Himalayas with diverse topographical and ecological zones sustain diverse agroecosystems. Differences in precipitation regimes, cropping systems, land-use systems and availability of resources significantly affect energy flow within agroecosystems (AGEs) of the region. Thus, the present study was aimed to evaluate the energy use pattern and economic profitability of different sized agroecosystems (small, medium and large) along the altitudinal gradient [very low altitude (VLA), low altitude (LA), mid altitude (MA) and high altitude (HA)] of Central Himalaya, India. The sampling was carried out following random stratified design and total 108 agroecosystems (4 altitudes× 3 sizes × 3 replicates × 3 seasons) were assessed. Data collected on quantities of agricultural inputs and outputs were converted to energy values using standard energetic constants and monetary values on the basis of local market price. Low altitude agroecosystems predominantly support cereal + pulse based cropping systems while, high altitudes favour cash crop cultivation (vegetables). Significant variation (P < 0.05) in total input and output energy was observed seasonally, while differences were insignificant across sizes and altitudes. Irrespective of the sizes and seasons, farmyard manure (organic fertilizer) contributed major share of total energy inputs across all altitudes in the order: HA _AGEs (66.7 %) > MA _AGEs (66.1 %) > VLA _AGEs (62.6 %) > LA _AGEs (52.1 %). The share of non-renewable energy inputs (inorganic fertilizers and fuel) declined along altitudinal gradient as: LA (31.1 %) > VLA (26.9 %) > MA (12.5 %) > HA (11.8 %). Seasonally, highest net energy was recorded during rainy season (92286 M J ha⁻¹ yr⁻¹) followed by summer (68906 M J ha⁻¹ yr⁻¹) and winter (18686 M J ha⁻¹ yr⁻¹). The economic yield significantly increased with increasing altitude and was recorded maximum for large sized agroecosystems. Energy use efficiency (EUE) differed distinctly (P < 0.05) across seasons and was recorded maximum during rainy season (8) while, across sizes and altitudes it did not vary significantly. EUE did not reflect any definite pattern along altitudinal gradient [HA _AGEs (3.84) > VLA _AGEs (3.81) > LA _AGEs (3.56) > MA _AGEs (3.01)]. Benefit-cost ratios (BCR) differed significantly (P < 0.05) along altitudes and was maximum at VLA _AGEs (5.27) however, differences were insignificant across sizes and seasons. From present study, it can be concluded that season and altitude had significant impact on the energetics and economic flow of the agroecosystems while, no marked differences were observed for size classes. High altitude agroecosystems were energetically efficient while, monetary wise very low altitude systems.