Multiple standards have been established for charging technology to enable interoperability across vendors. Standards are available for nomenclature, power and connectors. Notably, Tesla has developed proprietary technology in these areas. Longer drives require a network of public charging stations. In addition, they are essential for vehicles that lack access to a home charging station, as is common in multi-family housing. Costs vary greatly by country, power supplier and power source. Some services charge by the minute, while others charge by the amount of energy received.