The campaign was carried out under ORE Catapult's blade leading-edge erosion programme (Bleep).
ORE's research found that repair of moderate erosion could boost annual energy production by 1.5-2%.
The research and development group said the methodology used in the programme should now be applied to other offshore wind projects.
RES, on behalf of ORE, used lidars at a Centrica offshore project to measure performance before and after repairs had been carried out.
"The results will allow owner/operators to optimise their repair and maintenance strategies, balancing cost versus benefit in order to minimise levelised cost of energy impact and maximise revenue," ORE Catapult said.
Andrew Kay, ORE Catapult's innovation manager, said: "This measurement represents a single result from a single turbine type, site and level of erosion. As such it is extremely important that further studies are performed to build a more complete picture of how the level of erosion, site, turbine and atmospheric variables influence the impact of erosion on performance.
"The methodology developed and executed as part of this campaign could also be used in the assessment of proactive turbine upgrades, such as aerodynamic or control improvements, as well as to assess the impact of leading-edge protection products on power performance."