The aim of this thesis was to study alternative energy efficiency improvement systems alongside the current energy system for a 5,500 m² furniture factory. The aim was to find the most energy-efficient and cost-effective solution from the various options. In addition to the current system, a heat pump, ventilation, solar PV and hybrid system were selected as alternative energy systems. Ventilation has an additional supply air and exhaust air system with heat recovery to replace the current exhaust air system. The hybrid system included two energy systems, a heat pump and a solar PV system.

Energy calculations were performed using CAD design software and the Riuska simulation program. Current and alternative energy systems were simulated and the results compared to current energy use. This identified the most energy-efficient systems. Life-cycle costs were calculated for the schemes, which determine the repayment period, net present values and internal interest rates of the schemes. Ready-made Excel templates were used in the life cycle costing.

The hybrid system is the most energy-efficient system, which reduces the total energy consumption by 96.9 MWh per year. The second most efficient system is heat pump-system, which reduce the total energy consumption by 71.3 MWh per year. Due to the dimensioning of solar PVs, the total energy consumption reduces by 25.6 MWh per year. The ventilation system with heat recovy can reduce total energy consumption by 21.5 MWh per year. According to life cycle cost calculations the best system is heat pumps due to its small initial investment and good energy efficiency. The repayment period is less than 5 years. The payback period for a hybrid system is less than 8 years, for solar PVs just under 16 years. The most expensive is the ventilation system due to the large initial investment and relatively small energy savings, practically never pays for itself.