Did you know that in 2014, the Nobel Prize in Physics was awarded to the three guys who invented the blue light-emitting diode (LED)? Why such an important prize for just one of the colors on a string of Christmas lights?
In the spirit of Thanksgiving, let’s take a minute to understand and appreciate the impact of their work—the solution to a problem they spent years of their lives working to solve.
It turns out that—for technical reasons I don’t understand—we’d had red and green LEDs for a long time (picture an old alarm clock), but it was really difficult to make blue LEDs. And if you ever looked up close at an old CRT television screen, you probably know that when you combine red, green, and blue light sources together, you can make white. So once we had blue LEDs, the missing puzzle piece fell into place, making possible everything from LED TVs to the insanely tiny and bright flashlight on the back of your phone.
But by far the most important application of the new white LED was the reinvention of the humble lightbulb. Because LEDs use dramatically less energy than incandescent bulbs, and less even than compact fluorescents, switching out your old bulbs is a quick way to start saving energy. And because LED bulbs have gotten dramatically cheaper since their introduction, they’re now so affordable that they will pay themselves back in energy savings very quickly.
Let me repeat that: LEDs are cheap, super efficient, and will pay themselves back in no time flat. Every month for years after that, the bulbs will be paying you in savings. And making the switch is literally as easy as—well, changing a lightbulb.
There aren’t a lot of decisions in life that are this simple. Search your house for incandescent bulbs and replace them with LEDs today. Don’t wait for them to burn out.
Not convinced? What about your compact fluorescents? Let’s talk for a second about electricity math.
Understanding Electricity Usage
Whether you realize it or not, you probably already associate lightbulbs with the mathematical unit that measures power: the watt. If you’re old enough to be reading this article, you’re probably old enough to be familiar with common incandescent bulbs such as the 60-watt or 100-watt. In practical terms, you might think of them as brightnesses, but they’re really a measure of how much power the bulb consumes.
And unless you’ve never once looked at your electric bill, you’ve probably also heard the term “kilowatt-hours,” or kWh. What’s the relationship to watts? Let’s break it down:
- A kilowatt is 1,000 watts. Because, you know, the metric system.
- A kilowatt-hour is you using 1,000 watts of electricity for one hour. This unit exists because without a unit of time involved, electricity bills wouldn’t make any sense.
So let’s do some quick math. If you turn on a 60w bulb and leave it running 24/7 for 30 days, you will have used:
60 watts x 24 hours x 30 days = 43,200 watt-hours of electricity, or 43.2 kWh.
According to the U.S. Energy Information Administration, the national average cost-per-kWh for residential customers in August 2021 was $0.1399, or about 14 cents. At that rate, burning one 60w bulb 24/7 for a month costs you:
43.2 kWh x $0.1399 = $6.04.
Elementary school math, right? I know it’s unrealistic to run a bulb 24/7 like that (or at least I hope it is), but let’s stick with it for the purpose of comparison. OK, let’s see what happens when we switch that 60w bulb out for a compact fluorescent (CFL). Now, a “60w equivalent” CFL is going to produce about the same amount of light as a 60w incandescent—that’s the “equivalent” part—but only use about 13w.
You can do all that same math again, or you can take a shortcut: 60w is 4.6 times greater than 13w, so running this CFL 24/7 for 30 days will cost you 4.6 times less than $6.04, or $1.31.
So what about LEDs? Well, a 60w-equivalent LED—again, that’s a brightness comparison—only uses about 8.5w, a reduction of about 1/3 from a CFL, and 7 times less than an incandescent.
Now we’re talking $0.86 to run a lightbulb nonstop for a month. Even though I know you wouldn’t do that, I bet you do have a ton of lightbulbs in your house, so you can imagine how the savings add up. To sum it up, big picture:
- If somehow you’ve still got a house full of incandescents, replacing them with LEDs will mean spending 7 times less to light your home.
- If you’ve got a house full of CFLs, replacing them with LEDs will mean spending about 33% less to light your home.
When to Replace Your Lightbulbs with LEDs
So you probably already figured out based on the above that you should replace your incandescents with LEDs ASAP. Like, tomorrow. But what about your CFL bulbs? If you’re like most people, your house probably has a mixture of both.
To help visualize the money math, I made this graph:
The graph shows the cumulative cost of running all three types of bulbs for three hours a day. I included the average cost of a new LED bulb today ($1.35) in the cost of running the LED, which is why the green line starts above $0. I didn’t include the cost of a CFL or incandescent because you already own those.
Notice how quickly the LED pays itself back relative to an incandescent—the moment the green line crosses the red line at about 60 days, that LED bulb you bought is free. And while you should still burn it as little as possible, every day you use it after that you’re essentially getting extra money in your pocket—money that you used to be spending on lighting your home with incandescents.
And that’s if you run your light for just three hours a day. If your bulb is going for six hours a day, the payback will happen twice as quickly.
So what about CFLs? Well, notice that those two lines don’t cross within the first year. In fact, at three hours/day you have to run this experiment out to about the two-year mark for the LED’s energy savings over a CFL to cover that $1.35 purchase price. (Or if you run your bulb for more like six hours a day, the one-year mark.)
This is where you need to start thinking about the lifespan of a lightbulb.
How Long Do LEDs and CFLs Last?
CFLs are expected to last, on average, about 10,000 hours. That’s a little over 9 years at 3 hours/day. For reasons I don’t understand, LEDs seem to vary a little more—you’ll see 60w-equivalent bulbs with a 7-year lifespan, or up to an 11-year lifespan (both at 3 hrs/day). Either way, you’re doing a lot better than with incandescents, which top out at around 1,000 hours—which is basically one year of use.
Stop and try to absorb about how amazing this is. Not only are LED bulbs extremely efficient to operate, they last for years. So you save money on your monthly energy bill and you save money on replacement bulbs.
Anyway, do a little thinking about your CFLs—how long ago did you buy them, and how much do you use them? If your CFL is probably going to burn out in the next year or so, you might as well wait it out. If you just put new CFLs in within the last couple years, you have more to gain by replacing them with LEDs sooner.
Bonus: How LEDs Help Your Old Home’s Electrical System
A final reason to switch that you don’t hear talked about as much are the benefits LEDs can bring to your house’s electrical system. Essentially, by using less power, they also make more “space” within your system for you to safely run appliances and other things.
At your electrical panel, or breaker box, you’ve got a couple dozen individual circuit breakers. Each of those breakers is responsible for killing the power to a particular electrical circuit in your house if it gets overloaded—i.e., if something on the circuit draws too much power. I lived in an apartment once where this happened if I ran the microwave while I used the toaster, and I’m sure you have a similar story. It’s annoying, but it also helps keep your house from burning down.
In newer construction that’s been wired according to newer standards, in theory there is a lot of logic in how many circuits a house has and what those circuits serve. But in old homes, there’s a good chance that your circuits were run based largely on convenience, such as what was accessible in the existing construction. The result is often that one circuit covers many rooms in your house—the lights in your kitchen, the receptacles (outlets) on your back porch, and somehow also your TV in the attic.
The point is, it can be hard to know how heavily loaded your circuits are when you don’t know exactly what they serve within your house. LEDs help with this by practically taking your lighting out of the equation entirely.
You can tell the capacity of each circuit by looking at the number on the breaker, which is rated in “amperes” or amps. Amps are a measure of current, which is sort of like power (measured in watts). The most common circuit breakers are 15-amp and 20-amp, meaning they’re designed to trip if the current being drawn on the circuit reaches that number.
So how much current do lightbulbs draw? I’ll spare you the math (which is simple but a subject for another article). At your house’s 120 volts:
- A 60w incandescent draws 0.5 amps.
- A 13w CFL draws 0.1 amps.
- An 8.5w LED draws 0.07 amps.
As you can see, even power-hungry incandescents don’t draw a huge amount of current. A single 15-amp circuit can safely handle at least 24 of those 60w bulbs.* That might be enough to cover all the lights in your whole house, so why are we even talking about this?
Well, because if you own an old home, there’s a good chance that a single 15-amp circuit serves a mixture of light fixtures and receptacles in a number of rooms. Say it’s summer, and you have a couple window units plugged in and blowing A/C. Then you plug in your vacuum cleaner—boom. You tripped a breaker!
Making sure your incandescents are replaced with LEDs will reduce the lighting load on your circuits by 7x—just like it will bring the lighting portion of your electricity bill down by 7x. A circuit with six bulbs will go from drawing 3 amps to drawing less than 0.5 amps. That’s what I meant when I talked about making “space” in your electrical system. A few amps’ worth of extra overhead can make the different between being able to run your vacuum cleaner or window unit in an old home.
This little bit of extra headroom might have other benefits, depending on your situation. In my house, most of our ceiling lights were installed in the 1920s on four separate circuits. Due to the extremely low load of LED bulbs, I was able to combine those into one circuit, freeing up three other breakers. If you’re somebody with a 100-amp panel who has worried you’ll need to shell out for a new 200-amp panel for the extra capacity, switching to LED bulbs just might allow you to delay or prevent that upgrade entirely.
TL; DR: Make the Switch
Do yourself a favor and make a quick audit of your house’s lightbulbs. Tally up any incandescents and whether they’re 60w, 100w, or something else. Also tally up any CFLs that you think you installed more than a few years ago, or that you definitely use for many hours a day.
Take those numbers and order yourself LED bulbs in the appropriate wattages today. (That’s an affiliate link. If you like the look of incandescent bulbs, you’ll probably want to order 2700K LEDs. More on that later.) Install them as soon as you can. You’ll thank yourself—and those three Nobel-prize-winning dudes—later.
*Assuming a maximum load of 80% of the rated capacity.