The only standard that I know of seems to be that high is spelled “hi” and low is spelled “lo.”
In between “hi” and “lo,” my gas range has the digits 2 through 9 , but the numbers indicate nothing whatsoever about temperature. The labels “hi” and “lo” and the numbers 2 to 9 refer not to the temperature but the rate at which the burner is generating heat.
There is a lot of confusion about the words heat and temperature in the food world, so maybe it’s “hi time” for me to give you the “lodown.”
First of all, heat and temperature are two different things. Heat is a form of energy, distinct from gravitational energy, electrical energy, energy of motion (kinetic energy), or nuclear energy. It is, in fact, the ultimate form of energy into which all other forms eventually degenerate.
Cooking employs heat to cause physical and chemical changes that we hope will improve the food’s tenderness, digestibility, and flavor. It should come as no surprise that when a food (or anything else) absorbs heat, it gets “hotter,” meaning that its temperature rises. But what is temperature? It’s nothing more than a convenient number invented by humans to indicate how much heat energy a substance contains. In cooking, specific changes take place when a food reaches specific temperatures, that is, when the food acquires enough heat relative to its size. You might say that temperature measures the concentration of heat in a substance.
So it’s the temperature of the food, not the temperature of the gas flame or electric burner beneath the pot or pan, that matters to the cook. The burner is there only to pump heat into the food, no matter what its own temperature may be while doing it. We could place a white-hot poker beneath a frying pan, but it would be a terribly inefficient way to heat the food in the pan.
Then why do we say that one burner at a given setting is “hotter” than another? It’s just loose talk; we don’t really mean to imply that its temperature is higher. We mean only that that burner pumps out heat at a faster rate than the other one, thereby raising the food’s temperature, and cooking it, faster. Instead of “hi” and “lo,” then, we should really label the burner settings “fast” and “slow” (or, inevitably, “slo”).
Different burners, whether gas or electric, do indeed pump out heat at different rates. We measure those rates in Btu’s per hour. A BTU, or British thermal unit, is an amount of heat energy, just as a calorie is. (A nutritional calorie happens to be almost exactly equal to four Btu’s.) But what’s important about a cooktop burner is how many Btu’s or calories it can pump out per minute or per hour. The number of Btu’s pumped out per hour is a good indication of how fast a burner will heat and cook our food. A candle, for example, gives off a total of about 5,000 Btu’s of heat over a period of a few hours, but that’s hardly fast enough to cook with, because its Btu-per-hour rate is pathetic.
Most people, including appliance salesmen and cookbook authors, either are too lazy to say “Btu’s per hour” or don’t know the difference, so they (as you did in your question) speak simply of Btu’s” as if they were a measure of heating speed. But as Tony Soprano would say, wha’y’gon’do?
A home gas or electric range burner may put out between 9,000 and 15,000 Btu’s per hour at their maximum settings. Check the literature that came with your range or contact its manufacturer to find out the ratings of your burners, and you’ll know which ones are hotter (whoops! I mean faster).
In cooking, what ultimately counts is how fast the temperature of the food rises to its optimum cooking temperature and how steadily it will remain there at different burner settings. But alas, the burner’s setting can be only a rough guide, because no matter what its Btuper-hour rating, most of the heat it generates goes into heating up the kitchen.
Experience with a given cooktop will teach you approximately what each combination of burner and setting can accomplish. But good cooks simply keep an eye on what the food itself is doing, continually judging whether more or less heat is called for and adjusting the burner accordingly.
Life is tough.