Rooftop PV isn’t the best plan if you’re north of NYC. The grid can far more efficiently move power from Southern areas that don’t need significant heating in the winter up north. The transmission losses are vastly lower than the gains you get from longer days. And as a bonus you rarely need summer cooling while people south of you do.

However, if you’re in Main and don’t have a ground source heat pump then solar thermal works great. PV is panels are still only 22% efficient and you air source heat pumps don’t work well in ultra cold weather, worse you need batteries for the long nights. But with solar thermal you’re looking at ~90% efficiency for heat collection and ultra cheap energy storage in hot water tanks. You do get less power per m2 of collection area, but that’s offset by needing heat for a longer period.

Off grid solar can work in the surprisingly far north, just expect a significant premium.

It depends on your local climate. I assume the desert southwest in the US uses far more energy in the summer, for instance.

The UK is a further north than all of the US except Alaska. Seattle is about the same latitude as Paris, New York and Chicago the same as Madrid, and Los Angeles and Houston the same as North Africa.

Solar is never likely to be as important in the UK as it is for the US, but even so it seems it can be helpful because solar generation is at its highest during the summer when wind generation (over a quarter of UK total generation) is lowest.

Winter energy could be done on a (smaller) community basis ... if it constructs a large enough, well-insulated thermal mass, or is lucky to live by one. I grew up in a place where, each winter, a large lake was covered-over by a couple of feet of ice. (Often covered by snow.) The water beneath stayed liquid. A heat-pump under the ice could draw on that source.

Worldwide, the ground itself, a few feet down, stays at about 50F year-around ~~ regardless of outdoor temperature. Locally, summer heat-pumping could be directed underground in some places. Reverse in winter.

Pumping heat from where it's stored is a lot less expensive than transporting and burning fuels. We do need to get better at it.

"No amount is enough" might be true on a boat. I have a land-based deployment. In winter my 5 kWh array generates enough to heat my 2200-square-foot house, as long as I clear the snow. In summer it generates enough to air-condition. This is in addition to appliances, televisions, lights, etc. It's not like the sun turns off for six months.

Latitude matters so much for this, people love to make blanket statements forgetting that their situation doesn't apply universally.

People hardly realize (or straight up don't realize) that once you're in the tropics even the notions of summer and winter start to get fuzzy. Consider: if you're on the equator then you can go from "summer" to "winter" in only a few steps. Obviously, near the equator solar is a no brainer.

And of course the opposite is true, once you're inside the arctic circle solar is basically pointless because there literally is a period of no sun lasting anywhere from several days to several months. Of course not too many people live inside the arctic circle so it's not too much of an issue.

Even between these extremes though, the usability varies a lot.

I think isolated solar (off-grid) is probably not great unless you're close to the equator, but when you're on the grid every carbon atom displaced from somewhere is valid.

It depends what latitude you are whether the (societywide) heating load in winter or the AC load in summer is greatest. And that breakpoint is moving north all the time.

More and more people want air conditioning. I wouldn't be surprised if lots of people use more energy in the summer.

Even here in Montana, the heat going out in the beginning of winter for a few weeks was not really as obnoxious as some of the really hot days with no AC I've seen.