Sunday, December 25, 2011

A Christmas LED Special

Do Christmas LEDs Pay for Themselves?

Our updated light display
now at my office
Each year LED Christmas lights become more widely available and better priced. But they're still on the expensive side. Old-style incandescent lights go for under $3 for a 100-light string, while LEDs start at about 4 times as much at $12 per 100.

Of course there are numerous reasons to buy LEDs:
  • in theory they should last forever
  • they can have color-changing and other novel features
  • you can string many 100s together on a single circuit
  • they are more durable and shock-resistant without filaments or glass 
  • they generate less heat, so less chance to start a fire (though MythBusters busted that myth)
  • it's just the right thing to do since they use so much less energy
But do they pay for themselves? More precisely, how long does it take, and how much electricity-cost do they save?

The old 50 lights burning 21.6 Watts
Case Study
We have some really old "Jesus" lights we put together right after we got married. We wanted a simple reminder of the kernel of Christmas in our apartment window, so I got some poster board and a string of 50 lights and spelled out the name Jesus, one letter in each pane of the balcony window. That string of lights is still working after 25 years(!)

But the lights are sure to burn out someday, and they consume 21.6 Watts of electricity. What about replacing them with LEDs? Even by doubling the lights to a 100-light LED string, the new string uses only 3.9 Watts of power.
New 100 LEDs burning 3.9 Watts

Note that the claims of 80% and 90% energy-savings on LED packaging are real, not just hype. 4 Watts of LEDs can replace 44 Watts of incandescents--that's just 9% of the power!

But what is the cost savings? Assume the lights burn for about 6 weeks (Thanksgiving through Three Kings Day, January 6) for 6 hours a day. Using my rule of thumb (that 1 Watt costs $1 per year), the cost of each string is:

50-light 22 Watt string:
21.6W x 42days/365 x 6hours/24 = $0.62

100-light 4 Watt string:
3.9W x 42days/365 x 6hours/24 = $0.11

So the new string saves 1/2 dollar a year. It will pay for itself in just 24 years! We can celebrate the savings at our 50th wedding anniversary. Well...the change has to be justified on principle and other ancillary grounds, such as, that 100 lights look better than the skimpy 50-light array.

Of course, if replacing 100 lights with 100 lights, the savings would more than double to $1.13 per year (= 0.62 x 2 - 0.11), so the payback period would be cut back to just 11 years.

Other Factors
Plus there are other factors that affect the payback calculation:

New strings
For a new string, the payback time is based on the cost difference between incandescent and LED strings. For a 100 light comparison, the price difference is $9, while the energy savings is about $1.13 per year, so the payback is about 8 years.

Discounts for recycling
Home Depot has an annual recycling program in early November each year at which they give away $3 to $5 coupons per string. This brings the payback time for replacement strings down to the same 8-year level as for new strings.

Reduction in future prices
Next year the price for LEDs is likely to continue to drop, further reducing the payback time. If a 100-light string drops to $9, the price difference will be $6, and the payback time will be 5.3 years. So plan ahead and keep an eye on the prices each year.

Rise in future energy costs
On the other hand, future energy prices are likely to rise, which also shortens the payback. By the end of the 24 year case study above, I expect energy prices to more than double. If they rise 6% a year, they'll quadruple! Based on 6% increases, a 24-year payback decreases to 14 years before accounting for inflation. If overall inflation runs at 3%, the term extends back out to 17 years. But that case study was skewed--because it doubled the number of lights.

On a light-for-light comparison with 6% increases in energy cost, the total replacement cost (without a coupon) is recovered in about 8 years, while the extra cost for a new string is recovered in about 6 years. (In each case, the 3% inflation adjustment is only +/-1/2 year.)

Bottom line
If you are going to buy new strings, definitely go for LEDs. Payback isn't immediate, but it's measurable. Know it's the right thing to do, and it will pay you back too.

If you are thinking of upgrading strings of lights, next year just might be the year! Plan ahead. Take advantage of coupons and discounts.

Christmas-Light Rules of Thumb
Just to have some ballpark numbers I can remember, let me summarize some rules of thumb.

100-light string Each Christmas
incandescents cost over $1
LEDs cost about 10¢
LEDs save about $1

So 20 incandescent strings show up measurably on your January bill by $20+, while 20 LED strings is imperceptible.

More Considerations
When choosing LED Christmas lights:
  1. Look for the Energy Star label. Energy Star compliant strings have been independently tested not only for energy use, but also for weatherization (if rated for outdoor use), longevity, protection against overvoltage, and they include a 3-year warranty.
  2. Look for "always on" technology--so the string stays lit even if one bulb is broken, burns out, or is removed. If a string doesn't advertise this feature, assume it doesn't have it.
  3. Stores do not stock many colors, but more colors are available online. Online suppliers also stock white wire and brown wire options along with green.
  4. Watch the whites: do you want blue-white, pure-white, or warm-white? Even among the same designation from the same maker, there may be variations, so be aware as you look.
Always Recycle!
Finally, don't just throw old strings into the dump. Even if you don't need the coupon, take your strings to Home Depot next year. Or search for other local or mail-in recycling alternatives. Here are some web alternatives I found that also claim to give discounts: Christmas Light SourceEnvironmental LED, HolidayLEDs.

Arise, shine, for your light has come,
   and the glory of the LORD shines over you.
For look, darkness covers the earth,
   and total darkness the peoples;
but the LORD will shine over you,
   and His glory will appear over you.
Nations will come to your light,
   and kings to the brightness of your radiance. 
(Isaiah 60.1-3)

Our new light display at home

Saturday, December 10, 2011

Sweater Weather and Long Johns

Fall is in the air, which--as my mother taught me--means it's sweater weather. Last week, President Lee Myung-bak of South Korea recommended wearing thermal underwear as an energy conservation measure in his country. Hearkens back to one of my earliest presidential memories--Jimmy Carter advocating energy conservation by putting on a sweater and turning down the thermostat.

Will Lee's long johns be a laughingstock in his country, just as Carter's sweater remains an object of ridicule for many people here? Only time can tell. Yet I remain baffled by the fact that most conservative politicians are not more 'conservative' when it comes to energy consumption. I'm disgusted when the likes of Ann Coulter and Rush Limbaugh ridicule energy conservation measures and pump the use of gas-guzzlers.

Sure I understand they are out to 'defend individual liberty' and 'property rights' and to fight 'tree worship', and I know they often speak tongue-in-cheek with lots of irony and satire. But while they may not literally mean everything they say, they certainly don't do enough to promote the enhancement of national security through energy independence. Sure they promote "drill here, drill now," but the most immediate way that American citizens can contribute to national energy independence is reduce! Conserve!

And we can have an immediate impact on our own personal finances and thus the national economy as well. The less money we send overseas for oil (to people who don't like us), the more we have to invest in our economy at home. And whenever we waste energy resources, we are not merely wasting our own pocket money right now: that which we waste we borrow from our children. We are creating an energy deficit for our heirs that is every bit as much of an albatross as the national debt we are hanging around their necks. For while the proven oil reserves keep growing, the actual oil reserves--what God has put in the ground for our collective use here on our planet--keep dwindling. They are finite, and there will come a time when they are truly scarce.

I can think of a couple of reasons Carter was mocked for wearing a sweater: on the one hand, it seemed unpresidential for him to stoop to talking details of sweaters and thermostats. It seems a bit like the president telling us to eat oatmeal for breakfast. Then too, it's just not concrete and easy to pin down just how much of a difference a little thermostat change really makes. In any event, Carter didn't adequately connect the dots between national security or other national interests and such small details as a change in thermostat setting. Yes we were going through hard economic times, but thermostat settings seem personal, like none-of-big-government's-business. It never became a patriotic cause--like victory gardens in WW2.

And maybe there's another reason--perhaps he asked too much 'sacrifice'--along with too small a justification. He called for setting daytime temps at 65° with a setback to 55° at night. Most people have a hard time with that, even with a boat load of sweaters and long johns. More recent suggestions have been along the lines of 68° for daytime (DOE) or 70° (EnergyStar). Last year, I was bent on setting our house thermostat at 68° (and I thought that was high) and my family wanted it at 72° (or above). Eventually we negotiated 69° as a compromise. And I agreed to let the kids use space heaters in their rooms. I tell my kids (with a wink) that God gave us sweaters for a purpose and they are learning to dress appropriately for the season.

I was proud of them at that point. Progress is a matter of degrees! It was something they grew into. Our bodies adjust, and often it's a matter of comparison. I've seen night guards in Nairobi shivering in 55° air wrapped in several layers of coats, while I was reveling in the beauty of a July night that was below 80°! They shiver because it's one of the coldest temperatures they ever have to deal with.

So how much difference can a few degrees make? Estimates come in wide ranges because because it depends greatly on the house, the weather, etc. DOE claims a 1° reduction for 8 hours a day can save 1% of heating costs (see their page for further discussion); equivalently, a 1° reduction 24 hours a day might save around 3%, speaking in ballpark terms.

But here's what it did for our house. This is a graph of our home gas usage for the past 7 years:
While there's an overall downward trend, it's a bit jumbled to read because of wide fluctuations in weather especially during January and February. Also, 2009 was a better year than 2010, adding to the spaghetti tangle. In all, however, the following table summarizes the gas usage for winter months versus summer months for 2011 versus prior years, with a resulting 20% reduction in heating consumption. However, when adjusted for the added electric consumption of the space heaters, the actual energy reduction was just 10%. Still, that's progress.

Average Gas Use (mcf/day)
Years* Winter*
Heating Load
(=Winter - Summer)
Heating Load
2005-2010 0.68 0.06 0.62
gas only
0.55 0.05 0.50 19.7% **
with space heaters***
0.62 0.05 0.57 9.9% ***
* The winter months are December through March and are listed by season according to the calendar year in which winter ends. For example, December 2010 is grouped with January through March 2011 to comprise the 2011 winter season.
** Based on thermostat set to 69°, down from low to mid-70's in prior years.
*** The mcf per day has been adjusted upwards to recognize increased electric usage due to space heaters. Adjustment made based on relative energy content using the conversion factor: 1 mcf = 302 kWh.

Bottom line: claims of 5% to 30% savings on heating costs based on modest thermostat adjustments are definitely within reach, both by turning the thermostat down all day and/or by using a setback at night or when no one's home. Here's a good article on the setback theory and practice, including a 3-year testimonial of a 28% reduction in heating costs, plus references to studies that consistently show significant savings are possible.

What about my office? I share once again a graph of my electric usage over the past 7 years. As can be seen by the dark green line at the bottom, this past January and February I managed to beat or tie both of the prior 2 years, which in turn greatly undercut the previous 4 years.
The following table isolates the average daily heating usage for winter months (December through February) by subtracting out the average April bill (minimal heating or cooling use):

Average Electric Use (kWh/day)
Years* Winter* April Heating Load
(=Winter - April)
Heating Load
2005-2008 68.6 48.7 19.9
2009-2010 39.0 31.0 8.0 60% **
2011 28.3 21.3 7.0 65% ***
* The winter months are December through February and are listed by season according to the calendar year in which winter ends. For example, December 2010 is grouped with January and February 2011 to comprise the 2011 winter season.
** Based on thermostat set in 50's (as cold as marginally-bearable with heavy clothing).
*** Based on thermostat set to 50° during the day and 45° at night, and using a personal 300W space heater.

Yes, this past winter I managed to cut my heating load by almost 2/3's! And that in spite of a bitter cold spell in February. Of course, I admit my thermostat settings were insanely cold at 50° daytimes and 45° nights. But that was for the overall building (house). Sitting at my desk was made almost-bearable by a little radiant space heater (300W). In reality the temp in my actual office was well north of 50°, maybe close to 60°. And yes, I wear long johns and sweaters both!

So does it matter that someone else has their thermostat cranked up to 80°? That is, does it matter to you and me, to society? In truth it does. Not just in the big picture, long-term impact. But it hits one's neighbors right now. Remember those rolling blackouts here in Texas last February during that bitter cold snap? And everyone's electric cost is impacted sooner or later by the maxing-out of the power grid. I'm sure there were people last February who thought they had a right to a toasty home or office. Maybe they think they've earned the right as an American citizen.

They forget it is supremely a gift from God that they were born in this land of opportunity and can earn a living and provide for their family here. Every blessing from God is given so we in turn can be a blessing to others. Let's see now, am I my brother's keeper? Or let me ask, who is my neighbor?? It is disgusting that some conservatives choose to mock the wise actions of responsible people, and to scoff at voices that advocate reason in the matter of stewarding God's resources.

The LORD mocks those who mock,
but gives grace to the humble(Proverbs 3.34)