For a growing number of users, especially those who are environmentally conscious, photovoltaic technology is a clean option. Photovoltaics provide sustainable energy, quiet operation, no toxic gas and greenhouse gas emissions, and no hazardous waste. Photovoltaic systems generate electricity from free solar energy, so operating costs are virtually non-existent. Moreover, continued research and development means that the installation costs of photovoltaic systems will gradually decrease. Some would prefer to invest capital in improving the way energy is produced, rather than continually giving money to power companies. Others like to reduce the amount of electricity they buy from the grid because it reduces their exposure to power cuts and future price increases.