Uncertainty remains regarding the effect of excess dietary protein on the energetic cost of urea excretion in beef cattle. We individually fed British-cross steers (n = 27; initial BW = 350 ± 32 kg) a finishing diet based on steam-flaked corn (14.4% CP) top dressed with commercially-available condensed tannin extract (CT) at 3 levels (0, 0.5, and 1.0% of diet, DM basis). Ruminal methane (CH₄) and metabolic CO₂ fluxes were measured using a GreenFeed unit (C-Lock Inc., Rapid City, SD) for two 20-d sampling periods, that coincided with fecal and urine sampling. Diet digestibility and N balance were estimated approximately 30 d after the experiment began (EARLY) and 30 d before the animals were harvested (LATE), using TiO₂ as a marker of fecal output and urinary creatinine:BW ratio as a marker for urine output, respectively. From this, we previously determined that fecal N excretion as a percentage of total N excretion increased approximately 10% as CT supplementation increased to 1.0%. Urine energy loss was estimated from urine N excretion, assuming all excreted N was urea. Heat production was estimated from the Brouwer (1965) equation. Oxygen consumption was estimated from CO₂ production assuming a respiratory quotient of 1.05. Flux of CO₂ (10,279, 10,537, and 10,478, g/d; SEM: 542.5) and CH₄ (144, 154, and 158 g/d; SEM:13.2) were similar (P ≥ 0.23) among treatments during both sampling periods for 0, 0.5, and 1.0% CT, respectively. Percentage of GE intake lost as CH₄ was not different for 0 (3.27%), 0.5 (3.32%) or 1.0% (3.71%) CT. Proportion of GE intake lost in urine averaged 1.03, 1.01, and 0.97% for CT levels of 0, 0.5, and 1.0%, respectively but was not different among treatments (P ≥ 0.41; SEM: 0.08). Heat production was similar across treatments (27.3, 28.0, 27.8 Mcal/d; P ≥ 0.52; SEM: 1.37) and no difference was observed for heat production lost as a percent of GE intake (47.0%, 45.7%, 50.1%) for 0, 0.5, and 1.0% CT, respectively. The results of this study suggest that while N excretion was altered by 10% from urine to feces by tannin supplementation, no difference in energy losses was observed.