Heat transfer has the dimension mass per time cubed thermodynamic temperature. The SI composite unit of heat transfer is the kilogram per second cubed kelvin.

Maple knows the units of heat transfer listed in the following table.

An asterisk ( * ) indicates the default context, an at sign (@) indicates an abbreviation, and under the prefixes column, SI indicates that the unit takes all SI prefixes, IEC indicates that the unit takes IEC prefixes, and SI+ and SI- indicate that the unit takes only positive and negative SI prefixes, respectively.  Refer to a unit in the Units package by indexing the name or symbol with the context, for example, tog[standard]; or, if the context is indicated as the default, by using only the unit name or symbol, for example, tog.

The units of heat transfer are defined as follows.

A standard U factor is defined as  international table Btu per hour square foot degree Fahrenheit.

An SI U factor (USI) is defined as  watt per square meter kelvin.