A. When used in this article, unless expressly stated otherwise: “Apartment house” means a building or buildings with the primary purpose of residential occupancy containing more than two dwelling units all of which are rented primarily for nontransient use, with rental paid at intervals of one week or longer. Apartment house includes residential condominiums and cooperatives, whether rented or owner occupied. “Campground” means the same as the term is defined in § 35.1-1. “Campsite” means that same as that term is defined in § 35.1-1. “Dwelling unit” means a room or rooms suitable for occupancy as a residence containing kitchen and bathroom facilities. “Energy allocation equipment” means any device, other than submetering equipment, used to determine approximate electric or natural gas usage for any dwelling unit or nonresidential rental unit within an apartment house, office building or shopping center, or campsite at a campground. “Nonresidential rental unit” means a room or rooms in which retail or commercial services, clerical work or professional duties are carried out. “Office building” means a building or buildings containing more than two rental units which are rented primarily for retail, commercial or professional use, with rental paid at intervals of one month or longer. “Owner-paid areas” means those areas for which the owner bears financial responsibility for energy costs which include but are not limited to areas outside individual residential or nonresidential units or campsites or in owner-occupied or owner-shared areas such as maintenance shops, vacant units, meeting units, meeting rooms, offices, swimming pools, laundry rooms, or model apartments. “Shopping center” means a building or buildings containing more than two stores which are rented primarily for commercial, retail or professional use. “Submetering equipment” means equipment used to measure actual electricity or natural gas usage in any dwelling unit or nonresidential rental unit or campsite when such equipment is not owned or controlled by the electric or natural gas utility serving the apartment house, office building, shopping center, or campground in which the dwelling unit or nonresidential rental unit or campsite is located.