Higher efficiency panels + vertical panels would help. Most houses have decent south-facing walls.
Ground mount is also an option in many places.
Live underground and convert your whole yard to arrays of panels!
6.7kW ground mount here in NM, still can't heat my home in winter in this climate (would need 21kW with my Mitsubishi hyper-heat units). We have relatively OK passive solar contributions too.
6.7kw is tiny. The smallest install I’ve personally seen is 15kw.
Pretty standard size for New Mexico. I have numerous neighbors with 6-12kW systems.
20kW ground mount array in NH produces twice as much as we need for our 4 heat pumps heating 3000 sqft. Went into the last two winters expecting to deplete our summer credits with the power company but we have only used about 1/6th of it.