Whether on curved or straight stairs, indoors or outdoors, stairlifts are battery operated. The batteries must also be charged through a standard outlet. The batteries are charged by a regular 110-Volt outlet, near the top or bottom of the stairs. In the case of an outdoor stairlift, you will still need access to an indoor outlet, nearby. The appropriate outlet is usually chosen during a free stair survey, so you don’t have to worry about that until someone comes to see your stairs. If you’re concerned about your electric bill, don’t be. The stairlift uses about as much electricity as your coffee pot.