For an SME with 50 to 250 employees, allow 9 to 12 months for a 100% in-house assessment, compared with 4 to 6 months with a consultancy. The difference mainly comes from collection across departments taking longer and developing knowledge of the method, including initial training. A mid-cap with 400 employees whose assessment Celsius audited had taken 9 months to produce it entirely in-house. Only a micro-business with fewer than 10 employees taking an educational approach can make do with a simplified assessment using ADEME spreadsheets, completed in 3 to 5 person-days.
Read the source article: Doing your own Bilan Carbone®: tools, time, limits