Since we last did this post electric bills have increased again :( But not to worry, we have recalculated the costs so you don’t have to!
The more in depth calculations are below but here is a quick overview:
Paragon SC2, held at 800C for 30 minutes, will likely cost you less than 25p (£0.23).
Prometheus Pro1, held at 800C for 30 minutes, will likely cost you less than 10p (£0.098).
Prometheus Pro 7, held at 800C for 30 minutes, will likely cost you less than 30p (£0.26).
Every electrical appliance has a power rating which tells you how much electricity it needs to work. This is usually given in watts (W) or kilowatts (kW) (1000W is the same as 1kW). The amount of electricity actually used depends on how long the item's on for, and this is measured in kilowatt-hours (kWh).
The elements of our electric kilns are usually only on for about half to a third of the firing time, as the elements cycle on and off during both the heating and holding period as the kiln adjusts the temperature.
Electric bills are currently capped at 28p kWh for those paying by direct debit so we have re done then calculations based on that cost. Have a look at your bill to see what you're paying, and adjust the calculations below - I've laid them out clearly, so you can easily replace with your own rates.
Let's compare our kilns to some other home items and their average electricity usage (averages have been taken from Centre for Sustainable Energy);
Prometheus Pro1 - 700W
Paragon SC2 - 1650W
Prometheus Pro7 - 1900W
Toaster - 800-1500W
Hairdryer - 2000W
Tumble dryer 2000-3000W
Oven - 2000-2200W
Kettle - 3000W
Electric shower - 7000-10500W
So a SC2 or PRO1 kiln will use about as much electricity as your toaster, less than your oven, kettle, and a LOT less than your electric shower.
Some people recommend firing metal clay for 2 hours. Personally I think this dates back to an old understanding of the original clays, which required this long to fully sinter. The modern versions of silver clay, like Art Clay Fine Silver, will be fully sintered in about 30-45 minutes at 800℃ - any longer than that and no real strength difference was detected in tests. As firing for 2 hours won't make much (if any) difference, my suggestion is to fire under an hour and save some energy!
Here are some examples of our kilns:
Prometheus PRO1 Kiln Firing costs
The Pro 1 kiln is rated 700W. This means it uses 0.7kW per hour when on full. This is A LOT less than most convector heaters or heating fans, which are usually 2000W-2500W.
Say our firing schedule takes about 30 minutes to heat up and then we hold for 30 min, giving us a 60 minute or 1 hour total firing.0.7kW x 1 hours = 0.7kWh
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If we estimate a scenario where the elements are on for half the time of that firing (as they will switch on and off during a firing), the actual energy usage would be:0.7kW (the energy the kiln uses) x 1 hour firing = 0.7kWh / 2 (half the time as elements switch on and off) = 0.35kWh used.
If we estimate the electricity cost to be 28 pence per kWh it would mean 0.35kWh x 28p = £0.098/firing.
So, if you take your Pro 1 kiln to about 800C and hold it there for 30 minutes, it will likely cost around 9.8 pence.
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Paragon SC2 Kiln Firing costs
The SC2 kiln is rated 1650W. This means it uses 1.65kW per hour when on full. This is less than most convector heaters or heating fans, which are usually 2000W-2500W.
Say our firing schedule takes about 30 minutes to heat up and then we hold for 30 min, giving us a 60 minute or 1 hour total firing.1.65kW x 1 hours = 1.65kWh
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If we estimate a scenario where the elements are on for half the time of that firing (as they will switch on and off during a firing), the actual energy usage would be:1.65kW (the energy the kiln uses) x 1 hour firing = 1.65kWh / 2 (half the time as elements switch on and off) = 0.825kWh used.
If we estimate the electricity cost to be 28 pence per kWh it would mean 0.825kWh x 28p = £0.23/firing.
So, if you take your SC2 kiln to about 800C and hold it there for 30 minutes, it will likely cost you less than 25p.
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Prometheus PRO7 Kiln Firing costs
The Pro 7 kiln is rated 1900W. This means it uses 1.9kW per hour when on full. This is less than most convector heaters or heating fans, which are usually 2000W-2500W.
Say our firing schedule takes about 30 minutes to heat up and then we hold for 30 min, giving us a 60 minute or 1 hour total firing.1.9kW x 1 hours = 1.9kWh
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If we estimate a scenario where the elements are on for half the time of that firing (as they will switch on and off during a firing), the actual energy usage would be:1.9kW (the energy the kiln uses) x 1 hour firing = 1.9kWh / 2 (half the time as elements switch on and off) = 0.95kWh used.
If we estimate the electricity cost to be 28 pence per kWh it would mean 0.95kWh x 28p = £0.26/firing.
So, if you take your Pro 7 kiln to about 800C and hold it there for 30 minutes, it will likely cost you less than 30p
