E_assimilated = Δ E_biomass + Δ E_reserves + E_exported + E_metabolically dissipated
This is the cleaner physical balance.
The functional purposes of expenditure—maintenance, movement, defense, reproduction—should then be recorded separately, because summing functional categories and heat without a defined boundary can double-count the same energy.
Operational definition
Accounting partition.
The allocation of the chemical free energy associated with assimilated material among mutually defined endpoint pools over a specified interval.
At the broadest level:
E_assimilated
=
Δ E_biomass
+
Δ E_reserves
+
E_exported
+
E_dissipated
The precise equation depends on the system boundary. Functional expenditures such as movement or defense should not be added to heat without care, because the energy used for those functions ultimately contributes to dissipation and could otherwise be counted twice. Ecological energy accounting distinguishes acquisition, assimilation, respiration, waste, and production rather than treating all consumed energy as incorporated biomass. (OpenStax)