How Much Does It Cost to Fire My Kiln?
It is good business to know your costs. Firing costs have always been somewhat of a mystery to many ceramic artists. While there are many variables that can affect the cost, the calculation is actually fairly easy. The new Skutt controller will actually calculate it for you after each firing and if you have KilnLink, it will automatically store those costs on your own personal “MySkutt” page. If you are working with an older kiln and do not have this feature you can easily calculate it using this formula.
KW Rating of Kiln x Length of Firing (Hours) x $/KW/Hr x Adjustment Factor = Cost of Firing
Example: KM1231PK 208V 1 PH kiln firing a Medium Speed ConeFire Mode Program to Cone 6 using a USA average electrical rate of $0.12 KW/Hr and a load 100 lbs in the kiln.
16.64 x 8.47 x .12 x .5 = $8.45
So $8.45 to fire one of our largest kilns with a full load to CONE 6! A lot less than most people think. A model 818 fired to Cone 06 was only $2.83. Now I know that a lot of you are pretty observant and are going “hey. what is this mysterious Adjustment Factor?” In order to better understand this we need to look a little closer at all of the variables individually. You will see why this number is a sort of best guess due to the variability of variables.
Wattage
This one is pretty straight forward. If you look on the serial plate on your control box one of the pieces of data is the Wattage rating of the kiln. This is the amount of energy that particular model uses when it is brand new and on 100% of the time for 1 hour. Since you are charged in Kilowatt hours, and this number on the control box is listed in wattage hours, you need to divide this number by 1000 before plugging it into the formula.
As your elements age they lose some of their power so this number will slowly drop as your elements age. This number is also based on having the exact voltage of the rating of the kiln available, under load (while kiln is on), during the entire firing. The odds of this happening is pretty slim, but if you installed the kiln correctly, it should be close. Here are some of the things that can affect your wattage:
- Low Voltage Caused by Undersized Wire or Undersized Transformer (you live at the end of a country road)
- Low Voltage Caused by Over Use of the Power Grid (everyone using their air conditioning on a hot summer day)
- Worn Out Elements
Firing Times
There are many things that can affect the time amount of time it takes your kiln to fire a particular program. The good news is that the kiln keeps track of this and tells you how long it took after every firing. You will notice that this number will vary. Just because you tell the kiln to follow a particular program, does not mean it is capable of following the program throughout the entire firing. Because of this, the firing times will vary on the same program. Here are a few things that can affect your firing times:
- The Size of the Kiln Load
- The Temperature You Are Firing To
- The Temperature of the Kiln Room
Price of Electricity
The cost of electricity varies all over the nation. It is usually affected by the amount of locally generated power available to a given population. Because some areas have less than power than they would like, they ration it out by charging different rates based on when you use it or what type of consumer you are. You may want to see if you get lower rates if you fire at night. If you are estimating the cost of firing your kiln in a commercial building, be sure to use the rate listed on the businesses energy bill and not your one at home. Rates can vary between $0.08 (Washington) and $0.38 (Hawaii) per kilowatt hour with the USA average being at $0.12/KW/HR for residential and $0.10 for commercial.
Adjustment Factor
The nice thing about the new Cost calculation feature in the new KilnMaster Controller (manufactured after July 2012), is that it actually calculates how long the elements are actually on. As you probably know from hearing the relays clicking, they cycle on and off to achieve the correct firing rate. The frequency of this cycling will depend on the program entered and the ability of the kiln to follow the program entered. Programs that have fast firing rates or that approach the maximum temperature rating of the kiln will generally require the relays to stay on longer. Conversely, programs with extended hold times will require less “on time” for the relays. Obviously when your relays shut off power to the elements, you are not incurring any cost so this “off time” needs to be accounted for. We have found that a good estimate, across the range of ConeFire Mode programs, is 50%.
If you have a KilnMaster kiln manufactured after July, 2012 you can Click Here to find out how to configure it to calculate your firing costs.
