Comparing pottery kilns sensibly means comparing four things in order: the electrical supply they need, the internal dimensions, the top temperature and the controller. Price follows from those rather than leading them, and a cheap kiln you cannot power or fill is not cheap.
Supply first
A kiln that runs from a thirteen-amp socket can be delivered and used the same day. Anything above about three kilowatts needs a dedicated circuit and an electrician, which adds cost and, in rented accommodation, a conversation with a landlord. This single question eliminates most of the market for most buyers and should therefore come first.
Internal dimensions, not litres
Volume in litres tells you little, because a tall narrow chamber and a wide shallow one of the same volume fire completely different work. Measure your largest realistic piece, add the shelf thickness and prop height beneath it, and compare that against the internal height and diameter. Kiln listings publish both.
Top temperature and margin
Earthenware needs around 1150, stoneware around 1250, porcelain higher. A kiln rated barely above your working temperature will spend its life at full stretch and its elements will age quickly. A margin of a hundred degrees or so costs little at purchase and pays for itself in element life.
Then price, and running cost
The purchase price is the visible number and the electrical installation is the hidden one. Running cost is calculated from the kilowatt rating, the length of the schedule and your tariff rather than read off a page, and a glaze firing in a full kiln is far cheaper per pot than the same firing half empty.
Questions people ask about pottery kiln
How do I compare kiln sizes?
By internal dimensions against your largest piece plus shelf and props, not by volume in litres, which hides the shape of the chamber.
What temperature rating do I need?
Around 1150 for earthenware and 1250 for stoneware, plus a margin. A kiln working constantly at its limit wears its elements quickly.
What does a firing cost?
Calculate it from the kilowatt rating, the schedule length and your tariff. A full kiln is far cheaper per pot than a half-empty one.