Grandfathering guarantees that the level of support provided per unit does not change throughout the lifetime of a solar installations once it has been built and connected.
The Renewables Obligation will close to solar from April next year, but Scottish energy minister Fergus Ewing says that the guarantee is needed to maintain investor confidence and attract funding for projects before the closure deadline.
John Forster, chairman of STA Scotland, said: “This shows that the Scottish government is fully committed to solar providing as much as possible of its 100 percent renewables target for Scotland.
“Solar projects in Scotland now know what level of support they are going to get, and that they will get it for the full 20 years. It won’t be possible to cut support for Scottish projects down the line in, for example, year 15 of 20.”