Today i went a 4hour training with my Polar cs200 just to compare the my HR and the calorie expenditure. The results was HR was +-1 pretty much the same and the calories at my polar were 2374kcal despite my 2122kj at my SRM. I know that maybe just maybe the polar isn't accurate but the difference isn't to much.
Any more infos about this would be helpfull to clear if the polar is accurate.