In Plain English
Quick Answer
The standard unit for measuring heating and cooling energy in HVAC systems.
Definition
Definition
British Thermal Unit, the standard unit of heat energy used in the United States HVAC industry. One BTU is the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. HVAC equipment capacity is rated in BTUs per hour (BTU/h) or thousands of BTUs per hour (MBH), and cooling capacity is often expressed in tons (1 ton = 12,000 BTU/h).
Context
Why It Matters in Bidding
BTU and ton ratings drive HVAC equipment selection and pricing, so estimators must match the scheduled capacities on the mechanical drawings to the units they quote. Misreading BTU/h or ton sizing leads to ordering the wrong equipment, which carries different costs, electrical loads, and lead times that can disrupt both the bid and the schedule.
Example
Example
Pricing a rooftop unit package, the estimator converts the engineer's 60,000 BTU/h cooling requirement to 5 tons and confirms the quoted RTU model matches before locking in the mechanical sub's number.
See Also
Related Terms
FAQ
Questions Contractors Ask
How do BTUs convert to tons in HVAC estimating?
One ton of cooling equals 12,000 BTU per hour, so a 5-ton unit provides 60,000 BTU/h. Estimators use this conversion to match the capacities listed on the mechanical equipment schedule with manufacturer model ratings, since drawings may express cooling in tons and heating in BTU/h or MBH.
Why does BTU rating matter when pricing HVAC equipment?
Equipment cost scales with capacity, and BTU/h ratings determine which model, electrical service, and accessories are required. Quoting a unit one size off changes material cost, the connected electrical load, curb and ductwork sizing, and lead time, all of which affect both the mechanical bid and coordination with other trades.
What is MBH and how does it relate to BTU?
MBH means thousands of BTU per hour, so 80 MBH equals 80,000 BTU/h. Engineers commonly use MBH on schedules for boilers, furnaces, and heating coils to keep numbers compact. Estimators should read the schedule's units carefully to avoid an order-of-magnitude error when sizing and pricing equipment.
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