I am a big fan of LEDs, which have made great advances over the past 5 years. However, I have not been sold on replacing fluorescent tubes with LED tubes at a material cost of $50 per LED. The incremental benefit (a few more watts of savings) was not enough to overcome the incremental cost of the LEDs. For clients with low operating hours and/or low energy costs ($0.10/kWh), I have been playing it safe by retrofitting T-12 systems with T-8s or T-5s. The results are very predictable.
However, I was asked recently to try a $20 LED tube/strip with a different design. The “tube” has one flat side with two magnets. The magnets allow the tube to be snapped onto the inside of a ceiling-mounted fixture and wired directly to line voltage, reducing labor costs. LEDs also eliminate energy-wasting ballasts.
As an experiment for a client, I did a sample LED retrofit. Ultimately I chose the LEDs for the client’s project. Lighting levels and light quality were improved and energy cut by 65–70%.
I want to share this success story because it represents an opportunity for many buildings.
My client had 2-foot by 4-foot T-12 recessed fixtures with four lamps behind a lens. Because these lamps were phased out of production in 2014, the client had to make a change (see photo 1). My routine retrofit would replace the four lamps and two T-12 magnetic ballasts with two new T-8 or T-5 lamps and one ballast (see photo 2). I tested sample fixtures with T-8s in the client’s office. Then, out of curiosity, I also installed a fixture with the $20 LED strips next to the other test fixtures (photo 3).
This LED retrofit doesn’t require recycling of the old sockets, which may be near the end of their useful life anyway. You also don’t need to fit new lamp holders into your old metal fixture since the LED tubes don’t have the two pins at each end. The small magnets on the back of the LED attach easily to the back of the fixture. Installation labor was less because this retrofit had only five steps:
- Open lens
- Cut all the wires
- Remove the ballasts and lamps
- Snap in the two LED tubes
- Hardwire the tubes and close the lens.
That’s it! In the now vacant space where the T-12 ballasts were attached, I had ample room to contain the wire connections and wire nuts to satisfy our local electrical code.
Even though the operating hours were only 2,000 hours per year, the LEDs had a good payback:
Existing fixture energy Input: 144 watts/fixture
LED fixture energy input: 22w/tube or 44w/fixture
$15 installation per fixture
$11/fixture rebate from local utility (your rebate may be different)
Savings per fixture:
= (144 watts/fixture) – (44watts/fixture) * 2,000 hours per year
=200 kWh per year
@ $0.10/kWh, which equals about $20/year per fixture in energy savings.
When projecting your savings from these retrofits, you may want to include savings from reduced labor and HVAC load. But as you can see below, the payback is impressive without these factors:
Installation costs per fixture:
= ($20/tube)*(2 tubes) + ($15 installation) – ($11 rebate)
=$ 44 per fixture
=($ 44 per fixture) / ($20/ per year in savings)
Aesthetics, Risks and Downsides
Every office is different. Before moving forward on a full-scale retrofit, install some samples for a few weeks to see if the occupants like the new fixtures – or if they notice at all.
For this project, most surveyed occupants preferred reading under the LED fixture, probably because the color rendering index was higher (80 CRI) than that of the existing fluorescents (70 CRI).
Many LED strips/tubes come with either a frosted shield or clear plastic. Frosted is best if the strip/tube is visible to the occupants because it reduces the glare and the ability for someone to see the LED sources, which can be too bright for many people. The clear lens is useful for indirect lighting, when the light source is shielded from occupant view.
LEDs are basically tiny computers that are more sensitive to voltage or current fluctuations than fluorescent lamps. When testing, look for flicker when refrigerators, laser printers and other large devices turn on.
These LEDs had a 5-year, unconditional warranty. When they fail, my client will need to replace two $20 LED tubes instead of two $2 fluorescent lamps. However, if the retrofit economics are favorable today, they should be even more so in the future because LED manufacturing costs are falling rapidly.
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.