5.3.3 Straight-line depreciation has the advantage, that it can be easily based on operator accounts. However, the main disadvantage is that the return on capital changes significantly over time: As return on capital is based on the net book value of an asset, this net book value decreases over the life time of an asset to zero, leading to a very high price at the beginning of the asset life time and a zero price at the end. 5.3.4 A more adequate approach for service price setting are annuities, as they keep the combination of depreciation and return on capital constant over the life-time of an asset. The formula for calculating the annualization factor of annuities is: Cost of capital/{1-[1/(1+cost of capital)]^asset life} 5.4 Implementation of maximum service prices The results for maximum service prices for passive infrastructure sharing are shown in Annex F. This Annex also shows, how operator cost inputs have been applied to arrive at the maximum service prices. 5.4.1 Annex F section (I.) shows the maximum monthly service prices for tower sharing for the three different lattice tower categories. These prices are applicable, if an infrastructure seeker only wants to share access to a tower and can provide his own electricity supply. 5.4.2 Annex F section (II.) shows the additional maximum monthly service price for sharing electricity from the infrastructure provider. These prices include all charges for electricity and fuel usage and are in addition to the applicable tower sharing price of Annex F section (I.). Prices in Annex F section (II.) are based on the assumption, that the on-site power generator has sufficient spare capacity to cater for the needs of both, the infrastructure provider and the infrastructure seeker. 5.4.3 In the case that the existing on-site generator of the infrastructure provider does not have sufficient capacity to supply the additional power for an infrastructure seeker, both parties need to agree on one of the following two options for upgrading the on-site generator: 5.4.3.1 Option (1) for generator upgrade: The infrastructure provider arranges and pays for the generator upgrade. In this case the infrastructure provider can charge an additional monthly fee for annualized cost of the generator upgrade. Annex F section (III.) shows this additional monthly fee for this generator upgrade. 15