Ultimate Beginner’s Guide to Energy Saving Light Bulbs

By Lindsay Wilson on 5 February 2014

This is an edited version of an article that was originally published on Shrink That Footprint. Edited and reproduced with permission.

Five years ago I bought my first LED light bulbs. They were to replace halogens in my bathroom. I spent too much money on not enough lumens and way too many kelvin. You know what I mean?

No? Perfect. Let’s make a deal?!

If you spend 10 minutes reading this post I promise you that by the end of it you’ll understand how to buy a low energy light bulb. In return I’ll try not to bore you senseless.

Ready? Let’s do this. With five simple questions.

1) What fitting do you need?

This is simple, but you really don’t want to mess it up.

Although there are literally hundreds of light fittings in existence, your home probably only has a couple. I’ve got two in my ceiling fittings, a couple more in table lamps. In the image below there are some common examples.

common light fittings

'B' is for Bayonet, it's a bit of a British Empire thing. 'E' is for Edison Screw, dominant in the US thanks to Thomas. 'GU' is for, gee you really need to get yourself a life a if you know what 'GU' means.

You don't need to know what they mean. But if you scribble down the fittings before you start shopping for bulbs not only will they fit, they'll be the right voltage too.

2) What shape bulb do you want?

Bulb shape is not just a question of liking the look of a bulb, it is about how it throws light. The design of the bulb determines what direction the light goes, so you need to consider what you want the bulb to do.

bulb shape

There is literally an alphabet describing different bulb shapes, but since I promised not to bore you I’m just not going to go there. All you need to do for shape is use your common sense.

For a ceiling pendent you might want an 'omnidirectional' bulb like the arbitrary, stick or spiral shape. For a lamp you might need a candle shape with a broad spread. And if you are putting a spot into a recessed downlight you'll need a reflector with an appropriate beam width for the context.

A bulb that throws the wrong angle light can be really annoying, so do take the time to contemplate the shape before you buy.

3) How bright does it need to be?

It is no longer enough to think about bulb brightness in terms of watts. That was fine when we only had incandescents, but now we need to start thinking in lumens.

This is particularly the case when buying LEDs, because the use of the term 'replacement' can be abused by bulb re-sellers, and occasionally by lesser manufacturers too. The following tables are a rough explanation of how many lumens you get from your watts for different bulb technologies for a standard fitting.

Now I'm very sorry to do this, but I had to make two charts to explain this properly. One for our readers in the low voltage (120V) countries like the US, Canada, Brazil and Japan. And a second one for readers in high voltage (240V) countries, that’s the rest of the world.

The Australian Lumen:

In certain parts of the world, like Australia, grids have higher voltage (240V), meaning that lumen equivalent for standard incandescents is as follows:

Lumens needed

At the top of this chart you have the brightness of the bulb in lumens. This is the number you need to start thinking in.

So, if you’re in Australia, and want to replace an old 60W bulb and get a similar amount of light, then you know you’ll need to get at least 700 lumens to get a similar brightness to the old bulb.

Knowing your lumens means you will get the brightness you want, and avoid being mis-sold 'replacement bulbs'.

A quick word on spotlights:

Just spot me a second here. Both the two charts above are designed to help you replace a normal light bulb. When it comes to spotlights you can often experiment with going for fewer lumens. In our bathrooms I have replaced 700lm halogens with 320lm LEDs and actually prefer the light. The result is a 90% energy use reduction per bulb.

4) Do you want warm or cold light?

This question might sound complicated, but it is dead easy and one of the great things about LEDs.

The temperature of light can be measured in terms of 'kelvin'. Very orange light has a low number of kelvin, for example a candle is about 1,500K. Daylight is much colder, often above 5,000K. Here is the scale.

kelvin scale lightbulbs

When it comes to household light bulbs the temperature choices are very simple. Most people simply want what is called 'warm white' (2,700k) to replicate the warm, slightly yellow glow of an old incandescent or halogen.

In a kitchen, bathroom or other situations you may prefer a slightly less yellow light, sometimes called a natural white (3,000K). You may want to try cool white (4,000K). Or for a very specific style (5,000K). Anything above that starts to get a little blue.

This type of temperature choice is mostly associated with LEDs. If your home has a quite modern style you should definitely consider trying some cooler temperatures, as they can look great in the right context.

5) Are LEDs good value yet?

Compact fluorescent (CFLs) bulbs are now so cheap that a CFL can pay itself off with energy savings in just months for a well used bulb. I personally quite like CFLs in the right context, but if you want instant light, dimming or cooler light they aren't great.

LEDs on the other hand are gradually overcoming many of these problems. The main issue with LEDs at this point is their upfront cost. This is particularly true for 75W and 100W replacements (I'm waiting for prices to drop).

With this in mind let's crunch some numbers and see how the payback is for LEDs. In the following chart I estimate how quickly energy savings will recoup the cost of replacing a 60W incandescent with a 10W LED that costs $10, assuming the bulb is used for 2 hours each day.

LED payback times

Because of the huge difference in the prices of electricity the $10 outlay for the LED pays itself off in anything from 9 months in expensive Denmark to three and a half years in India or China, where electricity is cheap.

Of course a 60W LED for $10 is still quite cheap. If it costs you $20 to get such a bulb you'd need to double these numbers. On the other hand if you are using the bulb 4 hours a day, then you should halve them. What does this mean for you in practical terms?

  • Cheaper LEDs payback faster
  • Payback is faster where electricity is expensive
  • The more you use a bulb the faster the payback
  • Replacing CFLs with LEDs is not yet cost effective

In most cases the one year running cost of an incandescent bulb you use regularly (>2 hours a day) is greater than any drop in LED prices we are likely to see. So it makes sense to switch when you see a decent value bulb. However, if you don't use a bulb much (< 1 hour a day) you may want to wait for falling prices. Especially in the 100W replacement range which are still extortionate.

I have one incandescent left in my loft that I'd be lucky to use for 10 hours a year. I'll probably only switch it if it blows.

5 Steps to Buying a Energy Saving Light Bulb

If you’ve made it this far you now know a lot about light bulbs. Because I promised not to bore you I've decided not to discuss dimming (read the labels), colour rendering (above 80 please) and bulb lifespan (buy a known brand).

Let's just recap the five steps:

  1. Fitting: Write down the code
  2. Shape: Decide on the best shape
  3. Brightness: Get enough lumens!
  4. Temperature: Warm or cool?
  5. Cost: Look for good value bulbs

Like I said in the introduction, I bought my first LED five years ago and only really got the first of these five steps correct. But things have changed an awful lot in five years, and LEDs are now becoming a really sensible option. CFLs remain excellent value due to their low prices and running costs, but you can’t always get the light you want.

If you have never bought LEDs before I highly recommend trialling a single bulb, or spotlight, first before buying too many. LEDs are not cheap and last a long time, so you want to be sure about fitting, shape, lumens and kelvins before going all in on them. I also recommend looking for specials on known brands or having a money back guarantee up your sleeve.

If you made it to the end, thanks for reading. I wish you much success with your LED hunt and hope you get the right fit, shape, brightness and temperature at a decent price. Most importantly I hope you prefer the light of your new bulb, as that is the main test of success.

This post is one of the efficiency projects connected to our How to Save Money on Electricity video program. Check it out.

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