I don't think anyone actually uses these
To be quite honest AGAs look fantastic in an old British or Irish home that has a 200 year old kitchen with flagstone floors.
However, the reality of it is that hardly anyone who actually buys one of these beasts actually uses them to cook. Just like an ornate fireplace they're just a peice of furnature. You'll find most people who do buy them also buy an extremely expensive induction hob (cooktop) and the latest, fanciest and most expensive oven do most of their cooking on that.
I've seen these machines in action in modern country houses in Ireland and their primary use was to heat water for radiators and the hot water storage cylinder.
AGA and Waterford-Stanley (their irish equivilant) ranges that I have seen here were fired by either oil or gas. They have a large boiler in the back that heats water that circulates around the radiators and are thermostatically controlled. However, the cooking surfaces and ovens are not thermostatic per-se.. but you can adjust dampers and watch the temprature guage on each oven door to adjust the temp. They're old but they're not totally primative either!
They had the added benefit of looking rather quaint and traditional, heating the kitchen and providing an extra cooking facility should you feel the sudden urge to put on a slow cooked stew or slow roast 4 pheasants simultaniously!
If you're one of the "two fat ladies" cooking duo or one of their die hard fans, these AGA ranges are an absolute must have item! Those two ladies (on of them RIP) absolutely swore by them!
In all of those old kitchens 99% of the cooking was done on a modern gas or electric stove.
In the old days those ranges (stoves) were fired with coal or, in Ireland turf in rural areas. They pretty much were kept burning 24/7 all year and were a very effective form of cooking and quite high tech for the 1800s!
They create a really nice cozy warm feeling in the kitchen and the stone floor gets very pleasantly warm.
People have a nostalgic association with the sense of a cozy kitchen and the smell of slow cooking stews, meats, breads etc..
I would agree, in warmer climates an AGA would be utterly impractical. They were designed for use in the British Isles.. unless you live in Newfoundland don't buy one!
Also, if you're considering a coal fired version.. you might also consider getting a chamber maid!
These machines were designed for the days when a large house had several staff (maids, buttlers etc) and it was normal to have a fire place in every room (including the bathrooms) so a maid spent her entire day going from room to room tending fires!
They've been automatic and oil/gas fired for well over 100 years.. so there's no real reason to resort to an appliance that hasn't been in common use since the mid 1800s ...
They're simply style icon! It's a bit like owning a horse or something you're not likey to ride it to work and park it in multistory parking garage!!