To find out how much electricity a coffee maker on warm uses you will need to determine the
wattage of the appliance and determine how long the warmer is likely to be used.
To determine the cost of electricity per kilowatt hour in your state, visit the website linked
HERE
or get the cost per kWh from your monthly power bill.
Next, determine the voltage/watts of the the coffee maker. This information can
probably be found on the bottom or back of the machine.
Then use the calculator at the bottom of this page.