The subsidy consists of a deduction from IRPEF or IRES and is granted when interventions are carried out that increase the level of energy efficiency of existing buildings. In general, deductions are recognized for: the reduction of energy requirements for heating thermal improvement of the building (insulation - floors - windows, including fixtures) the installation of solar panels the replacement of winter air conditioning systems. The deduction is also due for the purchase and installation of solar shading; the purchase and installation of winter air conditioning systems equipped with heat generators powered by biomass fuels; the purchase, installation and installation of multimedia devices for remote control of heating systems, hot water production or air conditioning of housing units; the purchase and installation of micro-cogenerators to replace existing plants; the purchase of condensing hot air generators; the replacement of winter air conditioning systems with hybrid appliances consisting of a heat pump integrated with a condensing boiler The deductions, to be divided into 10 annual installments of the same amount, vary depending on whether the intervention concerns the single real estate unit or condominium buildings and the year in which it was made. An indispensable condition for benefiting from the facility is that the interventions are carried out on existing real estate units and buildings (or parts of buildings), of any cadastral category, even if rural, including those instrumental for business or professional activities. The relief can be requested for expenses incurred by 31 December 2020. For most of the interventions the deduction is equal to 65%, for others it is 50%. In particular, from 1 January 2018 the deduction is equal to 50% for the following expenses: purchase and installation of windows including fixtures and sun screens replacement of winter air conditioning systems with systems equipped with condensing boilers with an efficiency at least equal to class A of the product (from 2018, systems equipped with condensing boilers with an efficiency lower than class A are excluded from the subsidy). On the other hand, if in addition to being in class A they are also equipped with advanced thermoregulation systems, the highest deduction of 65% is recognized. purchase and installation of winter air conditioning systems equipped with heat generators powered by biomass fuels.