If heat pumps don't work in the winter, how come Sweden has (as of 2022) 2.2 million heat pumps (209 per 1000 residents) and Finland 1.4 million (251 per 1000 r

If heat pumps don't work in the winter, how come Sweden has (as of 2022) 2.2 million heat pumps (209 per 1000 residents) and Finland 1.4 million (251 per 1000 residents)? https://publications.jrc.ec.europa.eu/repository/bitstream/JRC137131/JRC137131_026.pdf https://publications.jrc.ec.europa.eu/repository/bitstream/J... https://publications.jrc.ec.europa.eu/repository/bitstream/JRC137131/JRC137131_009.pdf https://publications.jrc.ec.europa.eu/repository/bitstream/J...