You’re really talking about a “typical retail business” as opposed to a “typical business”.
This isn’t something best looked at in terms of a percentage. Because salaries and employment costs are the largest overhead, two identical scenarios where one store has three employees and the other has two would produce two very different percentage of overheads occupied by utilities despite the cost of utilities being the same. It’s a bit of a nonsense statistic, basically, when looking at a small business.
All of this said, you would expect no more than 2–10% of overheads would be utilities for a single (not a chain) retail store with 4 or 5 employees including the owner.
Hope this helps!