My home is situated near a large Amish community so I have some insight as to how they choose to live. Like many sects, they have those who choose to live a strict life "the old way" and those who are more contemporary. All have homes with no electricity, and few have them with running water...mainly because it takes electricity to run well pumps. Many do, however, allow propane powered appliances, including refrigerators, in the home.
Those who live on working farms still rely upon horses for the power to pull a plow or wagon, but many have started using gasoline powered equipment like mowers and trimmers as well as generators (to charge the buggy batteries). The rule though is, no power equipment of any kind inside the home.
Becoming more common now in the Amish community is the telephone. It's situated outside in what looks like a kid's school bus stop and is usually shared by several homes in the area.
The lights you see on a buggy are a result of local laws, enacted after fatal wrecks between a buggy and the "English" as those of us in the outside world are called.
At our national in Goshen, IN, several years ago, a fellow KFer and I stopped at an Amish roadside stand and in the course of conversation with the older gent running the place, we came to learn that he knew my family as well as that of the other fellow. Both of us are from the same western PA area with an Amish contingent...proof that the world truly is getting smaller!