One of the main obstacles to transfer to carbon neutral energy management is technological transition. An important task is to change fuel used in the boiler furnace from natural gas (fossil fuel) to biomass. The easiest but most expensive solution is the installation of a biomass boiler. Other solutions include burner replacement or additional installation, but these options are more complex from an engineering and technical point of view. By replacing natural gas with wood particles, boiler output is reduced, because the value of combustion heat, furnace load and specific combustion parameters are lower, as well as the temperature and pollution with nitrogen oxides NOx decrease. If energy end user improves energy efficiency and reduces energy consumption the possible reduction in boiler output as a result there can actually be excess installed capacity in the boiler house. The feasibility of co-firing is calculated with levelized cost of energy analysis.