Williams co-owner Patrick Head believes using Renault engines from 2012 will provide a better benchmark for his team and remove a degree of uncertainty about its form.
At present Williams is one of three Cosworth-powered teams, alongside the back-of-the-grid Virgin and Hispania squads.
Renault already supplies world champion team Red Bull, its own former works squad still running under the Renault name, and Team Lotus.
Head pointed out that switching from Cosworth to Renault was no guarantee of success, but would remove one question mark over Williams's package.
"A lot of these engines are very close in their ultimate performance, some of their characteristics will vary quite a bit," he said. "With Team Lotus one can see changing with engine, it didn't light their performance up.
"We are never a team that looks for excuses but if someone says how much [of the deficit] is in the car and how much in the engine, the difficulty with the current engine and with the other teams running it...
"With the Renault engine in the back of a car from Milton Keynes at the moment, if someone went around saying it is not a decent engine... The Renault engine seems to be very good across the board."
Head is also excited about the other technical opportunities offered by the Renault partnership.
"Renault got resources that are not available to us in terms of dyno facilities, and other technical areas, but it removes one of the variables of uncertainties going forward," he said. "We decided going forward, being led very much by Adam [Parr], we said 'let's go for it, this is the right direction for Williams.'"