"Work in a power plant", "work on a power plant" or "work at a power plant"?

Question

Which preposition do I use if I want to say that someone's work place is a power plant? For example:

I work in a power plant.

I work on a power plant.

I work at a power plant.

Answer 1

This is a great question!

The first and third options - "in a power plant" and "at a power plant" - are both correct for this specific example of work, so long as you mean "doing some job inside an existing power plant".

The second option "on the power plant" would mean something different - e.g. that you are an engineer or labourer involved with the construction of a new power plant. For instance:

"I'm a design engineer, and I am working on the power plant == "I am working on the design of the power plant."

However, in other cases, the "on" preposition will be appropriate. The general principle is that:

• "at" or "in" are generally used when the worksite is indoors (e.g. an office, factory, shop, etc), while
• "on" is typically used when the worksite is an outdoor structure (and the work is done largely outside).

The following examples illustrate.

Examples where "in" or "at" are (largely) interchangeable

• "I work in a bank." or "I work at the bank."
• "I work in a factory." or "I work at a factory."
• "I work in a grocery store." or "I work at the grocery store."
• "I work in a power plant." or "I work at a power plant."

Note that in these examples, the "at" preposition will generally be more appropriate where the workplace is a specific workplace (preceded by "the").

Examples where "on" is essential

• "I work on an oil rig."
• "I work on a ship."
• "I work on the rail tracks."

Examples where "on" or "at" are largely interchangeable

• "I work on a construction site." or "I work at a construction site."
• "I work on the wharves." or "I work at the wharves."

Examples where "at" is essential

• "I work at the outdoor vegetable markets."

Answer 2

All three could be used, but they have slightly different connotations concerning the exact workplace of the worker.

I work in a power plant.

The employee's tasks are inside the power plant. (She may be a janitor, but her work is inside the structure.)

I work on a power plant.

The worker's job is constructing or caring for the power plant itself. (He is probably a civil, electrical, or mechanical engineer.)

I work at a power plant.

The laborer's work is located within the property lines of the premises of the power plant. (She may be outdoor security or landscaper or driver and she never enters the power plant, even though she works near it.)

Additionally, one also might say:

I work for a power plant.

The worker's employer is a company that owns the power plant. (He may be a worker from the previous examples or he may be a researcher or manager or salesman who does all his work off-site.)