The aim of the study was to compare energy partitioning between heat production (HP) and retained energy, and efficiency of dairy cows fed with different strategies during early lactation. At calving, 18 primiparous cows (528 ± 40 kg BW; 3.2 ± 0.2 BCS; fall calving) were assigned in a randomized block design to either (G0) total mixed ration (TMR) ad libitum (55% forage: 45% concentrate; offered 17 kgDM/d) or (G1) grazing of alfalfa (6-h grazing in 3-d strips; 20 kgDM/d) + 70% of ad libitum TMR intake (12 kgDM/d) during 65 d postpartum. All cows consumed at each milking, 2.0 kgDM/d of a grain-soybean meal concentrate. Cows were milked twice a day; milk yield was measured daily, milk composition once a week, and BW and BCS every 14 d. The HP was measured by the O2-pulse technique at 42 ± 3 d postpartum, and retained energy in milk and in body tissue (estimated from BW and BCS changes) were used to calculate energy balance from 29 to 57 ± 3 d postpartum. Metabolizable energy (ME) intake was estimated as HP + total retained energy. Residual HP was calculated as the difference between measured and predicted (based on NRC coefficients) HP. Data were analyzed with a mixed model including treatment as fixed and block as random effect. Milk yield tended to be greater (P = 0.09) for G0 than G1 cows, while its composition was not affected by treatment. Cow BW did not differ but BCS was greater for G0 than G1 cows (P = 0.01; 2.9 vs. 2.6 ± 0.06). Total retained energy was greater for G0 than G1 cows (P < 0.01; 92.7 vs. 84.8 ± 1.7 MJ/d) as both, energy in milk and tissue, were greater (P ≤ 0.04) in the former ones. Whole-animal HP (90.7 vs. 94.4 ± 4.0 MJ/d) and calculated ME intake (182.2 vs. 179. Seven ± 4.8 MJ/d) did not differ between G0 and G1 cows. Residual HP (as % of ME intake) tended to be 10% less (P = 0.06) for G0 than G1 cows. Adjusted energy efficiency tended to be greater for G0 than G1 cows (P = 0.08; 0.51 vs 0.47 ± 0.01). Results indicated G0 cows were more efficient, secreting more energy in milk and retaining more energy in body tissue, as maintenance requirements increased around 10% by the inclusion of grazing in G1 cows.