If you're renting out rooms in a building for commercial activities, the electricity company may require you to convert your domestic meter to a commercial one and could impose fines. The classification depends on the tenants' activities, not just the fact that the property is rented. It's advisable to approach the electricity company to convert the connection to commercial, potentially with separate meters for each tenant, to comply with regulations and avoid further penalties. Failure to comply could also lead to action from the local municipality.