Haslett was electrical engineer, electricity industry administrator and champion of women's rights. 

In 1919 she became the first secretary of the women’s engineering society and the founder and editor of its journal, The Woman Engineer. Her key interests lay in harnessing the benefits of electrical power to liberate women from household chores, so that they could pursue their own goals and self-development outside the home.

As a pioneer of women’s engineering, she founded the first women’s engineering first in 1920, became the first director of the Electrical Association for Women in 1924 and the first woman to be made a Companion of the Institution of Electrical Engineers.
In 1947 she was appointed as the first female member of the British Electricity Authority (BEA). The BEA later set up the Caroline Haslett trust to provide scholarships and travelling fellowships for its members. Haslett died in 1957 and as per her will was cremated by electricity.