What's the lower proportion renewable sources produced in the last 12 months (in one minute intervals)? If that is much lower than 90% you have to have some other source (or accept frequent randomish power cuts).
Well, we're linked to the English grid, and via connectors to Northern Ireland, continental Europe, etc. In practice the difference is made up by natural gas, and the large pumped hydro storage at Cruachan.
It has been some years since I had a power cut.