The only way to figure this out accurately is to have a kilowatt meter installed in the power supply line. Each firing is different depending on how the kiln is loaded and the age of the elements.
The next most accurate way would be to sit by it and time it. This will be tricky though- it will require 3 different stop watches and perhaps 2 assistants. If you press the #8 key while firing an automatic kiln, the display will indicate which sections of the kiln are on. It does this by flashing a different dot on the bottom of the screen for each section that is on, top, middle, bottom; the dot on the far left is the top, the dot next to that is the middle, and the dot next to that is the bottom. So one stopwatch for each dot- just keeping track of when each dot is on... you could time it for 10 minutes every hour and get a pretty good idea...
Another Estimation Method
- First look for the watt or kilowatt rating on the kiln. For example an E23T is 11,520 watts. 11,520 watts is about the same as 11.5 kilowatts.
- Next decide how long the firing takes to heat to the top temperature- how many hours. For low fire divide the total hours into 3 equal parts, for high fire divide the total hours into 4 equal parts.
- The first part of the firing for low fire and high fire uses 25% of the KW rating per hour.
- The second part of the firing for low fire and high fire uses 50% of the KW rating per hour.
- The third part of the firing for low fire and high fire uses 75% of the KW rating per hour.
- For high fire the last part of the firing uses 100% of the KW rating per hour.
- Add all these KW numbers up to get the total number of kilowatt hours for the firing.
- Look on your bill to see what you pay per kilowatt hour and multiply cents per hour times the number of kilowatt hours.
- An E23T is 11520 watts or 11.5 KW or basically 11.5 KW are produced by this unit in 1 hour.
- Firing is 12 hours long to cone 6.
- 12 hour long firing gives you 4 equal parts; each 3 hours long.
- 11520 divided by 4(the equal parts) is 2880 or 25% of the watts.
- 2880 watts per hour in the first 3 hours is 8640 watts for the 3 hours of the first part.
- The second part is 50%- just double the 8640 (from the first part’s 25% watt amount) to get 17280 watts for the 3 hours of the second part.
- Third part is 75%- just add 8640 (25%) to the 17280 (50%) to get 25920 watts (75%) for the 3 hours of the third part.
- Fourth part is 100%- just use the watt rating of the kiln; 11520 watts for 3 hours is 34560 watts
- Add all the watts up: 8640+ 17280+ 25920+ 34560 equals 86400 watts for the firing or 86.4 KW or 86.4 kilowatt hours for the whole firing.
- Look on your bill to see what you pay per KWH and multiply- 9 cents per KWH would be .09 x 86.4- would be $7.78 per firing.