Denise: are you getting the $25 cost from the COST function on the kiln? Just trying to figure out why my kiln is estimating costs so much lower. I fire to ^6.
When you calculate the cost of your electricity, make sure you're looking at your bill correctly. On my electric bill there are two different main charges, and several other small charges which go into the total- Supply Charge, Delivery Service, Taxes, etc. So if I just look at the cost per KWh, it won't be accurate. You have to take the total cost on the bill and divide it by the KWh used that month to give you the true cost of firing. That said, the cost of electricity can vary greatly around the country. Last time I checked, for it was just under 17 cents per KWh. I estimate my big 21 cubic foot electric to cost me around $35 per load, and I can get electric bills of close to $500 a month for my shop in the winter when the baseboard heaters are running, too. Thank God for budget billing! A 10 cubic foot kiln like a Skutt 1227 I would expect to be in the $12-20 range depending on where you live. A little 1 cubic foot test kiln should only cost a couple of dollars, so within 100 firings you could make up the cost over firing the big kiln empty.
Whether you end up getting a little test kiln or fire the big one empty, you'll need to put in a cooling cycle. An empty big kiln or a little test kiln will cool much slower than a full big kiln, and that will dramatically affect your glazes. It doesn't necessarily have to be a 'slow' cooling, but something that will be consistent in all firings. You should set it to cool from the peak temperature, since crash cooling from the top will also be different in each situation. I cool at a rate of 175/hr down to 1500F, which takes about 3 hours. My big kiln hardly clicks on at all during that cycle once it gets down a couple hundred degrees, and I get identical results from all 3 of my kilns. My test kiln cools so quickly that many glazes come out really bad if I don't slow down the cooling.