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.