[Update: See the bottom of the post for a quick update thanks to some issues pointed out by Nicolas Marmet in the comments.]
[Update 2 (1/26/2014): I added graphs for the cost per hour instead of the cost per day assuming 3 hours of use per day. I s'pose it would've made sense to just start with these graphs. Oh well.]
In the 1960s Walter Mischel performed studies involving preschoolers and marshmallows. The "Marshmallow Experiment" involved sitting kids in a bare room and setting a marshmallow1 in front of them, then telling the preschoolers they could either eat the marshmallow now or wait 15 minutes. If they successfully waited 15 minutes then they'd get a second marshmallow to enjoy in addition to the first.
In addition to telling us something about deferred gratification, it's also immensely fun to watch preschoolers in agony attempting to defer their gratification:
http://www.youtube.com/watch?v=6EjJsPylEOY
This past week I needed to pick up two new lightbulbs for our oven hood. I noticed our local big box home supply store had a fancy new LED bulb that would fit into the outlet. On the downside the LED cost $32.98 compared to $7.98 for the same type of halogen bulb that just blew out. Wow. $32.98 feels really expensive for a lightbulb. I decided to get one of each then do a little cost analysis when I got home.
Here are the vitals for each bulb (according the packaging):
Halogen Bulb | LED Bulb | |
---|---|---|
Power | 50 Watts | 7 Watts |
Lifetime | 2,500 hours | 25,000 hours |
Let me assure you our old halogen bulbs didn't last nearly as long as 2,500 hours. I'd roughly estimate those bulbs are on an average of 3 hours a day. The halogen bulbs should have lasted about 2.25 years at that usage. This is the second time I've had to replace these bulbs and we've only been in our house 3 years. Does this mean the LED bulb will have a shortened lifespan as well? I don't know. I'll cut the bulb makers some slack this post and assume their numbers for the lifetime of the bulbs is accurate.
How long before the LED pays for itself?
The LED bulb uses about one-seventh less power and has 10 times the lifespan of the halogen bulb. It seems pretty clear that at some point it'll eventually pay for itself. But how long will that be? Days? Years? Decades?
I hunted down a bill from the electric company and added up all the government surcharges, distribution rates, and so on. Hmm...it seems like they should print the total rate you actually pay instead of only listing the seven different surcharges individually. It'd certainly make it quicker to see what you're paying. Anyway, I pay $0.15373 per kilowatt-hour. What does that mean? It means that if I leave a 1000 watt lightbulb on for 1 hour, it'd cost me $0.15373. Knowing that, I can figure out how much it costs me to keep the LED and Halogen lights on for 1 hour:
That's nice to know, but the time has come to make a chart:
You might be wondering why the data points jump every so often on the graph. Let me explain: The halogen bulb line jumps $7.98 after every 2,500 hours of use. Why? That's the bulb burning out and me running out to the store buying a new bulb for $7.98. You'll notice the LED cost jumps $32.98 after 25,000 hours of use. Same deal.
I added in best-fit2 lines and had Excel whip up the equations for those lines. The trendlines' slope is the cost per day (assuming the bulbs are on 3 hours a day). I'm really interested in the intersection of the two trendlines. It's at that point where the LED bulb is actually saving me money. We can see they cross just before 1000 days. We can do better than that. If I subtract the two equations from each other, I should get an equation that gives the difference in cost between the two bulbs:
What does this tell us? Well, it says the difference in cost between the two bulbs in $25.00, and for each day of use (x), the LED is $0.0277 cheaper to operate than the halogen bulb. So how many days until the difference in cost between the LED an halogen is $0.00?
or
2 years, 5 months, and 20 days
.
Deferred gratification
LEDs save money. They're more efficient. They last longer. But...paying $32.98 for one lightbulb and then waiting nearly two and a half years before it pays itself off can be nearly as painful as a 4 year old waiting 15 minutes for a second marshmallow. In both situations the end result is desirable- but it involves subduing that part of your brain that says, "Mmmm...marshmallow...so tasty...must. eat. it. now." or "HOLY #$*&@! $33.00 for ONE lightbulb!" You just have to keep telling yourself that second marshmallow's on its way and that after 25,000 hours that LED bulb will have saved you over $200.
A related student activity
It seems that many sustainable technologies (LED bulbs, electric cars, photovoltaic cells) require more money up front. Over time, just like the LED bulb, they generally pay for themselves. Have students investigate whether these extra costs pan out by having them pick a sustainable technology (like buying an electric car) and by doing some research into, for example, their family's driving habits. After a few calculations they can determine how long it would take for the electric car to pay for itself compared to an equivalent gas-powered car. Open up the topic to students- let them pick topics that interest them. Have them do additional research into the costs and benefits beyond just dollars and cents. Encourage them to interview people who have already implemented these changes. Most of all, let them take the time to puzzle over how to figure this stuff out. Be there to help and guide them, but please, please, don't just give them worksheet that has them plug in some numbers to get some type of answer.
UPDATE
Nicolas Marmet (in the comments) pointed out a few things that I think are worth addressing, primarily the issue with not continuing the data in the chart above for several lifetimes of the LED bulb. I didn't think there would be much effect, but just because I was curious, I made a new chart (below) that goes through 11 lifetimes of the LED bulb:
As you can see, the slope of the best-fit line jumps from 0.0042 dollars/day to 0.0070 dollars/day. While that's still significantly cheaper than the Halogen bulb (at 0.0319 dollars/day), it's different enough that some new calculations are in order. After updating the Savings equation (from above), the new equation looks like this:
$latex \text{Savings}=\$ 25.00 - 0.0249x&s=3$
This tells us that it'll take an additional 102 days than the calculation above until the LED is the cheaper choice. It'll take 1004 days, or 2 years and 9 months until the break even point. Not too much longer, but still longer.
Also, a quick run through Nicolas Marmet's other points:
- As far as the difference in lumens between the two bulbs, I no longer have the boxes pictured above, and can't make out any lumens listed on the boxes in the picture above. Qualitatively looking at the lights side-by-side in my house, I don't notice much difference in brightness between the two, and I'd pick the LED as the brighter bulb- though perhaps that's a trick due to the whiter quality of its light.
- I can't say much about the premature failure of LED-bulbs other than to point out that my LED bulb hasn't failed yet- though as of this update it's only been 327 days since being installed, which assuming 3 hours per day of use, is only 3.9% of the bulb's 25,000 hour lifespan, and I'm still 2 years, 10 months, and 8 days away from the break-even point. I'll update this post again once either bulb has failed.
- LED buzzing: The LED I installed doesn't buzz at all. It has made no noises at all that I've been able to perceive. My cats don't act weird (or I guess I should say, weirder than normal) when it's on, so that's not an issue.
While there's certainly a lot of time left where I could be proven wrong, it does still seem over the long-term the LED bulb is a smarter investment, though you're probably not going to be able to retire early from the savings gained from using LEDs.
UPDATE 2 (1/26/2014)
Here are two views of the same graphs using Cost per Hour instead of Cost per Day of 3/hr use:
Below I zoomed in to only include the costs up to 3200 hours so the break even point becomes more clear.
So, after 2906.98 hours of continuous use (or 121 days), it becomes cheaper to purchase a 7W LED bulb over a 50W Halogen.
- According to the Wikipedia, Mischel let kids choose whether they wanted a marshmallow, Oreo cookie, or pretzel stick. I guess the "Marshmallow, Oreo, or Pretzel Experiment" doesn't quite roll of the tongue as nicely. [↩]
- I set the y-intercept for the halogen and LED bulbs at 7.98 and 32.98, respectively. Since you're paying that money up front, it follows that at time zero (when you've purchased the bulbs but haven't used them yet) you're already out the cost of the bulb. [↩]
Love it! Great idea. I'm going to adapt this to an activity for my environmental science class. I'll make it available at http://www.thelessonlocker.com. Thanks!
We recently remodeled a bathroom. Our light fixture it a four bulb fixture. Within about 2 hours my wife was commenting on how she could feed the heat coming off of the four bulbs... so I went to the local Home Depot and picked up some LED bulbs. She's much happier and I agree the LED bulbs run a lot cooler. I don't know how much of an effect they had on the room temperature, but at about 4 feet it was noticeable, so I'm sure there is also the cost of additional cooling required to cool down that room. Relatively negligible I'm sure, but it is an additional cost I'd never considered until I experienced the heat in a real way under "normal use".
There are a few problems with what you describe here.
-There is a small inaccuracy in the graph. The idea of using several life times for the bulb is to amortize the initial cost. The line for LED is done on the first and a fraction of the second LED. The slope of the line would be bigger if done properly.
-The energy smart 7W LED generates only 300 Lumens compare to the 50W Halogen bulb that generate 900 Lumens. It would have been more accurate to compare the LED with a 20W bulb.
-There is a lot of premature failure to the LED and the impact is a lot bigger than halogen bulb.
-At the end not much saving there and you have to live with all the buzzing and other problems that come with the LED.
I did wait 15 minutes for the second Marshmallow but I should had eaten the first one while it was still fresh.
A bird in the hand is worth two in the bush.
@Nicolas: You bring up some interesting points, especially about the inaccuracy of the graph due to including too few lifetimes of the LED bulb. I updated the post and included 11 lifetimes of the LED bulb and redid the calculations based on the new best-fit line. It did increase the effective cost of the LED bulb, but not by all that much. I also responded to a few of your other points in the updated post. Thanks for pointing this out!
Ben,
Human eye is capable of responding to an enormous range of light intensity. The eye response to the light intensity is not linear and it does not help to make accurate side by side comparison. I suspect the lamp that you have is the 7-Watt GE energy smart that you find on the web site: http://pressroom.gelighting.com/news/7watt_led_par20#.UbCiMr2RJIp
From that web site it you can find the 7-watt lamp will generate (200 lumens). I was surprise to find on that same page only 570 lumens for a 50 watt halogen. I have seen on a lot of web pages between 800 and 950 lumens for halogen. Halogen is like LED for the same number of watt some are better than others. At the end you will need 3 x 7-watt lamp to get the equivalent.
Several month ago I decided to give LED a second chance. I bought those Philips 8W LED A19: http://www.homedepot.ca/product/8w-led-household-a19/926037
Yes, I know they look horrible but once you get over that they are well design and at the end it did calm down my grudge against LED lamp.
The Price of LED lamp is going down and the efficiency is going up if we are not there yet this is where we are going.
This was very helpful, thank you! You see, there was one variable you didn't account for: the annoyance of changing halogen bulbs. My condo kitchen track lights are 10 feet high and I don't have the right kind of ladder, which means changing them would be a big pain for me (especially as they never all burn out at the same time). I remember in my old place the halogens burnt out far faster than expected, but I couldn't help but wonder if the break even point with the LEDs would come soon enough to offset the time and irritating effort to change the halogens (and before I would move- don't see myself living there for the lifespan of the LED bulb). So your calculations made it easy to spend the money on four LEDS knowing I'll be saving myself considerable aggravation, as well as some money! Thanks again.
Halogen spot lights are favored as accent lights for the focused beam of light that they emit. When compared to conventional sources of lighting such as the incandescent and fluorescent bulbs, halogen bulbs are preferred as an energy efficient lighting source for residential as well as commercial purposes.
While trying to sort out the draw backs of halogen spot bulbs it is important to know how this basically works. Halogen spot lights are provided with tungsten filaments which when heated up produces light. The tungsten filament of the halogen spot light may undergo regeneration through a chemical reaction with the halogens. Since the filaments work at higher temperatures, the heat dissipation in halogen spot light is more and this is indeed one of its drawbacks. Since the tungsten filaments are placed much closer to the surface therefore reducing the surface area, the amount of heat generation is also more. Apart from this any vibration affecting the tungsten filament can cause permanent failure of the spot light. Led spot lights on the other hand are provided with light emitting diodes that are more effective than tungsten filaments.
LED spot light does not make use of filaments that are heated up during the working process to produce light. This means that heat dissipation in LED spot lights is comparatively less. Unlike in fluorescent lamps there is no use of toxic substances like mercury. LED spot lights are thus environment friendly and do not interfere with the surrounding objects either to harm them or distort their appearance.
Now let’s turn our attention to some statistical data that reaffirms the higher luminous efficiency of LED spot lights over halogen spot lights. The power dissipation of the most widely used models of halogen lamps like MR 16, par20 and GU10 are found to be between 20 W to 50W and their output in Lumens is between 160lm and 700lm. Further calculations based on the mentioned data, reveal that halogen spot lights have a luminous efficiency of 16% or in other terms the efficacy is 16lm/W.
Led spot lights on the other hand, are able to produce a higher output while consuming less electricity and are found to have a higher efficacy than Halogen spot lights. The same models of MR16,Par LED and GU 10 consume less electricity to produce the same amount of light than the halogen counterparts. With an in built three 1W power diode, LED spot lights can produce a light output of approximately 300 Lumens.
Led spot lights are able to focus its light without much wastage. The focusing of the LED spot light is fixed at 15degree, 30 degree and 45 degree beam angle so as to produce maximum usable light. But halogen spot light have a lesser service area need light compared to LED lamps.
Spot lights are normally meant for areas that are difficult to reach and a frequent replacement in that case would be a difficult task. The spot lights used therefore needs to be long lasting.LED spot lights are suited best in such a case as they have longer life span than halogen lights. A typical halogen light lasts for about 2000-3000 hours which may be equivalent of 3 to 4 months.
The light emitted by LED spot light is more bright, clear and crisp compared to the halogen light. There is no emission of CO2 in an LED spot light and makes it one of the most eco friendly systems.
Apart from these, more features have been added on to LED lights as researches progress and new functions are developed. LED certainly has an edge over the other lighting systems and spot lights are no exception. Get more details on http://www.kingbeehomes.com/led-lights-vs-halogen-lights/
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What also must be considered is the heat generated by each bulb in colder climates especially. I can get it a toasty 70 F in my bedroom with the door closed and my Halogen on when its 35 F outside. Good Article.
Love the graphs - they always explain things so much better than straight math. I did a similar analysis for my whole house recently - it's quite large, surrounded by tall trees and has a lot of lights that are on a lot of the time, so my payback was only just over 1 year.
I actually went to the trouble of replacing the whole oven hood (it was getting a bit past it though anyway) just so I could then install LED lighting. It used to make me wince knowing those 2 x 40W hood lamps were drawing nearly twice as much power as the rest of the kitchen lighting (long since all LED) combined. And they blew up at a fantastic rate. I've had 2 x 2W for over 2 years now and am really pleased with the light quality and 4W running cost.
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Ben,
Can you run your LED vs Halogen bulb calculation again but use 12 hours a day? Most of my clients are businesses, and their halogens are operating for 12-24 hours per day in lobbies, common area hallways, and office spaces. I think you'll find that the economics are much more compelling, and the reduction in kWh use when scaled over the vertical markets mentioned above is significant to say the least. Especially given the fact that most business sign 5+ year leases.
Thanks,
-Mike
Update #2! It really makes more sense for the data to by done per hour instead of per hypothetical 3 hour days. That's not exactly what you asked Michael, but you should be able to pretty easily figure out your 12 hours/day from that.
I wonder if you'll still be arround to see 11 leds.
Something no one ever talks about is that incandescents and halogens put 90% of their energy into heat so in a northern climate where we don't use much air cooling most of the electricity powering that bulb goes to heat my house so the bulbs are not as bad a deal as you make out, at least for some of us. On the other hand for those in southern areas you save twice, first to power the bulb and second power the airconditioner.
@John: Based on my 3/hrs a day of use, I can only expect to live long enough to have to change the LED bulb once. 🙂
If you assume for a 50W halogen bulb that 45W (90% of 50W) are being converted to heat, then sure- that'll help your furnace out a little. But how much of a little bit? Well, a small, energy efficient furnace has a power output (when on) of 60,000 BTU/hr- or about 17,600W. When it's really cold out, my furnace runs for 5 hours. This is a gross simplification, I'm sure, but 5 hours at 17,600 W is 316.8 megajoules of heat energy. Let's say I leave the 50W halogen on for 24 hours straight. The 45W over 24 hours is 3.89 megajoules or 1.2% of my heating. However, I'm estimating my halogen bulb is on for only 3 hours a day, which means the halogen is reducing my heating load by 0.15%. Sure, it helps reduce the heating bill, but it's probably a bad argument for keeping halogens over LEDs.
Interestingly, using the rough calculations and gross assumptions above, it'd take 82 of the 50W halogen bulbs burning non-stop to put out the same heat energy as my furnace. At least I wouldn't have seasonal affective disorder...
Please note it is now June of 2014 at the time of this post.
I am engaged in re-lighting our art gallery using over 160 fixtures (57 mr-16's using 50 watts (not sure of their lumens) & 106 so-called "spot-floods" (40 degree beam spread) also using 39 watts with an estimated life-span of 2500-3000 hours with lumens of 520.
I noted the date because the industry is changing so rapidly. I can now replace our spot-floods with an extremely similar LED using 15 watts, producing 770 lumens with a color rating index (c.r.i.) of 93...or 3000K on the light spectrum. Price: $15.99 plus tax.
Because an art gallery is pretty fussy about color accuracy, I decided to get gel material (called "1/8 straw") and glue a small circle of the gel on top of the glass lens to mitigate the slightly "whiter" than desired light. The gel knocks it down closer to 2750-2800K, a color we all are drawn to when looking at art. It also renders the artist's colors accurately.
The math of any savings seemed attractive. Even if the lights only last 7 of the predicted 9 years of life, we're still way ahead. We've calculated a 72.1% savings on wattage alone on all the lights. I'm not sure how to calculate our energy savings from reduced A/C use here in the very hot southwest, but from what I read, it can only be an improvement.
Color rendering is still challenging with LED's and not everyone is going to want to glue on gels as I am doing. But, it's getting better. And the LED lights we will use will be perfectly acceptable to many at a 93 c.r.i. And I won't even get into reduced carbon footprint as I don't have the numbers. It can only be good. This non-professional light guy is thinking that LED's are comin' on strong.
I was an 'early uptaker' of LED lamps, fitting one at top of flight of stairs to supplement two 'slow starting' CFLs. It died young, and shop would not replace it. {Spit !}
Recently, I've begun fitting nth generation LED lamps in places that are a real pain to reach, or to avoid excess heat generation. This includes a 'mini floodlight' replacing a rusty,old 'linear' halogen unit on garage wall that died in a flash, bang and cloud of steam. 150 W vs 10 W ? Amazing !! I can leave it on all night to help our cats hunt vermin...
The new mini-halogen replacements for ~60 Watt filament bulbs don't seem to last anywhere near as long as claimed. Even a pair in a dimmable fitting that does not get 'inrush' starts still die young. Still trying to find an answer to that, as dimmable LED bulbs are rather more expensive than basic types. And, yes, SBC types are rare...
One 'gotcha': The 'remote control', colour-changer LED lamps you can get eg via Amazon come in several brands, and a few offer actual multi-year guarantees rather than guesstimate hours of life. They're expensive, but that long warranty is a game-changer if you need to put a lamp in a really odd place...
Thanks for sharing this wonderful post. I agree with the author that the cost of led bulbs are a bit high in comparison to the halogen or the incandescent bulbs. But when one, looks at the various advantages, that it offers, the cost factor subsides down.
Coming to the advantages, led light bulbs can last up to 50,000 hours. This means, they have a longer lifespan in comparison to the halogen. Then these bulbs are effective in reducing the consumption of energy and also the electricity cost. Not only these bulbs are durable, but also Eco-friendly in nature.
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You share a really good information here, LED lighting provides many good features compared to the traditional light sources. LED lights are durable and energy efficient which made them the new technology that deserve to get a try.
Figure in the heat generation from a halogen, 325 degrees per halogen bulb versus 75 degrees for an LED.
We have 24 sockets in our kitchen and currently burning 50 watt halogen and it makes the kitchen noticeably hotter. I don't have the grey matter to calculate how many degrees it raises the room temp (volume, ambient temp, cost to cool/heat, etc.) but the initial outlay is killer to replace all at once!
LEDs may be costly upfront, but like renewable energy, it takes a bit of time for it to pay for itself. Nonetheless, LEDs are cost-effective and when we talk about longevity, LED is the big winner. Also, when we factor in the heat emission power of LED, we're really talking about cost effectiveness.
LED lighting is the way to go! Very cost effective and energy efficient. LED bulbs are very helpful across many industries.
Charles Dufour
http://www.illuminatedledmenus.com/
wife was on case as just installed LED Lighting threw out the house. after showing her you post she no longer giving me grief about the money spent as in the long run its a great saving.
pay peanuts get monkeys.
halogen is a better quality output of light.
if you want to live in a depressing cave under LED sterility then fine.
I noted your concern about electric bills...having just retired from 18 years of customer service for a North Eastern regional electrical utility, i thought i would pontificate on the subject since everyone else covered the technical data. It is called "unbundled". A certain percentage of our customers wanted to know, in detail, what went into their bills..given the PSC's desire to look like they are actually doing something, they required us to show detail... why, i have no idea as it doesnt change the total, and who cares how much is going to special causes... it dont change your total bill. Anyway, one useful change was separating the delivery charges from the supply charges so customers could see how much was the actual electricity itself vs how much to get it to your front door... this was useful to see if alternate suppliers would give you a savings... if they call, hang up, run screaming to the nearest closet, and barricade yourself in.
one of the stupidest splits was the cost to create and mail the bill. it was approx $.70. yeah. like people cared about $.70 vs a $200.00 supply charge.
of course, after we unbundled it, a certain percentage of people called to as why are our bills so complicated. and also why did we start adding these charges. which we didnt, they were always there, just bundled together.
That was a great exercise! I need to justify spending $24,000 for retrofitting 40-90 watt halogen commercial recess cans to a 42 watt Led using a retrofit kit for recess cans in a Church. The Zvhurch pays $0.10/kWh for electricity usage. How would that play out for a reasonable ROI? Thanks
Thanks again for the forum.Much thanks again. Fantastic.
Hi there,
I was looking this types of blog.I found your blog here.what a awesome post.I read your post attentively. Really you are a well writer.Your thinking and conception is real.All post is really helpful.ice to read.Because your blog is really attractive. Thanks for your creative activities.LED or light-emitting diode (LED) technology - to give its longer name - has been around since the 1970s and is becoming more and more prevalent for outdoor lighting effect of all kinds.Read more at here:led light fitting
Regards
SK
For the techies, here is an Excel spreadsheet where you can vary the parameters.
http://www.mediafire.com/file/1kbbzztk3daugkb/10_12_16.xlsx
Hii,
Thank you for sharing with us, such a great information. In these days of increasing energy prices, everyone is aware of energy saving light bulbs. Until recently filament light bulbs were in use in most homes but these have been phased out. I use energy saving light bulbs but I am not very keen on them.
But, When I switched on I noticed an instant difference. The bulbs seemed bright instantly, I did not have to wait for the light to warm up and reach full brightness. I also thought that the room seemed a lot brighter with less lights on. I was very pleased with the results and will be looking at changing the bulbs in my other rooms as well.
Regards,
Jerry James
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Please include Lumens, else i cant tell if your compareing a 100lm led bulb with directional light vs a 800lm halogen light.
Also i cant help noticeing on the packages it says 8000 hours on the led bulbs, instead of 25.000 or 50.000 as i see in advertisements.
5 years on and that LED bulb now costs negligibly more than the halogen lamp. That throws all your calculations off by a large factor. But in a good way.
Hi Ben, I was waiting for the last of 4 track lighting halogen bulbs to fail before replacing them all and thought to look up the expected life span. I found your post to be very helpful. I see now that there are GU10 LED bulbs available and will definitely get those instead.
In my search, I also found out that GE will discontinue manufacture of CFL bulbs in 2017.
Are your LED bulbs still working after 5 years?
Hi Guys, i actually do this for a living on huge industrial buildings, offices, arenas, curling clubs, MFG, food mfg.
the think you need to be aware of is the consumable lighting industry, the LED you are buying will not last its rated life, it will change color. Today most LED bulbs will have an effective life of 2-4 years. if you want proof i would be happy to share actual projects in which we are replacing LED 's that are 3 years old on average. you need to RETHINK how you buy lighting. Buy a system from a company with a real warranty who is truly accountable to it. http://www.thinkgreensolutions.com
This is a great comparative post. I love how long LED lights last.
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Superb analysis, thank you! There is still some degree of error in such calculations. E.g., I’d say about 1 in 10 LEDs would be broken much faster (maybe half its estimated lifespan)
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Smart tips! I’m very thankful I found your blog, I always wanted to save energy due to the high bill I’ve paid last month. It’s important to save money! Saving energy are both friendly to the environment as well as your utility bill.
You share a really good information here, LED lighting provides many good features compared to the traditional light sources. BAA LED Tubes are durable and energy efficient which made them the new technology that deserve to get a try
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These are really good information. I will soon be replacing all my downlights with LED globes/transformers as I have heard that is really effective in the longer term (although a bit costly to set up). BAA LED Tubes are durable and energy efficient which made them the new technology that deserve to get a try. Thanks for reminding me to get on with it!
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Electricity is only one of the costs. A greater cost can the the cost of replacement if a skylift is required to access it, but even a ceiling light replacement may require a trip to the store and a ladder not to mention the repeated requests to do it, the cost of the precious vase broken while handling the ladder or the medical bill after falling off of it and the value of the time spent figuring out how much one is saving. 🙂