About a year ago, I wrote about “snap-in” LED retrofits. One of the key advantages of this design is that it is ballast-free, which removes an energy consumer and a potential point of failure. The LED tubes look a little like lightsabers from the Star Wars movies because they do not have pins on their ends, unlike fluorescent lamps and other LED tubes. They also do not need any lamp holders (aka tombstones), which removes another point of failure and a potential hassle because old plastic lamp holders often break during installation of new lamps.
The LED tubes are wired directly to line voltage and snap into the existing fixture with magnets. Many clients have reported high CRI lighting and good energy savings.
Today, I present a case study on applying this design approach to a high-bay application. Specifically, I will show the cost advantages of removing T5HO lamps or T8 lamps and replacing them with LED tubes on a one-to-one basis. Replacing a relatively new T5 system with LEDs may seem baffling, but when you’re going from 230 watts per fixture to 96 watts – while doubling lamp life and maintaining brightness – it makes sense to investigate.
If you are unfamiliar with T-bay fixtures, you can see this type of high-bay lighting in many Sam’s Clubs, Wal-Marts and Costco warehouses.
The building in this application had T-bay fixtures mounted over 20 feet high, each with four 54-watt T5HO lamps per fixture. The lamps and ballast were consuming about 230 watts per fixture while providing adequate lighting. The retrofit involved removing all four lamps and the ballast, which results in an empty fixture with only the incoming power wires remaining and the empty lamp holders.
The line voltage wires were connected directly to the first LED tube. Connector whip plugs allow the remaining LED tubes to be quickly wired in series. Each tube has magnets on one side, so they just snap in. Within minutes you can have four LED tubes mounted where the fluorescent tubes were located. Figure 1 below shows how the LED tubes are connected.
Figure 1. LED Tube Connections
You can also use this installation design to replace 8-foot fluorescent lamps by using a connector whip between two 4-foot LEDs end to end. In that case, you are going from a minimum of 200 watts (two F96T12 lamps) to only two 4-foot LED strips end to end, which give off enough light and only require 48 watts and no ballast losses.
Cost Breakdown for the T-Bay Retrofit
Existing fixture energy input: 230 watts/fixture
LED fixture energy input: 24w/tube or 96w/fixture
Material cost: $40/tube
Electrical demand cost: $7/kW per month
kWh cost: $0.10/kWh
3000 operating hours per year
kW savings per fixture:
= [(0.230 kW/fixture) – (0.096 kW/fixture)] * [$7/kW * 12 months/year]
= $11.2 per year in Demand (kW) Savings
kWh savings per fixture:
= [(0.230 kW/fixture) – (0.096 kW/fixture)] * [$0.10/kWh * 3,000 hours/year]
= $40.2 per year in kWh Savings
The total dollar savings per fixture would be about $50 per year. However, with such retrofits, you may also want to count the savings on labor and material for relamping as well as HVAC savings.
Installation Costs per fixture:
= ($40/tube x 4 tubes) + ($25 installation)
= $185 per fixture
= ($185 per fixture) / ($50/ per year in savings)
= 3.7 years
In addition, there may be current tax and utility rebates that can help you reduce your payback by 50% and more. These were addressed in previous column articles and there are also webinars about them online.
Aesthetic Benefits, Risks and Downsides
Whenever you do a retrofit, install some samples for a few weeks to see how the occupants like the new fixtures (or if they notice at all). You want to be sure the LED lights aren’t contributing to glare, although this is not usually an issue in high-bay environments.
Many LED strips/tubes come with either a frosted shield or clear plastic. You should test which is best for a particular environment before doing a whole building retrofit. In many cases, the LEDs will provide a brighter environment with more vibrant colors. Some building managers have chosen to retrofit a six-lamp fluorescent T-Bay with only five LED tubes, which can maintain the light levels while achieving additional savings.
As I have experienced on other LED installations, LEDs are basically minicomputers that can be sensitive to voltage or current fluctuations. Regarding maintenance, when the LEDs eventually fail, you’ll be replacing $40 tubes which requires a larger budget than fluorescent lamps. However, if the retrofit economics work today, it’s likely to work in the future too. In addition, material costs of LEDs are likely to be much less five years from now. Even though these LEDs have a five-year unconditional warranty, it is likely they will last about twice as long as the fluorescent systems. The ballast-free LEDs also have fewer points of failure to worry about. You can learn more about ballast-free LED retrofits by checking out this video which explains the basics of installations and project economics.
I am excited about the simplicity that this LED technology provides. It provides good energy savings and short paybacks, as well as improved lighting conditions. I don’t typically mention brand names in an article, but if you want to learn about these snap-in LED tubes, feel free to email me (firstname.lastname@example.org) and I will provide the name of the manufacturer.
Eric A. Woodroof, Ph.D., is the Chairman of the Board for the Certified Carbon Reduction Manager (CRM) program and he has been a board member of the Certified Energy Manager (CEM) Program since 1999. His clients include government agencies, airports, utilities, cities, universities and foreign governments. Private clients include IBM, Pepsi, GM, Verizon, Hertz, Visteon, JP Morgan-Chase, and Lockheed Martin. In August 2014, he was named to the Association of Energy Engineers (AEE) Energy Managers Hall of Fame.