What are the Most Energy Efficient Lights?

LED is by far the most energy efficient form of lighting technology of our generation. This technology has come a very long way since its inception.

The Light Emitting Diode (or LED for short) started its life in 1962 as a small electronic component. It wasn't until 1993 when physicists Isamu Akaski and Hiroshi Amano developed the first high brightness blue LED (leading to the white LED) that could be used for general lighting applications. And, it wasn't until 2002 that the LED became available for commercial use. More about the history of the LED can be found here.

In this article we’re exploring which LED lights are the most efficient in 2022.

What is Energy Efficiency?

Energy efficiency is about making the best possible use of the input energy when transforming it into output energy. French chemist Antoine Lavoisier (1743 to 1794) stated that, “Nothing is lost, nothing is created, everything is transformed.” Energy is transformed from one state to another and is not lost. It’s during the transformation process that energy efficiency can be calculated. I found some useful information about energy efficiency in this video:

 

While joules are used to describe international standard units of energy, we use watts to describe electrical energy. Energy efficiency within the lighting industry is more accurately described as energy efficacy. This is because efficacy takes more factors into account such as the total wattage required to power it. Some LEDs require an additional LED driver or a flourescent tube would require a ballast (like a voltage converter) for example; you would include these additional wattage to calculate the efficacy.

Then there is Light Output Ratio (LOR) which takes into account any light that is lost from the light fitting it's housed in. For example; due to the design of some light fittings, you might lose 10% of the light within the fitting, giving it an LOR of 0.9 or 90%.

To calculate the efficacy of a lighting product you divde the lumens by the wattage, so a 50 watt halogen at 350 lumens has an efficacy of 7 lumens per watt. This is a good way of comparing lighting products.

Halogen Example

A 50 watt halogen GU10 lamp transfers only 10% of energy into light, the remaining 90% is transferred into heat making it a grossly inefficient light source, which is why it's been banned. This diagram shows how the input energy is distributed or transferred.

While LED lamps will also transfer some energy into heat, let's say 10%, they are 90% energy efficient as you're getting 90% of light for your intended purpose.

Lighting Comparison

The 50 watt halogen GU10 emitted around 400 lumens, back in the days of the incandescent era everyone just ordered light bulbs by their wattage. It was only when LEDs became available that lumens become the more important factor. Lumens are the units that we measure brightness in. Most 5 watt or 6 watt GU10 LED lamps on the market emit around 400 to 500 lumens, it does depend on the brand and model your purchasing. The more technologically advanced 4.9 watt GU10 LED from Integral emits an impressive 600 lumens. Compared below are the lumens, efficacy and latest energy rating of a 50 watt halogen and 4.9 watt LED:

In the lighting industry we can use energy efficiency as a comparable measure and say that the LED is 90% more energy efficient. This is because it uses 90% less energy than halogen to produce the same lighting results. This is because it doesn't transfer energy into heat. Both sources produce around the same amount of light, while more advanced LED lamps are even more energy efficienct as they're brighter.

How much do LED Light Bulbs Cost to Run?

Let's take a look at three different examples and compare them with each other.

20x 50W Halogen GU10 Light Bulbs

I've chosen this specific example to keep things simple as it gives us 1000 watts, or 1kW. Here, in today's energy-hungry, lonely 'Great Britain' (where we barely do any of our own manufacturing and rely on other countries for energy resources) and taking into account the latest energy price increases from October 2022: I've calculated that if you've got 20x 50 watt halogen lamps running for 10 hours per day at 33 pence (or £0.33) per kilowatt hour (kWh), it will cost you £3.30 per day.

20x 4.9W LED GU10 Light Bulbs

In comparison, using the same quantity of 4.9 watt GU10 LED light bulbs (which equals 98 watts) you're only paying £0.32 per day while generating 12,000 lumens. Instead of paying £3.30 to generate 7,000 lumens. You're certainly getting better value for your money.

When you think about it, if this LED is 90% more energy efficient that the halogen, then it should cost you 90% less in energy costs, so £3.30 - 90% = £0.33. Which is 1 pence out.

20x 2.4W LED GU10 Light Bulbs

Now let's take things one step further with LED 2.0. While the 4.9 watt LED is very energy efficient, with an efficacy of 122 lumens per watt, it only gets an E rating from the 2021 rating system. Philips Lighting have very recently released a B rated GU10 which is the most energy efficient GU10 lamp on the market and will be for quite some time. This has an an efficacy of 158 lumens per watt, how much would 20x of these cost to run per day?

This level of energy efficiency is pretty amazing, but is the 16 pence day saving compared with the 4.9 watt really worth the extra investment? If you have your lights on for 10 hours per day, every day of the year (which is unlikley due to daylight hours) it will cost the following to run each option per year:

• £1204.50 to run the 50 watt halogens
• £116.80 to run the 4.9 watt LEDs
• £58.40 to run the 2.4 watt LEDs  

Purchasing 20x 4.9 watt Integral GU10 LEDs only costs £26.40 exc. VAT as they're priced at just £1.32 each, but purchasing 20x Philips 2.4 watt GU10 LEDs costs £251.80 exc. VAT as they cost £12.59 each - a difference of £225.40 exc. VAT. When LEDs first came onto the market, they were priced around this same level, new technology costs more.

With a modest saving of just16 pence per day, it will take you 1408 days (or 3.8 years) to really warrant purchasing the more energy efficient option of LED 2.0. The time period would be doubled if you only have them on for 5 hours per day, but halved if you run them for 20 hours per day, so the usage is an important factor. They are a great option for eco homes, or for people who want to be as energy efficient and as free from the electrical power grid as possible.

Energy Efficient Lighting

Lighting accounts for around 15% of the average household's electricity costs, so there are other areas in your home that you can look to reduce energy consumption such as heating and general electrical items like the dishwasher or fridge. If you've not already made the complete switch to LED, then now is certainly the time. If you've got one room with old halogen lamps, they could be costing you a small fortune to run. The decline in the pound is also leading to significant price increases from manufacturers in all industries, most businesses manufacture or source products from China but trade with the American dollar. The strong dollar and the weak pound isn't good for consumers.

Lighting Controls

Adding a dimmer switch to the circuit further reduces energy and increases lamp life. Smart lighting systems such as Lightwave gives you even more control as you can set timers and control all of your lights (and other electrical equipment) from your smartphone. The Lightwave App also shows you how much energy each smart switch, smart socket or heat switch is consuming in real time. You can install a smart motion sensor and set it via the App to switch your lights on and off automatically. Ultimately, the best way to be energy efficient is to avoid using it as much as you can.

Lighting Energy Labels Explained

When energy labels first started to appear on lighting products in 2012, they were a bit of joke as they had no scalability. LEDs had already reached an A+ rating, which meant any further improvements would become A+++++++, making the whole system seem ridiculous. In 2021 the system got redesigned downgrading a light source with a seemingly healthy looking A or A+ rating to an impoverished G rating shown below:

Bearing in mind that the light source remains the same in terms of energy consumption and lumens, only the energy rating changes. There are no more A+ ratings, once its reached an A, there is no room for improvement. More information about energy rating labels is available here on the Integral LED website.

Now to Unveil the Most Energy Efficient Lights...

With the current energy labeling system in mind there are only a few A-rated lamps available, these are going to be the most energy efficient. Like usual, Philips Lighting have been the fastest to produce them and have a few choices available in the filament or GLS (General Lighting Service) shape. Here they are, in order of the most energy efficient first:

With an ultra low 4 watt energy consumption, this offers a low energy alternative to a 60 watt incandscent and is available in warm white 3000K and cool white 4000K colour temperatures. Only available in the E27 Edison Screw cap. They also have a lower output version of this with a 2.3 watt = 40 watt version available here.

The most energy efficient GU10 lamp on the list is the Philips 2.4 watt, which is still somehow a 50 watt equivalent. Producing an impressive 380 lumens, it has an efficacy of 158 lumens per watt, putting it into the B classification. It does come with a reassuringly expensive price tag though, starting at £12.59 exc VAT which is like going back to the earlier days of LED lighting.

Next we have an energy efficient LED strip tape, with an energy consumption of just 4 watts per metre, it has a light output of up to 680 lumens per metre which gives it an efficacy of 170 lumens per watt. Because it consumes less energy, you can save some money on the LED driver as it doesn't need to be as big because the total wattage or load is less while still producing bright lighting results.

Down from the 2.4 watt option is the more pocket friendly priced Integral 4.9 watt GU10 which has a light output of up to 600 lumens and an efficacy of 122 lumens per watt. This gives it an E rating, which was A++ in the old system.

Then we have an integrated LED downlight from Collingwood Lighting with their H2 Lite 400 CSP model. This features a colour temperature switch with 3 colour temperatures in 1. At 4 watts, it produces 430 lumens and is a low energy alternative to a 50 watt halogen, but...in an integrated LED downlight format, where the LED itself is built around the downlignt housing to provide optimal lighting and energy efficiency results.

The EvoFire+ from Integral LED are an impressive and forward thinking design - the compact yet robust housing makes this LED downlight a contender for an innovation award but hybrid downlights have been here before. Now Integral have nailed it with a cost effective, replaceable LED module that you can change yourself, keep spares or change the colour temperature. They come with LED modules that can be replaced. This offers the best of both worlds, integrated technology with replaceable lamp modules. Available in a choice of finishes, colour temperatures and insulation coverable versions.

Thanks for reading, I've certainly learned a lot myself during this research process, light and energy are a combination of science, maths, history and technology. Without artificial light we wouldn't be able to work at night time. Light gives us a way of being able to put the extra hours in so we can afford to pay our excessive electrical bills!