The energetic cost of endothermy

Defending a setpoint is not free: the restoring flux that holds the basin against an ambient drive rises with loop gain (True). A resting endotherm therefore idles at a much higher metabolic rate than an equal-mass ectotherm at the same body temperature -- a cited factor of roughly 5-10x. The absolute rate is open.

RT3. The trade-off is structural: thermal stability is bought with continuous restoring flux. The R19 loop reproduces the DIRECTION (cost rises with defense); the MAGNITUDE (~5-10x resting metabolic rate) is cited [L]; absolute W/kg is [O] and needs external calorimetry.

Stability costs flux

In the loop, a deeper basin resists drive but demands more restoring flux to hold position against it. That flux is the metabolic price of a defended setpoint. The model gives the sign and the monotonicity, not the watts.

The cited range (Q3, part 1)

~5-10x: a resting endotherm idles at roughly 5-10x the metabolic rate of an ectotherm of the same mass and body temperature. [L] cited (e.g. Bennett & Ruben 1979; Else & Hulbert 1981). Absolute W/kg is [O].

Honest open

Absolute W/kg is [O]: the obstacle is that the R19 restoring flux is in model units, and mapping it to metabolic power needs an external calorimetry calibration the substrate does not contain. The ~5-10x factor is carried as a CITED measurement, not a derived number.