How Many Reasons Does It Take to Change a Light Bulb?

How Many Reasons Does It Take to Change a Light Bulb?

1024 675 Seth Terry

Introduction and Context

We’ve probably all experienced it: a light bulb too hot to touch.  Although we turn lights on to combat the dark, we cannot avoid the release of heat.  Generally, we view this heat as harmless.  However, sometimes we feel that heat more unpleasantly – like when we burn fingertips on a lamp or bake under bright lights in a kitchen or on a stage.  The heat of course represents inefficiency in the production of light.  We all recognize that perfect efficiency is not possible.  However, until the last decade or so, most of the bulbs used in our homes relied upon the same technology developed by Edison in 1879.   Known as black-body radiation, this method for making light actually relies on high temperatures to emit photons.  But now, a new, more efficient, and “cooler” way to produce photons is widely available: light-emitting diodes (LEDs).  And being cool is just one of the reasons to change your light bulb!

Ready to Buy LED Replacement Bulbs Now?

Perhaps you have already heard enough reasons to motivate changing out some light bulbs. If so, we have curated our favorite and most popular selections here. But if you’re not quite ready or want to learn more, please keep reading below!

Research Summary

Until recent years, LED bulbs that fit common household sockets were relatively expensive.  However, today LED bulbs are often no more costly than older style bulbs – and can last 10 to 20 times as long.  Because of their greater efficiency, LEDs produce about four times more light output per watt.  Better yet, they generate less unwanted heat in the process. 

Nevertheless, the majority of us have yet to make the switch to LEDs. 

With respect to lighting, the US Department of Energy suggests that simply changing out the five most often used bulbs or fixtures in a home can save $75 per year.  For a typical electricity consumer, this amount equates to about 5% savings.  However, many of us can realize greater savings by replacing further bulbs – though not necessarily all of the 60 bulbs or so found in most homes. 

Happily for LED users, the benefits of greater efficiency extend beyond the lighting function.  In a classic example of “good following good,” avoided heat output saves money on climate control as well.  In northern climates, these savings may wash out with additional heating requirements in winter.  But many buildings could experience net savings on the order of 20% for air conditioning through decreased heat output from lighting

Emporia Savings Calculations

Emporia calculates savings for LED replacement as falling between 5% and 10% of electrical consumption.  As indicated above, this amount is likely conservative given the additional savings found in LED replacement.  Specifically, the avoided cost of purchasing bulbs over time and the avoided cost of cooling. Doubtless, there are numerous reasons to change your light bulb!

Just as with other savings calculations, the more often a user opens the Emporia app, the higher will be their savings.  And the more you engage, the better your chances of attaining 50% energy savings!

Do Your Own Math!

As noted beforehand, the US Department of Energy provides the simple guideline of changing out the “five most often used bulbs.” However, given the low price of many new LEDs, this general rule may leave savings on the table for many homeowners! Therefore, can we develop a more thorough approach, perhaps giving economic reasons to change that old light bulb?

The answer, of course is YES!

The formula below tells us the number of hours of LED bulb use required for energy savings to equal the cost of the new bulb. In other words, it tells us how long it takes for savings to pay back the original cost of the bulb: the payback period. For this reason, this type of formula is known as a “payback calculation.”

The Payback Calculation Formula for LED Bulbs

Where:

Application of the Formula

Let’s try a simple example calculation looking at a “standard” bulb replacement. Historically, the most common bulb in any of our homes is likely an “A19” 60-Watt incandescent lamp-bulb. If we replace this old-school bulb with an LED bulb designed to provide similar lighting, the power requirement is only 8 Watts. Therefore, the Power Difference Between Bulbs = [60 W – 8 W]/1000 W/kW] = 0.052 kW.

A non-dimmable LED light bulb to replace a 60-Watt incandescent may be found for as low as $1 from recognized name-brand manufacturers (click here to purchase these bulbs). Therefore, we will use Bulb Cost = $1.00 in our formula. This leaves Energy Cost as the only remaining term for our formula. The average cost per kWh for electricity in the US is 12.9 cents — or $0.129/kWh.

Using these inputs, we use our formula to calculate the following payback period:

1 kWh = [$1.00] / {[$0.129/kWh] * [0.052 kW]}
  1/0.00671
  149 hours

Wow: 149 hours. Typically, projects are evaluated on payback periods stretching over YEARS! This is why upgrading to LEDs generally represents such a favorable project. That said, be aware that this result applies to actual operation of the bulb — and you may not run every bulb in your house for 149 hours this year — or next. Therefore, we really ought to consider an appropriate time horizon to make the most rational decision around replacing lighting.

Relevant Time Horizon

With that in mind, it is interesting to take into account our intended length of stay in a home where we might upgrade lighting.

One Year…

Perhaps we only intend to rent a home for a single year. In this case, we would consider averaging out the calculated 149 hours over 365 days. To wit, 149 hrs / 365 days = 0.408 hrs/day = 24.5 minutes/day. This means that you will make money over that year by replacing every 60-W incandescent bulb that you estimate running for more than 24.5 minutes on a daily basis. This certainly means any landscape or security lighting and probably means kitchen lights, bedroom lights, and many bathroom lights.

…Leads to Another

But what if your decide to stay in your rental for another year? Now, we are looking at dividing our 149 hours by 2 * 365 = 730 days. Suddenly, our average daily use threshold moves from 24.5 minutes to just over 12 minutes! And of course, if this pattern repeats for a third year, we are the average daily use threshold drops to just about 8 minutes.

With this pattern firmly identified, we should consider that the average homeowner stays in a home for about seven years. With this length of stay in mind, most of us should replace any bulb that will run for more than 3.5 minutes daily. Now we’re getting into the realm where MOST lights should be replaced right away!

On a personal note, I have now been in my home for 15 years. Using the logic above, I have replaced all but the most rarely used bulbs in my house (for example: the guest room closet). And since I am likely to remain in my home for years to come, I now replace ANY bulb that burns out with a new LED. This includes even all under-counter lighting (which originally was hot, hot halogen!). Click here to purchase these great bulbs.

Or Let Us Do the Math for You!

At Emporia, we strive to emphasize positive customer experience. In this manner, we have built the following calculator for your convenience.

LED Replacement Calculator

ParameterValueUnits
Old Bulb Wattage:Watts
New Bulb Wattage:Watts
New Bulb Cost:dollars
Electricity Cost:cents/kWh
Anticipated time in home:years

Hours until payback: 0 hours

Daily use threshold: 0 minutes

 

Purchase Your Replacement Bulbs

Again, in the name of convenience, we have curated an easy, short list of what we view as the best and most common replacement bulb options. Click here to see them!

A Few Final Notes

Dimmability, Durability, and Brightness

Dimmable vs. Non-dimmable

You may have noted a distinction made when introducing the low-price LED replacement lamp bulbs earlier in this article. Specifically, they were called out as non-dimmable. When purchasing LEDs, one should note whether a dimming switch controls the bulb. For these cases, dimmable bulbs should be purchased to avoid premature failure of the LED bulbs.

Bulb Life

As long as you follow the caution above, you should anticipate significantly longer life from LEDs than for the hot bulbs replaced. That said, even LEDs emit some heat and their lifespan decreases when operated at high temperatures. Typical estimates for the lifespan of LEDs range from 10,000 to 30,000 hours. This value compares favorably to the lifespan of traditional incandescent bulbs, which generally endure for 1,000 to 1,500 hours. That’s 10 to 20 times longer — if not more! This and other reasons make a bulb change to LED light bulbs an excellent choice in locations with difficult access, such as high chandeliers and security fixtures.

Color Temperature

As a further benefit, you can generally expect improved brightness from LEDs as well. Consequently, LEDs can help fill gaps between “can” fixtures as well as improve lighting in such areas as closets or garages. Again: so many good reasons to change that light bulb!

However, prior to purchasing replacement LED light bulbs, it is important to note that this new technology allows for a broad range of “colors.” Often, we think of these colors as reflective of the warmth of the lighting. To aid our understanding of color, it helps to return to the beginning of this post. Recall that the physics of black-body radiation provided the basis for producing light from heated metal filaments. Measured in degrees kelvin (K), the lower the temperature, the warmer (or redder) the light. Higher temperatures correspond to whiter light (think “white hot”). As examples of the range in colors, candles typically emit at about 1,900K while about 5,600K corresponds to daylight at noon. Be aware that the lamps available through our store generally fall in the range of 2,500K to 3,000K, which mimics the warm light of many incandescents formerly in our homes. Many of these bulbs are also available in whiter light through the same links. But note: the higher K lights also contain more blue light, which may interfere with sleep patterns.


Seth Terry

Seth is Head of Customer Experience at Emporia Energy. A Colorado native, Seth has devoted his career to working in the water-food-energy nexus and remains deeply committed to meeting the challenge of climate change.

All stories by:Seth Terry