The company was granted planning permission for the Heckington Fen windfarm in Lincolnshire 12 months ago.
The deadline for the RO closes on 31 March 2017, although the Department of Energy and Climate Change (Decc) introduced a 12 month grace period for projects still finalising grid connections or radar upgrades.
This extension has allowed Ecotricity to opt for the RO system.
Vince Dale, founder of Ecotricity, said: “CfD comes with new risks and uncertainties which are difficult to quantify.
“It’s not just because it’s new, it’s a very different approach and it introduces a lot of new risk for projects.
“While we will have to deal with CfDs eventually- as the only game in town – for now we have the choice and the RO is a far simpler and less risky process.”