Record the lamp type, cap or tube length, wattage and any driver or dimmer details before you shop.
LED replacement guide
LED wattage comparison: find the right replacement for your light
Replacing an older lamp is easier when you separate power use from light output. Use this guide to compare common LED wattages with older bulbs, tubes, floodlights and downlights, then check lumens, dimensions, colour temperature and the installation conditions before ordering.
The useful answer
Compare light output first, then confirm the physical fit.
An LED wattage comparison is a starting point. Wattage describes electrical power, while lumens describe light output. The replacement still needs the correct cap, tube length, dimensions, voltage and installation arrangement for the fitting already in place.
Use the confirmed lumens, colour temperature, dimensions and product rating rather than wattage alone.
For fixed wiring, outdoor fittings and tube replacements, follow the exact product instructions and use a qualified electrician where required.
Start with the fitting
The old wattage is only the first check.
A replacement is a good fit when the lamp shape, cap or tube length, light output and installation method all make sense for the existing space.
Check the tube length, fitting type and whether the existing installation is compatible with the LED tube you choose.
Compare LED tubesFor bulbs and downlights, compare lumens and colour temperature rather than using wattage as a brightness promise.
Browse LED bulbsFloodlights need their own check for IP rating, beam spread, mounting position and the area that must be covered.
Browse LED floodlightsThe quick comparison
Use these figures as a starting point, not a substitute for lumens.
| LED category | Common older reference | Useful starting point | Check before ordering |
|---|---|---|---|
| LED tube | 18W, 30W, 36W or 58W T8 fluorescent | 7W, 10W, 15W or 20W LED tube | Length, tube feed, fitting compatibility and lumen output |
| LED floodlight | Halogen or metal-halide floodlight | Choose by area, beam and lumens, not wattage alone | IP rating, bracket, voltage, beam angle and outdoor exposure |
| LED bulb | Incandescent or halogen bulb | Compare the old wattage with the LED lumen output | Cap, shape, dimensions, CCT and dimmer compatibility |
| LED downlight | Halogen downlight | Compare wattage, lumens and cut-out size | Cut-out range, ceiling depth, IP rating and driver arrangement |
Why two bulbs with the same wattage can look different
Wattage tells you how much electrical power a lamp uses. Lumens tell you how much light it produces. Colour temperature changes the appearance of that light, while beam angle and diffuser shape change where it lands. Use the product listing for the confirmed lumen output and installation facts rather than assuming every replacement behaves the same way.
Verified ways forward
Move from a comparison to a product that suits the job.
These live products show how the same broad replacement question becomes different once the room, weather exposure and installation details are clear.
For damp or semi-exposed utility areas
The 590mm fitting is listed at 18W, 1500 lumens, 6500K daylight and IP65. It is a different decision from a bare replacement tube because the complete fitting and its dimensions matter.
View the weatherproof fitting
For a protected T8 installation
This IP65 stainless steel fitting is 1310mm long in the single 4 foot format and is listed for use with an LED tube. The tube is not included, so match the two parts before ordering.
View the T8 fitting
For a warmer outdoor floodlight
The Nano Evo is listed at 10W, 1000 lumens, 3000K and IP65, with a 360 degree adjustable bracket. It suits a different brief from replacing an indoor lamp.
View the outdoor floodlight
For a visible decorative bulb
This A60 E27 bulb is listed at 6.5W and 804 lumens with a warm white 2700K output. It is dimmable with a compatible dimmer and intended for indoor use.
View the A60 bulbBefore you buy
Four checks that prevent the wrong replacement.
Match the physical fit
Check cap type, tube length, overall dimensions and downlight cut-out. A lower wattage does not help if the lamp cannot fit the existing holder or opening.
Match the light level
Use lumens as the brightness reference. For downlights, the live listing for the adjustable model gives different wattage and lumen options, so select the correct variant.
Match the environment
Indoor IP20 products and outdoor IP65 products are not interchangeable. Confirm the exposure, mounting position and product rating before installation.
Match the controls
If the existing fitting uses a dimmer, sensor or special driver, confirm compatibility with the exact product. A bulb described as dimmable still needs a compatible dimmer.
Unsure which replacement is compatible?
Send the old lamp type, wattage, dimensions, a photo of the fitting and the space where it is installed. Future Light can help narrow the category before you order.
Common questions
What to check when the chart does not settle it.
Can I replace a 36W fluorescent tube with a 15W LED tube?
That can be a useful starting comparison, but confirm the tube length, wiring or fitting arrangement, lumen output and installation instructions for the exact product.
Is a higher wattage always brighter?
No. Wattage measures power use. Compare the confirmed lumen output, beam angle, diffuser and colour temperature for the application.
Can I use an indoor LED bulb outside?
Only when the complete fitting and product are confirmed as suitable for the exposure. Indoor and outdoor ratings should not be assumed to be interchangeable.
What should I send for a compatibility check?
Share the existing lamp type, cap or tube length, wattage, dimensions, a clear photo and the room or outdoor location. Those details are more useful than wattage alone.