Good morning Dave,
The 900 watt coffee maker takes 900 watts to operate. At 120 volts it would use 7.5 amperes when operated. Watts = volts X amps so watts/volts =amps. Actually watts per hour means watts/hours. The term kwh means kilo watts x the number of hours. (I believe mph means miles/hours: ex. 600 miles in 10 hours = 600/10 or 60 mph) For kwh ex 900 watt coffee maker used for 24 hours straight; 900 watts x 24 hrs = 21600 watt hrs or 21.6 kwh.
I believe that appliances are rated in watts, not watts/hours. The terms 900 watts per minute or second or day also are a problem. If the product works for 15 minutes is power consumption would be 900 watts x .25 hrs = 225 watt hrs or .225 kwh. Another example is the rating of the wind farm in my area is 300 megawatts. Its actual power output is billed in kwh or megawatt hrs.
My wife and I wrote a couple articles for a sailing magazine a few years ago and though they weren't dealing with electricity the guidelines of the editor made it clear that if something was submitted and described powers as watts per hour that he wasn't interested.
Realized that this may seem like babble so here is what wikepedia has to say:
Watt - Wikipedia, the free encyclopedia
Confusion of watts, watt-hours, and watts per hour
Power and energy are frequently confused. Power is the rate at which energy is generated and consumed.
For example, when a light bulb with a power rating of 100W is turned on for one hour, the energy used is 100 watt-hours (Wキh), 0.1 kilowatt-hour, or 360 kJ. This same amount of energy would light a 40-watt bulb for 2.5 hours, or a 50-watt bulb for 2 hours. A power station would be rated in multiples of watts, but its annual energy sales would be in multiples of watt-hours. A kilowatt-hour is the amount of energy equivalent to a steady power of 1 kilowatt running for 1 hour, or 3.6 MJ.
Terms such as watts per hour are often misused.[8] Watts per hour properly refers to the change of power per hour. Watts per hour (W/h) might be useful to characterize the ramp-up behavior of power plants. For example, a power plant that reaches a power output of 1 MW from 0 MW in 15 minutes has a ramp-up rate of 4 MW/h. Hydroelectric power plants have a very high ramp-up rate, which makes them particularly useful in peak load and emergency situations.
Major energy production or consumption is often expressed as terawatt-hours for a given period that is often a calendar year or financial year. One terawatt-hour is equal to a sustained power of approximately 114 megawatts for a period of one year.
I think my point is kwh is a product of watts multiplied by time and this is what we are charged for and watts per hour is division which does not apply to our use.
Does this make any sense?
Loren