I have a US electric oven/stove combination with four stove burners, two smaller and two larger. I feel the stove is already a bit anemic so I want to make sure I am getting the maximum energy out of the stove, but I also like using smaller pans on the smaller burner. Do typical US electric stoves put the same amount of total energy (i.e., the same amount of BTUs) through the smaller burners as through the larger burners, or are the smaller burners also lower energy?
Electric stove elements have a different KW rating depending on construction and size
A typical spiral element of 200 mm (8") diameter will be 2 KW, a 150 mm (6") diameter element will be 1.3 KW
Different stove makes and models have different ratings. But not many go above 2 KW
Stove makers usually publish exact specifications on their web sites
1 W is approximately 3.4 BTU
Not only do the small burners have less power, all burners will be colder when used at once.
Here in Europe, it is typical to have large hobs at 2 KW and small ones at 1.5 KW. These are average numbers, different models will have +- 200 W difference.
But the problem is that the electrical wiring of the house cannot deliver too much electricity at once. So the output of a stove is capped at what the wire can provide. If you turn on a single large burner, it will give you the full 2 KW. If you turn on all elements at once, running them at full power may be too much for the line, so modern stoves will internally reduce the power given to each burner, even if you have turned it to the maximum setting. (Old ones will just try to get all the power and your fuse will blow).
I don't remember what the max rating for stoves is, I think 7.2 KW was common when I looked at induction stoves, this could be different for other models (I looked at pure stoves only, which don't have to share the power line with an oven).
For anyone who wonders this about any burner, you can determine it empirically.
With 2 of the same kind of pot or pan, put the same amount of water in each one. If you don't have measuring tools, just fill a cup or glass with water, pour it into one pan. Then do the same with the other pan.
Set your burners both to high. If one boils well before another, you know that burner outputs more BTUs. If the times are pretty close, say within a few seconds, the two burners probably have the same or very similar heat output.
The pot should be larger than both burners, otherwise the larger burner may be putting out a significant amount of heat that doesn't go into the pot.