Most of the difference is in business practices, in customer acquisition. Basically all the advertising and salespeople to push solar. Lack of uniform building codes, and highly disparate permitting processes also raise costs in the US. Utilities are also hugely inconsistent throughout the US, not varying city-to-city like permitting processes, but there are thousands of different utilities in the US each with different policies. And perhaps the biggest problem is utility policies that either eliminate or make feasible solar for homes. After a utility makes solar possible by allowing favorable interconnection policies, companies rush in attempting to take advantage of the new market. But when utility executives get enough lobbying power to make solar economically infeasible through unreasonable fees, it kills existing solar installers. So the only solar companies that survive are those with large reach across lots of geographies that also have massive marketing arms that can do big customer acquisition when there's a sudden window of favorable solar interconnection policy.

I paid €3900 for 22 panels, 7.2kw system here in the Netherlands. I did install it myself (but the whole package was delivered and the electric connections done by the supplier), and the panels and inverter are cheap Chinese brands. As I didn't situate them ideally and they lose efficiency as the heat up quite drastically I expect to generate between 4500 and 5000kwh. That should save me about €800 a year so this is a pretty solid business case.

So to me the US prices seem even more ridiculous

Very interesting -- currently in WA and quite interested too. What size house you're referring to?

In the U.S. it varies by region, but mid-quality panels are usually quoted at $2.50 to $3.00 per watt installed (before subsidies). Tesla Solar is advertising $2.00/watt nationwide but there are some questions about their responsiveness in actually getting anything installed in a timely manner. Outside of CA most people are only paying $0.10-$0.13/KWh making payback rough unless you have a large state or local subsidy on top of the federal 26% tax credit.

As an example of internationally known brand/quality, here's a complete installed 6.6kw system from IKEA for AUD$5047 (AUD$3197 after subsidy).

That includes panels, inverter, mounting system, and installation.

https://www.ikea.com/au/en/customer-service/product-support/...

At this price point, it's becoming a no-brainer.

Annual fees on those farms make no sense...

We've got a quote for €6k - €2.5k subsidy for 8KW system. We use a ton of power - which is a main factor how quickly you get your money back.