Low Energy Lighting (LEL)

At the time of writing this page, the methodology for EPC assessments of existing dwellings is RDSAP 10. A significant methodology overhaul from RDSAP to the Home Energy Model (HEM) is proposed for 2026 and government consultations indicate proposed changes to the format of EPCs and minimum rating levels required for private rental properties. Methods for improving EPC ratings will therefore change in the future.

I remember the old traditional tungsten filament bulbs we used to have when I was a child, and how hot they ran. They'd blow regularly, and we'd have to unscrew them with a double-folded tea towel before fitting a new one.

Also, the light fittings and cables would brown over time because of the long-term exposure to heat and need replacing periodically.

Light fittings back then were rated by the maximum power of bulb they would accommodate, limited by the amount of heat generated, and you'd have to be careful with that because some domestic bulbs ran at 150W.

Imagine today how much power would be drawn if you had 10 of those all powered up at the same time.

Things have changed, and as part of the drive to reduce energy usage and CO2 emissions the sale of standard bayonet tungsten filament bulbs in the UK is prevented by legislation. Even T8 fluorescent tubes in the UK are on their way out too.

For energy efficiency reasons the move for some time has been towards what is called 'Low Energy Lighting', with LED being the most efficient.

Lighting is included in EPC assessments and it can affect the rating, so this encourages uptake of the most efficient forms.

For a better EPC rating the goal is essentially to have all of your lamps as LED rather than anything else.

The way that lighting is assessed changed slightly on the 15th June 2025 with the introduction of RDSAP 10.

The main difference is that all lamps are now assessed individually.

There is a Convention that instructs how lighting should be assessed and this reads as follows:

Convention 7.01

"Consider all lamps (bulbs or tubes) in permanent fittings within the dwelling. Include fixed under-cupboard kitchen lights. The Number of lamps is counted (not the number of fittings).

• Only LED lamps are recorded as LED
• Any Fluorescent Tubes and Compact Fluorescent lamps are recorded as CFL
• Tungsten and Halogen lamps are recorded as Incandescent (i.e. are not low energy)
• LED strips are counted as one lamp per running meter (rounded to the nearest meter)
• If an individual lamp is missing, or the lamp type cannot be identified, record as CFL
• If more than 50% of the lamps which are not Incandescent cannot be identified or are not present, record all non-incandescent lamps as LEL."

So, every lamp is counted, and of these, the number of LED lamps and CFLs (Compact Fluorsecent Lamps) is separately noted.

A chandallier which would previously have been counted as 1 light fitting now requires a count of all the lamps.

Previously where 4 or more spot lights were in the same room, the count would have been halved (so 6 spotlights would have been counted as 3). Now every lamp is counted instead.

Only lamps inside the property are counted. Lamps outside the property and in parts of the property that are not included in the assessment are not counted. This includes unheated garages, thermally separated conservatories, room in roof that does not fulfill the room in roof criteria etc.

Portable fittings are also not counted, such as standard lamps and table lamps.

Importantly, notice in the convention above that Halogen bulbs are considered alongside 'traditional' tungsten filament bulbs in terms of performance.

Also, as mentioned above, any missing lamp will be considered as a CFL.

The RDSAP 10 Specification document describes the recommendation which can appear on your EPC certificate to improve the efficiency of your lighting.

The recommendation:

• Is considered when the dwelling is: a new or existing dwelling
• Is triggered if: LEL < 100% of fixed outlets [I think there is a typo here and it should read 'of fixed lamps']
• Shows the rating when proceeding with: "LEL in all fixed outlets with efficacy 80 lumens/Watt (15W) (LEL includes LED and CFL bulbs)".

In addition, supporting information advises that:

"A recommendation is made only if it increases the SAP rating by at least 1 (one) SAP point, or 0.5 SAP point in the case of C (cylinder insulation), D (draughtproofing) and E (LEL). These thresholds may be overridden by amended values in the PCDB."

So, the above recommendation will only appear if it makes at least a 0.5 SAP point increase to the EPC rating.

Lighting is one of the elements listed in the Features table on EPCs, alongside walls, floors and roofs etc.

Here is an example of a features table from an EPC produced under the current RDSAP 10 methodology

We can tell this is an RDSAP 10 EPC by presence of the option to include an air tightness test result.

The way the 'Rating' textual description for lighting is determined has been updated and this is now based on the average efficacy of the lighting.

The textual description is now 'harsher' than before and many clients experience an emotional response when viewing the description on their EPC, and comparing it for example with a previously expired EPC.

The criteria that distinguishes between the three rating descriptions is as follows:

When calculating the average lighting efficacy, RdSAP10 uses the following default information for each type of lamp:

• LEDs = 100 Lm/W (9W)
• CFLs = 55 Lm/W (19W)
• Incandescent = 11.2 Lm/W (60W)

Alternatively, if the separate number of LEDs and CFLs is not known, then the default is used:

• LEL = 80 Lm/W (15W)

Let's work through some examples to illustrate how this works and how sensitive the textual Rating description is when non-LED lamps are present.

Consider the case where we have 20 lamps in total.

Example 1

Clearly, if all 20 were LED, the average lighting efficiency would be 100 lumens per watt and the rating description would be 'Very Good'.

The calculation however is quite sensitive to anything that is not LED so let's try another example to illustrate this.

Example 2

This time, we have 20 lamps, of which 18 are LED, 1 is a CFL and one is an incandescent.

We multiply the quantity of each type of bulb by the default power:

LED = 18 x 9W = 162W

CFL = 1 x 19W = 19W

INC = 1 x 60W = 60W

The total electrical power here is 162W + 19W + 60W = 241W

Next, the lumens:

LED = 18 x 100 l/W x 9W = 16,200 Lumens

CFL = 1 x 55 l/W x 19W = 1,045 Lumens

INC = 1 x 11.2 l/W x 60 =  672 Lumens

The total here is 16,200 + 1,045 + 672 = 17,917 Lumens

Dividing Lumens by Watts we get 17,917 / 241 = 74.3 L/W

This would give us 'good lighting efficacy'.

Example 3

This time we have 20 lamps of which 18 are LED and 2 are incandescent. So 90% of the lamps are LED.

LED = 18 x 9W = 162W

INC = 2 x 60W = 120W

The total electrical power here is 162W + 120W = 282W

Next, the lumens:

LED = 18 x 100 l/W x 9W = 16,200 Lumens

INC = 2 x 11.2 l/W x 60 =  1,344 Lumens

The total here is 16,200 + 1,344 = 17,544 Lumens

Dividing lumens by watts gives us 17,544 / 282W = 62.2 l/W

This would give us a Rating textual description of 'Poor'. Remember this is where 90% of the lamps are LED and 10% are incandescent.

The takeaway is, don't spend any time thinking about the Rating textual description, life is too short. The overall rating will not have been affected very much and there are far more important things to focus your attention on.

Let's take the 3-bed terraced house covered in our Case Study 1 page where we have 11 lamps. Here are the results from changing the proportion of LED lamps fitted:

We can see for this house that moving from 0 to 100% LED would take us from a 71C to a 74C, which is an improvement of 3 SAP points.

This is a fairly decent increase, but it's likely that most properties will already have a fair proportion of LED lamps fitted, thus making the potential improvement available smaller, however it's a measure that is easy to implement and should be completed as a matter of course.

Those one or two or even three SAP points here could be the ones that take you up a band from say a D to a C if you were already on the threshold, so considering the ease of effort and low cost, this is the first step that most homeowners will complete.

In summary, upgrading your lighting to LEDs, the most efficient lighting type, is an easy step to take and doesn't cost much money.

This should be carried out as a matter of course before an EPC assessment is conducted.

This measure only makes a small difference to your EPC rating, particularly if you already have a reasonable proportion of LEDs fitted.

It could however make the difference that takes you up into the next rating band if you are already on a band threshold.

Click here to return to our 'Improve Your EPC' main page, and see if there is another way you could improve your EPC rating.