Heating, ventilation, and air conditioning (HVAC) equipment accounts for 40% to 50% of a commercial building’s energy usage. This energy is supplied using either electricity or natural gas. Combustion products from natural gas pollute the environment and the burning of fossil fuels to produce electricity also pollutes the environment. The world must turn to clean, renewable energy resources to stop pollution. Solar energy has the potential to play a huge role in the renewable energy movement. Solar energy can be harnessed through active or passive solar techniques. Active solar uses solar collectors to harness the sun’s energy and passive solar uses heat transfer through architectural features to transfer the sun’s energy as heat. The exterior walls of commercial buildings are typically bare, plain walls. Why not use this space to harness solar energy for space heating? This report will analyze two identical commercial buildings, one in St. Louis, MO and one in Phoenix, AZ. Both buildings will have flat plate solar collectors installed on the south facing wall and the peaking heating demand will be compared to the amount of solar energy that can be harnessed at that time. The peak heating demands are calculated using Trace 700. It was found that on January 17th at 1:00 pm, the St. Louis system could harness 104.2kW of solar energy (33.2% of the heating demand) and the Phoenix system could harness 465.8 kW of energy (290.8% of the heating demand.) This proves that solar energy has the potential to play a huge role in the world of renewable energy, but the size of its impact is dependent upon location