Netherlands is mostly rooftop solar, which is easy and cheap to install there. No permitting required, previous net metering policies gave a very predictable ROI and cost is very reasonable: say 3k eur for 8 panels including installation, that would get you like 3000kwh/year. Panels would be just over 2k, the crew to get it done like 600-800 euros. Electricity ain't electricity cheap there to the point the ROI would be just a couple years with the net metering. You'd be stupid not to get it at that point and a few thousand bucks is a very feasible investment for most people without having to resort to financing.

I live in Texas now where there's a lot more sun and a lot more electricity usage (though it's cheaper per kwh). Panels and inverters are a significant percentage more expensive due to tariffs and stuff, but that's not even the biggest cost driver. It's the permitting and installation costs that make it so so so much more expensive. If I could get a bunch of panels on my roof for $5k, they'd be there already. But typical costs I'm seeing is low five figures which is well beyond my appetite or electricity costs.

A big part of it is that The Netherlands has quite generous subsidies for roof solar panels on your home: you may subtract total power delivered to the grid from total power consumed when calculating your yearly electricity bill. This effectively means you can use excess solar generated during summer months to reduce your winter electricity bill, nullifying one of the biggest downsides of PV (intermittent generation).

The subsidy is set to expire next year, however. Although it was extremely successful in getting People to install roof solar, it is a severe adverse incentive for home battery systems (why store your generated power in a battery when you can give it to the grid and get it 100% back for free whenever), and it is making electricity more expensive for those who cannot install solar.

Looking at yearly solar irradiation actually underplays the disadvantage we have in northern Europe in terms of PV. If all we had to do is built twice the capacity that would be one thing but our winters are quite dark, making PV energy generation almost negible around the winter solstice. Whatever generation capacity we can displace in the summer we still have to keep around to make up the shortfall in December. I love when I see solar panels here but rationally speaking Germany and the Netherlands should be among the late adopters.

That’s why they need above average per capita instal.

Yes, this is honestly a huge problem. The US isn't even trying.