Saturday, April 21, 2012

Saving money with LED outdoor lighting

  • CFL bulbs contain mercury, not a very environmentally friendly choice



Project #1:  Outdoor (120V) porch light

Lesson one:  LED bulbs (and also CFLs) don't like dimmers.  That is one of the first things that I read about when looking for a light for my porch.  I did have a day / night sensor on my porch light, but I assumed it would be okay (I was wrong!).

For my porch light, I looked for a bulb that would be a direct replacement for the 15 Watt incandescent bulbs I had been using (and replacing frequently).  I wanted a bulb that had a "warm white" look to the light (not the usual bluish light typical of LEDs).  I found this bulb from Lights of America which was perfect for the job and only uses 2 1/2 Watts

Well, after about a week the light bulb burnt out - not a good sign.  Good thing I had a spare!  After a second bulb burnt out, I wasn't feeling so smart. I had a feeling my day / night sensor might be at fault.

I read a bit about day / night sensors and learned that there are different types.  I had one that is wired in-line with the light.  With only two wires, it doesn't ever completely shut off the power for the light.  In fact, I noticed that the LED bulb would still glow slightly during the day time (my first clue).  Even when fully on, the bulb would buzz audibly (my second clue).  I suppose incandescent bulbs can take the abuse caused by the sensor, but an LED bulb apparently can't.

Note that they do sell dimmer compatible LED bulbs, but they are more expensive (and might not even help in this case).  The problem was the sensor, not the bulb.  Here is a picture of my old sensor:

What I needed was a day / night sensor that fully switched off the light (e.g. with a mechanical relay).  I found these sensors by searching for "fluorescent compatible dusk/dawn sensor" (they weren't otherwise easy to find).  This sensor should work for any type of bulb (both CFL and LED alike).  Since it was cheap (and easy) enough, I simply replaced by old sensor.

Of course, I could have also simply disabled the old sensor.  LED bulbs use so little electricity, this would only be a minor waste and cost.  With the new sensor I'll save money mostly by making the bulbs (hopefully) last longer.

Besides, after destroying two bulbs, it was now a matter of pride that I make it work!

The new sensor was a direct physical replacement for my old one, I just needed to enlarge the sensor hole a bit and rewire the circuit per the included instructions.  Note the three wires below:

I even moved the sensor to a "smarter" position on top of the fixture so that the light doesn't cause it to switch off / on accidentally:

Here is my new LED porch light on with an (incandescent) outdoor column light in the foreground for comparison.  Note that the color of the porch light is a bit whiter, but still acceptable (in my opinion).

Project #2:  Low voltage (12VAC) landscape lighting

With the porch light done, I thought I'd tackle the (hopefully easier) outdoor lighting for my housing complex.

We have a 12V AC (low voltage) system with 18 lights in total.  10 of the lights are 25 Watt column lights and the remaining 8 are 16 Watt stake lights.   This is a total of 378 Watts!

Even with our timer / light sensor, they are on about 8 hours a day and consume about 3 Kilowatt hours per day (very wasteful in hindsight!).

In order to replace these lights, I found a low voltage LED bulb that:
  • Had a wedge base (compatible with our stake lights)
  • Worked on 12V AC (some bulbs are DC only)
  • Radiated light in all directions (just like the old bulbs)
  • Had a warm color temperature (like my porch light)
  • Long life (50,000 hours)
  • Low power (2 Watts)
  • Produced an equivalent amount of light (to the old bulbs)
  • Cheap enough to make replacing 18 bulbs economical

The above link is a reference.  I actually found the bulbs cheaper elsewhere at about $5 per bulb here.

After installing these bulbs the actual measured total power (using my handy Kill-O-Watt meter) dropped from 370 to under 40 Watts (a huge difference)!  I figure this is going to save $75 per year.  And, as a bonus, they are in fact brighter than the bulbs that they replaced!

As far as color is concerned, they are definitely "whiter", but since I got the "warm white" version, they aren't bluish - white like many outdoor LED lights.  They also now perfectly match my porch light.

Installation pictures

Note: For the outdoor lights, I had two types of fixtures to deal with (column lights and stake lights).  Both types of lights are low voltage (12 V AC).

Column lights

Note that our column lights are a bit unusual in that they use a regular (medium base) 120 Volt light fixture.  This was a pain because I had to find low voltage bulbs that screwed into a medium base (shown above).

While it is possible to also find low voltage LED bulbs with a medium base, they are more expensive and you don't have as many choices (like wattage and light color).  I thought it would be better if I could find an adapter which would enable me to use the same bulbs as I do for our stake lights.

In case anyone is interested, I bought the adapters (shown installed above with the LED bulb) from Harrington Lights (product id R3-MED-T5-WEDGE).

Stake lights

Note that the replacement LED bulbs are a bit taller than the incandescent bulbs that they replaced.  Fortunately, they still fit in the stake lights (but it was a much tighter fit as you can see below).


  1. This comment has been removed by a blog administrator.

  2. Sounds remarkably similar to my ongoing project to repair/replace garden lights with LED. I use G4 bulbs which look much the same as the wedge style you show, but the pins protrude which makes them really easy to wire into just about any fitting.

    I started doing it for reliability reasons, but when you can replace 20W lamps with 2W ones its starts to get you thinking about the financial savings too (I really like my garden lighting so it's on quite a lot).

  3. That sensor works really great. I also have that on our porch and garden lamps. Thanks for showing us this modifications.
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  4. Just like any other emergency vehicle lights, led outdoor lighting is also very helpful at home. It can be used to save energy that will surely lower your electric consumption, thus lowering your electric bill as well. In fact, I have the same kind of alternative lighting as well.

    Emergency light

  6. Your post gives new meaning to led light bulb decorations, I'll try your design schemes in my home's garden area.

  7. I think saving money
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  8. are your wedge LED lights weather proof? seems like the circuits on your garden stakes are exposed to the elements (in NJ where I leave I might get snow covering them). Was this a consideration?

  9. Yes, the wedge stake lights are exposed to the weather. Unless they are knocked over, rain should not get to the LEDs. I did check with the LED retailer and they claimed they were okay for outdoor use. So far, no failures or issues.

    We don't get snow here, so that could be a problem for these lights.

  10. CFL PROBLEM! IF you turn a CFL bulb on and off very often they fail quickly. Given the higher cost and environmental impact this is a bad choice. IF it is for an all night light then it is a good choice. LED light however are much cheaper and pay for themselves much quicker than CFLs. Look at your power bill and see the highest tier you are paying and then add taxes etc. This is the rate to calculate your savings from. It may be closer to 30 cent/kwh or more. Figure the hourly savings and hours and then figure you will not be replacing this light for probably 50,000 hours. LEDs pay for themselves very quickly over a halogen and then keep on saving. Once you do the math you won't believe you haven't done it sooner!

  11. I've considered replacing my outdoor lighting with LED bulbs, however, I believe it could damage the transformer to place a significantly lower load on it. Did you replace your 12-volt transformer when you went LED? If not, did you have any problems?



    1. Hi Ray,

      No problems, although my transformer has a low and high output setting. I switched to the low output since the reduced power draw was well under that rating (and, I assume, more efficient).

      I'd recommend checking to see if your transformer has a minimum output (or select-able output levels). If you were still below the minimum, you could obviously replace the transformer or consider only replacing some of the outdoor lights with LED to keep above the limit.

  12. What a great way to cut your electricity bill and at the same time making sure that the lights are always efficient, I be sure to try this out as well. Thanks!



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