LEDs use a fraction of the energy and last far longer, so the upgrade pays for itself. Two practical cautions: dimmers made for filament lamps often will not dim LEDs smoothly and may need replacing, and fittings with non-replaceable integrated LEDs are scrap when the LED fails. Choose fittings that take a replaceable lamp.
- Buy lumens, not watts. Watts measure consumption; lumens measure light.
- Colour temperature changes how a room feels more than brightness does.
- An old dimmer with new LEDs is the commonest cause of flicker and buzz.
- Integrated fittings cannot be re-lamped — the whole unit is scrap when the LED goes.
Reading the numbers
Decades of buying bulbs by wattage left most people without a feel for the figures that now matter.
| What | What it means | What to look for |
|---|---|---|
| Lumens (lm) | How much light is produced | The number that replaces watts |
| Watts (W) | How much power is consumed | Now just the running cost |
| Kelvin (K) | Colour temperature, warm to cool | 2700K warm, 4000K neutral, 6000K cool |
| CRI | How accurately colours render | 80+ acceptable, 90+ for kitchens and bathrooms |
| Beam angle | How wide the light spreads | Narrow for accent, wide for general |
| Dimmable | Whether it can be dimmed at all | Check, and check dimmer compatibility |
| Rated life | Hours before significant output loss | Tens of thousands of hours typically |
As a rough guide for replacing old incandescent lamps: around 400 lumens for a 40W equivalent, 800 for 60W, and 1,500 or so for 100W. Manufacturers usually print an equivalence on the box, and it is a reasonable starting point.
Colour temperature matters more than people expect
This is the decision that most affects whether people like their new lighting, and it is the one most often made by accident.
2700K is warm white, close to the old incandescent look. Comfortable in living rooms and bedrooms.
3000K is a slightly crisper warm white. A common compromise, and good in kitchens and bathrooms.
4000K is neutral white — noticeably cooler, good for task areas, garages and utility rooms.
5000K and above is daylight or cool white. Useful in a workshop, usually unwelcome in a living room.
The error that generates complaints is fitting 5000K lamps throughout a house because they look bright in the shop. The rooms feel clinical. The other error is mixing temperatures within one room or across adjoining open-plan spaces, which reads as wrong even when people cannot say why.
Decide the temperature per room, and keep it consistent within each.
The dimmer problem
The single most common complaint after an LED upgrade is flickering, buzzing, or lamps that will not dim below half and then switch off abruptly. Almost always the dimmer, not the lamps.
Old dimmers were designed for the substantial resistive load of filament lamps. An LED draws a tiny fraction of that, and the dimmer may not have enough load to work properly, or may be the wrong type for LED electronics entirely.
The fix is a trailing-edge dimmer rated for LED loads, with a minimum load that your lamps actually meet. It is a straightforward accessory change.
Two further points. Check the lamps are rated dimmable — many are not, and dimming a non-dimmable LED produces exactly these symptoms. And where one circuit mixes brands, dimming performance can be unpredictable; keeping a dimmed circuit to one lamp type is worth doing.
Integrated fittings: read this before buying
A growing proportion of LED fittings, particularly downlights and outdoor units, have the LED permanently built in. There is no lamp to change.
Manufacturers point to the long rated life, and the numbers are genuinely large. The practical problem is what happens at the end of it, or when one fails early: the entire fitting has to be removed and replaced, which on a downlight means ceiling access and on an outdoor fitting means rewiring the connection.
There is a second issue. Replace one integrated downlight in a row of eight several years later and the new one will almost certainly be a slightly different colour temperature and output. You end up replacing all eight for consistency.
Our standard advice: prefer fittings that take a replaceable lamp, particularly for anything in a ceiling or anything outdoors. You give up a little on slimness and pay marginally more, and you keep the ability to re-lamp for the cost of a lamp.
Downlights, heat and fire rating
Downlights are the fitting most often got wrong, and two requirements get overlooked.
- Fire rating. Cutting holes in a ceiling breaches its fire resistance. Fire-rated downlights contain an intumescent element that closes the aperture in a fire. They are required where the ceiling is a fire barrier — between storeys, or between a house and an integral garage.
- Insulation contact. Many fittings must not be covered by loft insulation, because they need airflow to shed heat. Covering them causes early failure and, with older halogen fittings, a genuine fire risk. Fittings rated for insulation contact solve this; otherwise a loft cap is needed.
- Spacing and quantity. The usual mistake is too many. LED downlights are efficient, and a ceiling peppered with them produces a flat, over-lit effect and costs more to install.
- Transformers and drivers. Where separate, they need to sit somewhere accessible and ventilated, not buried under insulation.
Repeated failures of downlights in one position almost always indicate heat or a connection problem at that point rather than a run of poor lamps.
Where the saving actually comes from
An LED uses roughly a tenth of the power of the incandescent lamp it replaces and lasts many times longer. Both parts matter, and the second is often the larger saving in practice — particularly for fittings that are awkward to reach.
Where to prioritise: the lights that are on longest. A kitchen or living room used every evening repays the change far faster than a loft light used twice a year. Outdoor and security lighting that runs all night is another obvious candidate.
Halogen downlights are the clearest win of all. A dozen 50W halogens in a kitchen ceiling is a serious load running for hours a day, and replacing them typically cuts that by around ninety per cent.
What we would not do is replace perfectly good working lamps everywhere at once purely to save energy. Change them as they fail, and prioritise the heavy-use fittings — unless the fittings themselves are being replaced for other reasons, in which case do it properly in one go.
What it costs
These are the electrical figures published across this site:
| Job | Typical Coventry guide price | Notes |
|---|---|---|
| Typical job | £233–£473 | Sockets, lighting, faults |
| Electrician, hourly | £45–£90/hr | Certified, Part P |
| Consumer unit upgrade | £450–£700 | RCD protection |
| EICR (3-bed) | £150–£300 | Safety certificate |
Swapping lamps is usually something you can do yourself. Changing fittings, adding downlights or replacing dimmers is electrical work, and like sockets it is far better value bundled into one visit.
We will check dimmer compatibility, specify fire-rated and insulation-safe downlights, and steer you away from fittings you cannot re-lamp.
Frequently asked questions
Why do my LED lights flicker when dimmed?
Almost always the dimmer. Old dimmers were designed for the large resistive load of filament lamps, and an LED draws a tiny fraction of that — so the dimmer may not have enough load to operate correctly or may be the wrong type entirely. A trailing-edge dimmer rated for LED loads normally fixes it. Also check the lamps are actually rated dimmable.
Can I just swap my bulbs for LEDs?
In most standard fittings, yes — match the cap type and choose by lumens rather than watts. The cases needing more care are dimmed circuits, low-voltage fittings with transformers that may not suit LED loads, and enclosed fittings where heat build-up shortens LED life. Those are worth checking rather than assuming.
What colour temperature should I choose?
2700K warm white for living rooms and bedrooms, 3000K for kitchens and bathrooms, 4000K neutral for garages, utility rooms and task areas. Avoid 5000K and above in living spaces — it reads as clinical. Most importantly, keep it consistent within a room and across adjoining open-plan areas.
Are integrated LED fittings worth avoiding?
We generally recommend fittings that take a replaceable lamp, especially for downlights and outdoor units. Integrated fittings cannot be re-lamped, so the whole unit is scrap when the LED fails, and replacing one in a row years later gives you a visible colour mismatch that usually means replacing them all.
Do downlights need to be fire rated?
Where the ceiling forms a fire barrier — between storeys, or between a house and an integral garage — yes. Cutting holes in such a ceiling breaches its fire resistance, and fire-rated fittings contain an intumescent element that closes the aperture in a fire. Separately, check whether the fitting is rated for contact with loft insulation.
How much will I save switching to LED?
An LED uses roughly a tenth of the power of the incandescent it replaces, and lasts many times longer — the reduced replacement cost is often the bigger saving, especially for awkward fittings. Prioritise lights that are on longest. A kitchen full of 50W halogen downlights is the clearest win available.
Lighting that works, not just lighting that is cheaper
We check dimmer compatibility, specify the right fire and insulation ratings for downlights, and avoid fittings you cannot re-lamp in five years.