About the only thing you have to watch out for is the startup current surge for a unit with fixed speed compressor(s). Single and two speed units that have one or two fixed speed compressor(s) with have a very high startup current. So, you have to make sure the inverter can supply that much current. If you use a unit with a variable speed compressor, then you don't have to worry about that and they are much better units anyway, so I'd recommend that approach. Pretty much any minisplit will have a variable speed compressor. In more traditional split systems, with an outside condensor unit and an inside air handler, some new models will have variable speed compressor, but many will have fixed speed compressors.

 

[BarracudaBob]

Mini-split running off a 3kw inverter all night long, wonderful 73F, sleep like a hibernating bear
It has heat also but only used that 2 times in the winter. Heat pulls less energy in my neighborhood

 

[OzSolar]

I have been told it cant be done... but Im Irish and see that as a challenge.

Has anyone got a one tonne heat pump to run off of solar and batteries backed up by generator?

20 years ago that was true but two things have happened.

-PV prices have dropped by at least 75%
-Cheap Mini splits are now commonplace. Mini splits are very efficient and have no start up surge so are very off grid friendly.

 

[Partimewages]

The real issue is how much solar and batteries you need to stay sustainable. And well how much in fuel you want to spend.
Heating and cooling are usually a large long load. Takes lots of battery.
Do a heat load calculation for your location and the results will give you the Kw to figure out the rest.

 

[OffGridForGood]

Welcome to the DIY Solar Forum @tomjcarty,
It can be done,
We recently installed a 24k BTU whole house heatpump minisplit and very happy with it. The unit draws about 8kWh overnight in 30C (86F) temps maintains the whole house at 72F/ 22C effortlessly. I am so happy with the unit I am looking at another one for my business (located next door).

With the very mild weather of lreland, say about zero to 24 C type of temps a heat pump minisplit system could easily handle both heating and cooling loads in your environment. That said, the solar potential Nov-April and the high cost of utility electricity would lead me to suggest you confirm if your PV system will be able to supply the daily power you will need, and compare the cost of heating with natural gas.