Deciding what type of lighting to use in the greenhouse is an important and complicated matter for growers to address. Not all lighting works for every grower and, sometimes, the cost to upgrade can be too expensive.
Bruce Bugbee, a professor in Utah State University’s Plants, Soils and Climate Department, has been working on this question with growers in recent months. In his opinion, growers should still consider upgrading to newer high pressure sodium (HPS) lights. Specifically, the initial investment in HPS lights is less than LEDs, and the technology is still being improved.
“LEDs cost close to 10 times as much per photon output,” says Bugbee, who notes that LEDs can still be cost effective in the right environment, says. “So, for an equal amount of light, your initial investment is much, much higher with LEDs. It’s analogous to people putting solar panels on their house where the solar panels pay for themselves, but the payback period is 10 to 20 years.” For HPS lights, payback can take as little as two years.
When it comes to technology, Bugbee says it is the combination of two advancements that make HPS lights a worthwhile option. First, double-sided HPS bulbs were introduced to the market around five years ago. Around the same time, electronic ballasts were also introduced. According to Bugbee, the two technologies combined are 40 to 50 percent more efficient than older, mogul-base lights.
So, when growers are comparing lights and perhaps deciding between LED and HPS bulbs, it’s important to make the comparison using the right HPS bulbs.
“There’s a lot of LED people that say [LEDs] are better than the old mogul-base sodium lights,” Bugbee says. “But that’s not the state of HPS lighting. They need to compare [LEDs] to 1,000 watt, double sided, high pressure sodium bulbs.” Bugbee says lamp life being double from what it used to be also gives HPS lights an advantage.
He also notes that upgrading HPS lights is often less expensive that installing an entire new system for LEDs. As mogul-base lights are being phased out because, as Bugbee puts it, the technology is “obsolete” and growers may be forced into choosing new lights. Because of the higher initial cost of LEDs, growers looking to improve their operation while keeping costs in check may want to look at HPS lights. In addition to cost, Bugbee says return can happen that quickly if growers properly clean and maintain their lights. New HPS technology is 40 percent more efficient and the old mogul options could simply be keeping growers from reaching maximum efficiency because the bulbs are simply worn out and dirty from many years of use.