Almost all Stern products have the two possibilities available: E versions to be powered by mains via a supplied 9V transformer or B versions to be powered by a supplied 9 V battery. Mains version have the obvious advantage of no batteries to be replaced. Moreover, as the battery in Stern products lasts 200,000 cycles, it is not a critical point anymore. If the specific place does not have the electricity requirements, battery versions can be the best option. In both cases there is no need for an electrician to install the products. Stern products are extremely easy to install, almost like a traditional faucet. Some Stern products have a special version with the battery placed inside the faucet body. Those versions are ideal in locations where vandalism is the main concern, such as stadium, restrooms at highways, etc