Extracting heat from a power supply can be dramatically enhanced by the right choice of materials and structure for its design. For example, providing efficient cooling via conduction through the baseplate is ideal for systems where active cooling through the use of fans is not desirable; such as professional-audio systems, which often need to be installed in areas where acoustic noise generated by electronic equipment cannot be tolerated. Elsewhere a suitably vented PSU case will allow the ready circulation of air for either natural or forced convection cooling. When considering the choice of power supply for a system design the use of higher efficiency units or supplies that will be operated below their full rated load can pay dividends. In the first instance, a 300W power supply operating at full load with an efficiency of 85% will dissipate 53W in heat, whereas a 90% efficient supply will waste 20W less in power converted to heat, potentially reducing or even eliminating the need for airflow-based cooling. In general, running a supply below full load will allow it to be operated at higher ambient temperatures where the rate at which heat can be removed from the vicinity of the power supply is reduced, or where the system requirements make it impossible to provide full forced-air cooling.