It depends of the power supply unit (PSU) of you server.
400W - 480W Server Chassis
If you use server which has a 400W - 480W (Watts) PSU, at the end of the monthly service cycle, you'd probably see a bill for overage power use that varies between €14.50 - €29. It depends of your energy consumption however. It is possible not to receive an additional bill for power or one whihc is below €14.50. Please use the information in this F.A.Q article as rough calculation only.
560W - 900W Server Chassis
If your server has a PSU of 560W you have to purchase (reserve) 1 Amp additional power. It will cost you €20/month. Please note that it might or might not be sufficient. If it is sufficient you should not expect any additional charges. Depending on your power consumption however, you migth need to pay up to €15 at the end of the month.
If you server has 720W - 740W PSU you must purchase 2 Amps of additional power at €40/month. They should be enought and you'd not expect any bills over electricity consumption.
A server with 900W PSU needs 4 Amps of reserved power. However if you colocate a machine with such PSU we would charge €40/month. You should expect a bill for overage power at the end of the service cycle.
1200W Server Chassis
For 2U server that has 1200W PSU, you have to purchase/reserve 4 Amps of additional power. They will cost you €80/month. Having reserved 5 Amps (1 Amp + 4 Ams add-on), you should be OK and would not have any additional costs for electricity. If your power usages is less than 5 Amps, we will add credit for unused power to your account. You can use the credit to reduce any of your next bills.