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## kilowatt hours and firing costs

### Ivor Townshend on sat 21 jul 01

My 2.6 cu ft kiln uses 26-29 kWhr to fire a full load to Cone 06.

It uses 34-36 kWhr to fire a full load to Cone 9.

These are averages from several firings provided by my computer
which monitors each firing.

Kilowatt Hours are a measure of the energy required to heat up the
load (pots and kiln furniture) and compensate for the losses of heat
energy through the kiln wall and from venting.

Thicker walls and better insulation will reduce the amount of energy
(kWhr) required to do the job. My kiln has 3" walls of modern
lightweight insulating brick.

Faster firing will reduce the energy needed since there is less time
for energy to be lost. My firing times are 10 hours for cone 06 and
rather less for the cone 9 which I fire much faster.

Larger kilns require proportionately rather less energy (kWhr) to
achieve the same effect since they have proportionately less
surface for each cubic foot of load and are therefore more efficient.
It's the surface area that governs the losses. A kiln twice the
capacity will require LESS than twice the energy provided that the
firing time is the same.

Finally your electricity bill will give the cost per kWhr so working
out the cost is simple arithmetic.

You do not need to get involved with volts and amps and
complicated mathematics to obtain a reasonable answer. As
someone else said firings are not expensive. What costs a lot is
the time we devote to our pots and our failures! I wish I could pot
as efficiently as my kiln fires them.

I recommend a good book on electric firing to explain the niceties
of the subject. Harry Frazer, Electric Kilns supplies a lot of the