The short answer
Replacing fluorescent lighting with LED typically saves around 30–60% of lighting energy, and replacing metal halide high bays often saves 50–70%. Complete commercial upgrades commonly pay back in two to five years, faster where lights are on for long hours.
Typical savings by lamp type
| Existing lighting | Typical LED saving | Notes |
|---|---|---|
| Fluorescent T8/T5 | 30–60% | Efficient T5 systems may save less |
| Metal halide high bays | 50–70% | e.g. 430 W including gear replaced by 150 W |
| High-pressure sodium (SON) | 30–60% | More with dimming or reduced hours |
Compare like with like: the new lighting should deliver the light level the space actually needs, and the old system's ballast or control gear losses should be counted.
How to work out payback
Simple payback is the installed cost divided by the yearly saving. The saving is the watts saved per fitting, multiplied by the number of fittings and the hours a year they are on, multiplied by your electricity unit rate.
Example: a £100 installed LED panel replacing a 72 W fluorescent panel with a 36 W LED saves 36 W. At 2,500 hours a year that is 90 kWh. At 25p per kWh the saving is £22.50 a year, so the energy-only payback is about 4.4 years. Longer hours, higher tariffs and fewer lamp changes shorten it.
Our LED savings calculator does this sum for your own figures.
Savings beyond the electricity bill
- Fewer lamp changes and less high-level access in tall buildings.
- Instant start, so no waiting for metal halide or sodium lamps to warm up.
- Easier dimming and sensor control.
- Better colour rendering than sodium, which helps workshops and CCTV.
Questions
Do LED tubes in old fittings save as much?
Not always. Retrofit tubes leave old holders and sometimes ballasts in circuit. A complete LED luminaire is usually more efficient and more reliable.
Related services
LED lighting upgrades
Swap fluorescent, halogen and metal halide fittings for efficient LED.
Warehouse lighting
LED high bays and aisle lighting for warehouses and distribution sites.
Lighting controls
Presence detection, daylight dimming and DALI systems.
Office lighting
Glare-free LED lighting for desks, meeting rooms and receptions.
Last reviewed 9 November 2026. This guide is general information, not legal, tax or engineering advice for a specific site.