Stove element wattage does differ from model to model and some glass tops will cycle the element to protect itself.
If you have an older stove you can change out the element for a 2600W (the highest available) for under $15. Older stoves can vary from 2000W to 2600W for the large burner. This is a difference of 6824 BTU to 8872 BTU. Propane burners are 30,000 BTU or so, but do loose a lot to atmosphere.
Arron - quality over quantity beer drinker