Your dad must be a tightwad. A small desk fan won't even be noticeable on the electric bill.
I'd say at the high end your little fan will cost about $1.00 a month to run if you run it 24/7 depending on electric rates.
But I'm sure it will probably only cost around 25 cents per month. Even $1.00 a month would be cheap to run it.
The fan will cost you more to purchase.