One of my favorite aspects of our annual Christmas display is going outside when the crowds start to gather because I really enjoy catching the expressions on spectator’s faces. Most often people see me exit the house and start talking to me once I get to my “candy cane distribution point” across the street.
The most popular question is “Wow, what’s your electricity bill like?” I should probably add an exclamation point based on how it’s often asked, but Mrs. Peck (my 5th grade English teacher) might object to that punctuation. My response is always “Actually, my bill has gone down for the month of December since I started doing the animation” and everyone becomes perplexed. I suppose it is counter-intuitive for novices. More lights should require more power, right? Then I add, “Most everything I’ve added is LED-based and two years ago I started replacing the older lights with LEDs.” People almost seem comforted by the information. Go figure. I suppose it’s easier to grasp LEDs typically use less power than the same number of similarly-sized incandescent lights. Now that LED lighting has become more mainstream the advertising is getting the message across.
Disclaimer: The assumptions, calculations and conclusions provided within this article are for illustration only and are not meant to represent any particular make, model, brand, or part number. The author assumes no liability for these numbers and urges all readers to seek the assistance of qualified local electrical expertise before utilizing the information provided in a practical implementation.
However, as I read through the PlanetChristmas forums I notice many conversations related to the use of LEDs as a way to conserve power and reduce the electric bill. The various threads are always similar and almost always seem to stir up some heated debate between the participants. Much of the discussion attempts to resolve the conflict over whether or not the use of LEDs for a holiday display actually lowers the electric bill or not. I think the whole topic is a little misguided, if not completely irrelevant.
Static displays (those that do not implement animation) do indeed consume significantly less electricity when using LEDs than traditional incandescent lights. But realistically, if we’re talking about a situation where the lights are on about five hours per day for about thirty days, is it really that big of a deal? Let’s do some math and decide.
Assume a display consumes about 200 amps of power (this would likely represent a pretty big static display) for 150 hours (5 hours x 30 days) each year. The display constantly consumes 24,000 watts of power while operational. That means the display is consumes about 3,600,000 watt-hours, or 3,600 kilowatt-hours as the electric company likes to bill you. How did we get those numbers?
A kilowatt-hour (kWh) is 1,000 watts of continuous consumption for one hour. If you are consuming 200 amps continuously for 5 hours each day, that would be 1,000 amp-hours per day. Since wattage is amps times volts, 1,000 amp-hours times 120 volts (using the United States as a reference) is 120,000 watt-hours per day, or 120 kWh. Multiply this daily number for the 30 days the display is lit and you get 3,600 kWh. Depending on where you live, your electric rates range between $0.05 and $0.22 per kWh, which means the electricity cost of operating the display is between $180 and $792. An average is $330.
If we can believe the published power consumption numbers from the vendors where LEDs boast electricity savings of 80%, the annual cost to operate the display would drop from $330 to $66. While that may seem like a dramatic reduction, the reality is the cost of the LEDs needed to realize those savings could go well into the thousands of dollars. For a Christmas display, today’s LED’s power consumption savings don’t even come close to offsetting the electrical costs when a string of 100 M6 LED lights is $25 and a string of 100 incandescent minis is $2.50. Based on today’s LED technology it’s not likely that the lights, or more importantly the wire they are attached to, will operate long enough to realize a break-even point. Ten years, even if handled and stored properly, may be a little too much to ask to just break even, especially when we can assume the technology will continue to improve and the price points will eventually decrease.
Not to throw salt on the wound, the cost savings for animated displays is almost negligible, certainly far lower than the amount realized with static displays. If you consider in typical animated displays, particularly those that are synchronized to music, most of the lights are off longer than they are on. If we assume animating a static display results in all the lights being off at least 75% of the time, then the $330 worth of electricity for the incandescent lights just became $83 or less in electricity costs. For reference, if you were using LEDs the display’s costs would have dropped from the previously-calculated $66 to about $17. Again, the difference between $83 and $17 probably isn’t as significant as the cost of the LEDs to get there.
So there’s the proof. LEDs don’t really save you anything for a Christmas display.
OK, maybe it’s not that simple. After all, there are lots of claims of power reduction and cost savings with LEDs, so why isn’t this holding true here?
To be fair, the claims are mostly true, but the information needs to be put into proper context. If you were using those lights every day of the year for five hours the electrical consumption cost difference ($3,960 versus $996) begins to justify the LED’s higher acquisition costs. In situations such as office buildings where lights are typically on for 10 hours per day, the differences between traditional lighting and LEDs ($7,920 versus $1,992) are more difficult to ignore. Finally, a 24 hour store would compare at $19,000 versus $4,780. Remember, these are monthly numbers. Now the justification of replacing even fluorescent fixtures, which were previously considered very cost-efficient, with LED-based ones starts to make sense.
So the LED electrical consumption cost savings argument – at least for Christmas displays – may be a bit irrelevant, at least in terms of the holiday display’s eventual electrical bill. But there are other very real cost considerations display enthusiasts should consider when contemplating the move to LEDs. The differences in infrastructure costs are significant, starting with power distribution.
Let’s assume you have a single 15 amp electrical outlet available for a static display. If you stick to the “80% rule” for safety, that means there are 12 amps available for constant use in the display. What could you do with 12 amps? Table 1 provides some examples of what would drive this standard 15 amp circuit to capacity. Each row stands on its own, meaning that any one row would use the entire circuit.
15 amp Circuit Capacity
Bulb / String Type Power Draw Max Qty Total Bulbs
100ct Mini 0.33A / 40W 37 strings 3,700
25ct C7 1.04A / 125W 11 strings 275
25ct C9 2.08A / 250W 5 strings 125
50ct LED 0.02A / 2.4W 600 strings 30,000
25ct C9 LED 0.2A / 25W 57 strings 1,425
As you can see the difference between incandescent and LED bulbs for the same circuit is very significant. What if we compared at typical 20 amp circuit the same way? Take a look at Table 2.
20 amp Circuit Capacity
Bulb / String Type Power Draw Max Qty Total Bulbs
100ct Mini 0.33A / 40W 48 strings 4,800
25ct C7 1.04A / 125W 15 strings 375
25ct C9 2.08A / 250W 7 strings 175
50ct LED 0.02A / 2.4W 800 strings 40,000
25ct C9 LED 0.2A / 25W 76 strings 1,920
The bottom line is a single 20 amp circuit could handle about 40,000 LED minis or almost 2,000 LED C9 bulbs. It would take eleven 20 amp circuits to carry as many incandescent C9 equivalents. This is where the true infrastructure costs come into play.
Finding eleven unused electrical circuits in a typical home is tough. Tougher is finding eleven vacant slots in a breaker panel. So even once you get past the cost of subpanels for more circuit breakers you still have distribution costs. That means extension cords. Lots of extension cords. Using the numbers above, assuming you could find eleven 20 amp outlets to use, eleven 50 foot 12 AWG outdoor extension cords cost about $440, and eleven 100 foot 12 AWG outdoor extension cords cost about $616. Plus, they’re heavy, tedious to set up and take down. Again, this assumes available circuits and outlets. If additional subpanels are needed the costs go up significantly for the panels themselves, wire, outlets, electricians, etc.
In many cases a subpanel may not be feasible due to the existing utilization of available power. Many homes, particularly those that have electrical appliances like stoves, ovens, clothes dryers, and hot water heaters, already utilize a high percentage of the maximum power available.
In my own case, before considering LEDs, if my 2007 display used only incandescent lights, they would have consumed over 250 amps of power during certain peaks in the performance and it wasn’t feasible. In 2007 all the lights on the face and roof of the house were LEDs, and this helped keep the power consumption peak at about 165 amps, which is right at the edge of what I could safely handle and keep the required power reserves. Since then more and more elements have been replaced with LEDs (60 strings in the two oak trees in the front yard alone) and the power consumption continued to decrease. In this case using LEDs did not necessarily mean the display cost less to operate but because the infrastructure costs and the overall electrical needs of the main panel were reduced, LEDs were appropriate.
In 2008 I added several items to the display, including two 20 foot 180-degree mega-trees, one on each side of the house. Each one of those trees has 96 strings of LEDs comprised of 24 strings and each of four colors. The total power consumption for each tree, assuming all 96 strings are on at 100% at the same time is 240 watts, or two amps per tree. If the tree had been strung with conventional minis those 96 strings would have consumed 3,840 watts, or 32 amps. By using LEDs, the six light controllers used by each tree to drive the lights could easily be fed with a single 18 AWG SPT-2 extension cord whereas traditional incandescent minis would have required two dedicated 20 amp circuits and two expensive 12 AWG extension cords per tree.
Given the comparison of extension cord costs alone made this a simple decision. Another major consideration was serviceability. It was likely some of the incandescent mini-lights would fail during the season. Servicing them while on the 20 foot tree would be tedious at best. It was very unlikely that any service would be needed on the LED strands.
Using an example that perhaps everyone reading has seen before, let’s look at the house used in the movie “Deck the Halls”. The scenes where the home was fully animated to music used 14,300 Color Kinetics RGB LED nodes. These nodes could be programmed to generate just about any visible color. At full intensity, the LED nodes consumed about 7,150 watts of power or about 60 amps. If that house would have been wrapped with traditional incandescent C9 string lights the power draw would have been over 100,000 watts, or about 834 amps. I don’t know of too many residential locations with that kind of available power. In addition, the C9 lights would not have provided any of the animation control or color-changing capabilities like the RGB LED nodes did.
This season my display will be replacing 32 four-color mini trees with LED-based ones. This will represent an overall power consumption reduction of about 4,800 watts. This is good news, especially given the planned expansion this year to a total of 96 LED-based four-color mini trees. The mere 950 watts consumed by all 96 four-color LED mini trees pales in comparison to the almost 5,100 watts consumed by only the original 32 four-color mini trees.
So, in the end, while power consumption is still perhaps one of several major forces in selecting LEDs over incandescent bulbs, it isn’t to reduce the electric bill. It is a much more a matter of lowering the overall infrastructure and distribution costs, increasing bulb quantity and decreasing servicing needs.
About the author: Fabian Gordon has a long history as a professional musician and audio production engineer, and has been a strategic and architectural computer software and services design consultant for almost 30 years. Christmas lighting is something he was fascinated with since a very early age, and he has been at the forefront of the transition to quality LED lighting. His efforts in this area have earned him the nickname of the “LED KILLER” by fellow Christmas enthusiasts.
From the August 2009 edition of PlanetChristmas Magazine
by Fabian Gordon