Design Volts: The voltage for which the lamp was originally designed. All other ratings (amperes, brightness, and life) are measured at this voltage, and can be changed by rerating the voltage.

Design Amperes: The approximate current the lamp will draw at design voltage (stated amperage ratings are plus or minus 10 percent). Wattage can be calculated by multiplying design volts by design amperage.

Design Life: The rated average laboratory life when lamps are operated under stable environmental and electrical conditions. Actual life will vary with the particular application.

Where lamp replacement is difficult, light output can be sacrificed for longer life. A reduction in the applied voltage (see lamp rerating below) will also increase lamp life significantly. Lamp life varies inversely to the 12th power of the ratio of the applied voltage versus the design voltage.