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I got a little bored and crunched out how much power my display consumes minus the controller. Then my dork mind jumped to the savings of LEDs and just how considerable it might be and I came up with this. Let's just say I knew the power savings were substantial but this shocked me.

Our theoretical intersection is a 4-way with two all-12" heads using 169 watt bulbs per thru approach and one 3M left turn signal per approach. There are also eight hand/man pedestrian signals using 69 watt bulbs.

8 normal signal bulbs 169W - 1352 watts
4 3M signal bulbs 150W - 600 watts
8 ped signal bulbs 69W each - 552 watts

Total Wattage: 2,504

Cost to run annually at 8.7¢ per KwH: $1,908.35

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Now let's say the county decides to upgrade the intersection. They ditch the 3Ms and throw in standard all-arrow left turn signals with LED arrows and everything else sticks around with LED upgrades. After all that, the intersection's power usage looks like this:

8 normal signal heads with Dialight LED modules: 67 watts - 8.3 watts per module, average
4 arrow left turn signal heads with Dialight LED modules: 24 watts - 6 watts per module, universal)
77.6 watts - 8 ped signals with Dialight countdown modules (9.7 watts per module, average)

Total Wattage: 168.6

Cost to run annually at 8.7¢ per KwH: $128.49

To put that into perspective, for the power required to run one 169W bulb, you could power an entire LED intersection, not including the controller.

I think our $/kwh is lower here but you're right about the savings. Each month I total all of the signal indications and our bill is based on the count of each. For example a 12" red lamp runs $2.19/month and a 12" red LED runs $.18 for a savings of $2.01 each month. Just ran the September report and we have 12608 indications at a cost of $2305.34 (was close to $10K before we started the LED conversion).

Why not just put LED bulbs in the 3M?

coyttl wrote::scratch: Why not just put LED bulbs in the 3M?

I was basing it off how things are done here and outside the City of Portland, nobody puts LEDs in 3M signals and a large majority of them are gone now.

3Mfanatic wrote:

coyttl wrote::scratch: Why not just put LED bulbs in the 3M?

I was basing it off how things are done here and outside the City of Portland, nobody puts LEDs in 3M signals and a large majority of them are gone now.

Oh wow, really? In MD, almost all 3Ms are LEDs now - as are the new McCain PVs going up. (Admittedly, some Yellow signals are sill incandescent..)

Washington County is fast-tracking theirs for removal along with all McCain PV signals and as of right now, only the City of Portland has plans to continue using 3M signals and they are all-LED. In fact, they actually bought a retired 5-section 3M from WaCo because they wanted another one! I know this because I called the county traffic engineer about a timing issue and happened to drive by the intersection and saw that it had been replaced so I asked him. We got a chuckle out of the fact nobody wants 3Ms up anymore and PBOT still can't get enough of them. Mind you this is the same City that never replaces anything and still has a few Eagleluxes floating around. ODOT seems to have it in for 3Ms, too but not quite the borderline fanatical removal schedule the county has implemented.

That's why I like LEDs even on old/classic signals; the savings in energy is a huge benefit and if it keeps the signal around longer, than everyone's happy .

All of this makes me wonder just how much major cities like NYC have saved by doing LED conversions...

weatherdan882002 wrote:All of this makes me wonder just how much major cities like NYC have saved by doing LED conversions...

Unless they notify Con Edison, The signals have NO METERS and are charged a monthly flat rate!!!

So someone has to do the math of wattage per signal for any savings......

We are flat rated so I tell Tacoma Power how many of each unit is out there. This includes the lamps that light the "ALL WAY" signs under the stop beacons. It's all handled by a little code that I wrote for my database and it automatically exports the data in spreadsheet format and emails it to TPU.

I not only maintain traffic signals, I write ACCESS application code to help me do it.

The benefits extend beyond power savings, too as we all know.

> Reduced emergency call-outs for red failure.
> Unlike an incandescent bulb, LEDs don't have a single point of failure like the filament of a bulb and tend to dim before they fail and though a complete and catastrophic LED failure can and does happen, I believe it to be extraordinarily rare. I think I've called in maybe two failed LEDs in the last two years or so and probably 95% of Washington County's first-round green Dialight balls (installed late 2001) are still going strong. They aren't as bright as they once were but they still get the job done.
> Possible safety benefit in brighter indication and the 'pop' of the instant on is more likely to get the attention of a distracted motorist.

weatherdan882002 wrote:All of this makes me wonder just how much major cities like NYC have saved by doing LED conversions...

Honestly I'd think cities like Los Angeles probably saw greater cost savings because a majority of the signals there are 12" and those require a higher-wattage bulb than an 8" indication. Correct me if I'm wrong, New Yorkers but aren't most NYC signals still 8"?