The energy costs on production of vegetables in protected area is currently the most talked-about subject of growers from countries with cold climates, where heating cost makes risky business with production of vegetables in greenhouse. The recent surge in fuel costs is decreasing farmers’ profit margins that more than even impose producers to save energy along the production cycle and to look for alternative sources of fuel for heating greenhouses. Moldova has significant amount of agriculture wastes (3.26 mln.t per year) which are co-products on production of agricultural crops: straw, corn and sunflower stalks, trees pruned branches, etc. This can serve as an alternative source of 164 energy for heating greenhouse. This investigation shows the calculations of the heat balance in plastic greenhouse, amount of heat loses through greenhouse cover and soil, amount of sun energy captivated in greenhouse and required amount of artificial energy to grow tomato out of season. Based on this calculation was determined the efficiency of biomass (straw) for heating greenhouse. For production of tomato in January it require an additional artificial heating of greenhouse with capacity of 736 MJ/m2, this energy can be covered by burning 51,7 kg of straw per m2 of greenhouse, comparing with 21 MJ/m2 and 1,5 kg of straw respectively in April.