How do I tell guest that there is a propane charge?

[Sally27]

My guests are eating up all my profits with the use of the spa.  How do I let them know that there is a propane charge for use of the spa.  Approximately a 35 $ charge per weekend.  Propane is expensive and the guests heat the spa when no one is in it.

[Fleur--Dan-And-Kids0]

One of your reviews actually mentions that you were kind enough to have a warm tub waiting for their arrival.  As a guest if i found out later that this was at an additional cost i would be pretty annoyed.  You need to put this price into your daily fee to cover it.  I see no mention anywhere that you charge additional.  By the look of the reviews and description i'd assume it was part of my daily fee.