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Oxford study proves heat pumps triumph over fossil fuels in the cold
(www.nationalobserver.com)
This is a most excellent place for technology news and articles.
Mine has Toshiba guts. I don't know what I paid for it - now it appears to be selling for $1100. Mine defrosts but its defrost cycle just turns on AC for a bit instead of heat. Edit: Mitsubishi guts.
I reckon that’s your main issue.
You’d need a model designed for a colder climate.
Maybe for your next one!