What BTU Actually Tells You
BTU measures how much heat a grill can produce in an hour. It says nothing about how evenly that heat reaches food. A 36,000 BTU three-burner and a 74,000 BTU five-burner are not better and worse - they are sized for different cooking areas.
The number on its own is meaningless
BTU per hour is fuel burned, not food cooked. Spread 36,000 BTU over a small grate and it is fierce; spread the same figure over a large one and it is moderate. The useful figure is output divided by cooking area, and almost nobody publishes it.
What actually decides the cooking
Burner count. Three independently controlled burners give a hot zone and a cool zone, which is how anything thicker than a burger is cooked: seared over direct heat, finished beside it. A single huge burner cannot do that at any output.
Grate material. Thin steel drops temperature the instant cold food lands on it. Cast iron holds heat and returns it, which is what makes the marks and the crust. Porcelain-enamelled cast iron adds a surface that cleans more easily.
Lid and body. Heat that escapes is heat not cooking. A grill that holds temperature with the lid down does more with less.
Reading the two grills here
The three-burner at 36,000 BTU is 12,000 per burner across a domestic grate - the configuration most households cook on. The five-burner combination at 74,000 BTU is not twice the grill; it is a larger cooking area plus a griddle and a pizza oven, and the output is sized to heat all of it.
Questions
What does BTU mean on a grill?
British Thermal Units per hour - how much heat the burners can produce. It does not describe how evenly that heat reaches food.
Is a higher BTU grill better?
Not on its own. Output spread over a larger cooking area is not more intense, and burner count and grate material matter more.
How many BTU do I need?
Think in burners rather than BTU. Three independently controlled zones cover ordinary cooking; five suit a large surface with a griddle.
Why do cast iron grates matter?
They hold heat when cold food lands, where thin steel loses it.