In Luxembourg, there are two different systems, depending on the type of property you are renting.
Renting a House
For houses, the tenant is required to pay the landlord the rent upfront, and will then be billed separately for electricity, water, gas, refuse collection, television & internet, etc., by each provider. For electricity, water and gas, as a rule, the tenant will be billed a fixed amount in advance, every one, two or three months, based on average past consumption for the property. At the end of the year, real consumption will be calculated and the amount billed will be revised, up or down, for the upcoming 12 months. Depending on circumstances, the tenant will either have to pay the difference for excess consumption or receive a refund (usually as a credit against the provider) if consumption was lower than expected.
Renting an Apartment
In the case of flats, the landlord will request a certain amount in advance which is supposed to cover a series of costs. Usually these are communal costs (costs shared by the whole property such as electricity in the common areas), water and heating (e.g. gas). This is only a general rule and the owner can decide what is included in or excluded from this amount. It is always a good idea to check the lease agreement to be clear as to what is covered. The same yearly revision applies as well in this case but the owner is required to transfer any surplus back into the tenant’s account if not otherwise stated in the lease. If consumption is too high, the tenant will have to pay the difference to the owner and both can then agree on an increased monthly payment for the future.
All other providers have to be contacted separately by the tenant, and will send a bill at the end of every month for the previous month’s consumption.
EN 
FR