These days there are all kinds of power/energy meters available which can measure the power consumption and the operating costs of mains powered appliances. A prerequisite is that the appliance has a mains plug. However, if the power consumption is known then the energy use of the appliance can also be determined in a much easier way.
The operating hour counter for mains (230 VAC) appliances described here can measure the following, even in difficult to access places:
1. Number of times that it is switched on and off (up to 99999)
2. How long the load (lamp, fan, etc.) has been switched on (up to 99999:59:59 hours, resolution 1 s).