Some take-aways I discovered when looking at the arclight.com website on the desktop:

• After a failed search,  provided closest options rather than saying “no results found”
• Indicate where I am in the buying process, Like Jakob Neilsen’s Heuristics: Visibility of system status
• When I get an error message in a purchase, indicate what fields are required by an asterisk so I know I which fields I must fill out