But how can you determine how much electric potential energy a system has, and how much work it can do?

但是如何确定势能的大小 什么系统，能做多少工作？

At the same time, solar energy, electric vehicles, were just starting to come into their own, and it was actually cheaper to use these than burn oil.

与此同时， 太阳能、电动汽车等才刚刚开始普及，使用这些实际上比烧油更便宜。