The thing that was most important about electricity in the 1920s was its ability to transform the lives of the people who were able to get it. During this decade, electric power became very common in cities. The link below says that about 85% of all homes in cities had electricity by 1930.
Electricity made life much easier. For example, it allowed women who worked in the home to use vacuum cleaners instead of having to beat their rugs by hand. It also made life more fun. For example, it allowed people to listen to radio shows -- a major form of entertainment during this time.
So, overall, electricity was important because it improved the lives of Americans, especially in the cities.