(8)The methodology to calculate life-cycle greenhouse gas emissions should be robust and widely applicable and thereby promote the comparability of greenhouse gas emissions calculations within and across sectors. It is therefore appropriate to demand the same calculation methodology across activities, where such calculation is required, while providing sufficient flexibility for entities applying Regulation (EU) 2020/852. Accordingly, the Commission Recommendation 2013/179/EU is useful for the calculation of life-cycle greenhouse gas emissions, with, as an alternative, the possibility to use ISO 14067 or ISO 14064-1 standards. Where alternative well-established tools or standards are particularly suitable to provide exact and comparable information on the calculation of life-cycle greenhouse gas emission for a specific sector, such as the G-res tool for the hydropower sector and the ETSI standard ES 203 199 for the information and communication sector, it is appropriate to include such tool or standards as additional alternatives for that sector.