designed a process to obtain krypton from air. Production of krypton filled lamps based on his invention started at Ajka in 1937, in a factory co-designed by Polányi and Hungarian-born physicist Egon Orowan. By 1964, improvements in efficiency and production of incandescent lamps had reduced the cost of providing a given quantity of light by a factor of thirty, compared with the cost at introduction of Edison's lighting system. Consumption of incandescent light bulbs grew rapidly in the US. In 1885, an estimated 300,000 general lighting service lamps were sold, all with carbon filaments. When tungsten filaments were introduced, about 50 million lamp sockets existed in the US. In 1914, 88.5 million lamps were used, (only 15% with carbon filaments), and by 1945, annual sales of lamps were 795 million (more than 5 lamps per person per year). Efficacy and efficiency More than 95% of the power consumed by a typical incandescent light bulb is converted into heat rather than visible light. Other electrical light sources are more effective. For a given quantity of light, an incandescent light bulb consumes more power and emits more heat than a fluorescent lamp. In buildings where air conditioning is used, incandescent lamps' heat output increases load on the air conditioning system. While heat from lights will reduce the need to run a building's heating system, the latter can usually produce the same amount of heat at lower cost than incandescent lights. Compared to other incandescent (non-halogen) light types, incandescent halogen lamps will emit the same amount of light using less power, and a more constant output over time, with little dimming. Luminous efficacy of a light source is the ratio of the visible light to the total power input to the source, such as a lamp. Visible light is measured in lumens, a unit which is defined in part by the differing sensitivity of the human eye to different wavelengths of light (see luminosity function). Not all wavelengths are equally effective at stimulating the human eye. The units of luminous efficacy are lumens per watt (lm/W). By definition, the maximum efficacy is 683 lm/W for monochromatic green light. A white light source with all visible wavelengths present has a lower efficacy, around 250 lumens per watt. The luminous efficiency is defined as the ratio of the luminous efficacy to the theoretical maximum luminous efficacy of 683 lm/W for green light. The chart below