I think it's even longer than that, unfortunately... of course, it depends how much over capacity you have, but those cold fronts in N Europe can kill wind speed for weeks on end sometimes IIRC. It is a huge problem for us to solve.
If everyone has an electric car then, in principle, that battery can be used to keep your house alive for quite a long time. And of course once the battery capacity has declined so that you are no longer satisfied with the car's range you can repurpose the battery for home use to store the output of solar panels on your roof.
It's a huge problem in terms of time and finance but not a difficult technological one.
I hope very few people will own electric cars in the future (or any car whatsoever). We don't need more cars on the road - we barely can squeeze them on our roads now. We need good, fast, ubiquitous public transport system.
I think it's even longer than that, unfortunately... of course, it depends how much over capacity you have, but those cold fronts in N Europe can kill wind speed for weeks on end sometimes IIRC. It is a huge problem for us to solve.