The investment costs of high-pressure sodium-vapour lamps are generally two to four times lower than those of LED systems. However, the return on investment of LED-based lighting can be achieved after just one to two years, as their energy consumption is so much lower. This is called wall-plug efficiency; the ratio between optical power and electrical power, or what percentage of power is converted into light.
The most efficient high-pressure sodium system available can achieve a wall-plug efficiency of more than 50%. The most efficient LED system with a combination of Hyper-Red 616-nanometre LEDs and Deep-Blue 450-nanometre LEDs (these two wavelengths are perfect for horticulture applications) can reach values above 80%.
At the right temperatures (below the maximum operating temperature), LEDs work for up to 60,000 hours, which equates to 9.1, 13.7 and 20.5 years if they are operated for 18, 12 and 8 hours per day respectively. At higher temperatures or when running on higher currents, this figure drops significantly. LEDs can be operated at up to around 70% of their light output.
High-pressure sodium-vapour lamps (1000W) equipped on both sides have a service life of 10,000 to 24,000 hours, i.e. 3.7, 5.5 and 8.2 years with an average use of 18, 12 and 8 hours per day. However, because operators want to comply with the required lumen values, you can expect to have to replace the bulb within the first five years.
Metal-halide lamps have a lifespan of between 6,000 and 20,000 hours, while fluorescent bulbs (T-5 and T-8) have a lifespan of 20,000 to 36,000 hours. Again, due to compliance with certain lumen values, lamps are expected to be replaced before this maximum is achieved.