Watts is how much power it draws. A watt is the voltage of the motor times the amount of amps it draws. What you pay for from the electric company are killowatt/hours. Your mag 9.5 running for one hour would draw .093 kwh of electricity. So over a 24 hr period it draws 2.23 kwh.
If you wanted to figure out how much electricity your tank was drawing you would take the watts of each piece of equipment and divide it by 1000 to get killowatts. Then you would multiply the killowatts by the number of hours everyday that said eqipment was running. Once you add up all your equipment you would have a daily draw for your tank. You could then multiply it by 30 to get monthly draws if you wanted too. HTH.