alt Hacker NewsLast time I did the maths based on data from gridwatch the storage capacity required dropped dramatically if you over built the on the production side.
But ok, 30 million homes, 100kWh storage each, that's 3000 GWh
A 100kWh battery is about £25k, less than 1/10th the cost of the house, and less than the average new car
That doesn't seem unrealistic.
The issue is you need to design for 1-2 weeks of little to no wind and very little solar in winter, when demand is it its greatest. This is what is so tricky, unlike more southern climates where you have pretty reliable solar year round (even if its reduced, its not close to 0 which is the case in the UK). Instead of storing a day or so, you need to store weeks of energy.
Also you're forgetting residential electricity is maybe 1/3rd of total demand.