What Watt LED Replaces 50W or 100W Halogen? (UK 2026 Guide)

Switching from halogen to LED lighting is one of the easiest ways to cut your electricity bill. But one of the most common questions homeowners ask is:
What watt LED replaces a 50W or 100W halogen bulb?
The short answer:
50W halogen = 5–7W LED
100W halogen = 10–15W LED
But wattage isn’t the most important number anymore — lumens are.
In this guide, we’ll explain exactly how to choose the correct LED replacement, what brightness you actually need, and how much money you’ll save by switching.
Why Wattage No Longer Matters (It’s About Lumens)
Halogen bulbs were measured by wattage because more watts meant more brightness.
LEDs are different.
They use far less energy to produce the same brightness. That’s why you should compare lumens, not watts.
Here’s a quick comparison chart:
Halogen Wattage
LED Equivalent
Lumens (Brightness)
35W
4–5W
300–400 lm
50W
5–7W
400–500 lm
75W
8–10W
700–900 lm
100W
10–15W
900–1300 lm
So if you’re replacing a 50W GU10 halogen, look for an LED producing around 400–500 lumens.
LED Equivalent for 50W Halogen
If you currently use:
50W GU10 spotlight
50W MR16 bulb
50W outdoor floodlight
You’ll want:
5W–7W LED
Around 450 lumens
Matching beam angle (usually 36° or 60°)
💡 Pro tip: Always check lumens first, then wattage.
LED Equivalent for 100W Halogen
For larger fittings such as:
Outdoor security lights
Large floodlights
Bright kitchen or workshop fittings
You’ll need:
10W–15W LED
Around 900–1300 lumens
For security lighting, many UK homeowners actually choose 1500–2000 lumens for better coverage.
How Much Money Will You Save?
Here’s where LED really wins.
Example:
Replacing one 50W halogen with a 6W LED:
If used 4 hours per day:
Halogen yearly cost ≈ £14–£18
LED yearly cost ≈ £2–£3
That’s around 80–90% energy savings.
Now multiply that by 10–20 bulbs in a home.
Switching to LED can easily save £100–£300 per year in electricity.
GU10 LED vs Halogen: What to Watch For
When replacing GU10 halogen bulbs, check:
✔ Lumens (not watts)
✔ Colour temperature (2700K warm white vs 4000K cool white)
✔ Beam angle
✔ Dimmable compatibility
If your old halogen was warm and cosy, choose 2700K–3000K LED to match the feel.
Common Mistakes When Switching to LED
Choosing based on watts instead of lumens
Buying the wrong colour temperature
Ignoring dimmer compatibility
Choosing too narrow a beam angle
These mistakes often lead people to think LEDs are “too bright” or “too harsh.”
Is It Worth Replacing Halogen With LED in 2026?
Absolutely.
LEDs:
Last 10–20x longer
Use up to 90% less electricity
Produce less heat
Are safer
Reduce maintenance costs
With rising UK energy prices, switching to LED is one of the simplest long-term savings upgrades.
Quick LED Replacement Checklist
Before buying, check:
✔ Fitting type (GU10, MR16, E27, etc.)
✔ Required brightness (lumens)
✔ Colour temperature
✔ Beam angle
✔ Indoor or outdoor rating
✔ Dimmable or non-dimmable
Final Thoughts
If you’re replacing:
50W halogen → choose 5–7W LED (~450 lumens)
100W halogen → choose 10–15W LED (~1000 lumens)
Focus on lumens, match your colour temperature, and you’ll enjoy lower bills and better lighting instantly.