T5 or T8 LED Tube? Differences & Comparison
Published November 15th, 2025
Advantages of GLT LED TUBE T5/T8 at a glance
130.000 h
service life
IEC EN 62776
1:1 replacement T5/T8
-40°C bis +70°C
industrial-grade
up to 80%
energy saving
What are the differences between T5 and T8 tubes?
“T” stands for “tubular”, referring to the tube shape. The number indicates the diameter in eighths of an inch. T5 fluorescent tubes have a diameter of 16 mm and a pin spacing of 5 mm, while T8 fluorescent tubes have a diameter of 26 mm and a pin spacing of 13 mm.
👉 While this distinction was relevant in fluorescent lighting technology, it no longer has any technical significance for LED tubes and LED retrofit systems.
T8 LED tubes
T8 tubes are fitted with end caps for G13/G8 sockets (13 mm pin spacing).
T5 LED tubes
T5 tubes are fitted with end caps for G5 sockets (5 mm pin spacing between the pins).
Which LED tubes can replace T5 or T8 fluorescent lamps?
T5 and T8 fluorescent tubes are replaced by corresponding LED tubes with the same socket type and matching length. To ensure a safe and compliant 1:1 replacement, these products must fulfil the requirements of IEC/EN 62776.
Legal basis: IEC/EN 62776 (Glossary)
The international IEC/EN 62776 standard forms the legal basis for the compliant 1:1 replacement of fluorescent tubes with LED tubes. It defines the safety requirements for LED tubes operated directly on 230 V mains voltage without a control gear (direct mains connection).
Among other aspects, the standard specifies requirements for electrical safety, interchangeability within existing lamp holders, permissible operating conditions and testing procedures under real operating conditions.
👉 EN 62776 is a harmonised standard and serves as the basis for CE conformity of LED retrofit conversions within the EU. It provides a reliable framework for continuing to use existing luminaires and fittings while upgrading to an efficient, low-maintenance and future-proof LED lighting system.
Which LED tube is compatible with my luminaire?
Whether a T5 or T8 LED tube is required depends entirely on the existing luminaire or fitting. The following criteria are decisive:
Socket type in the luminaire or fitting
- A luminaire with a G5 socket requires a T5 LED tube.
- A luminaire with a G13/G8 socket requires a T8 LED tube.
Length of the luminaire or fitting
The second key factor is the luminaire length. This is determined by the existing fitting and defines the compatible LED tube length. Typical standard lengths are:
- T5: 549 mm / 849 mm / 1149 mm / 1449 mm
- T8: 590 mm / 1200 mm / 1500 mm
👉 Conclusion: The length and socket type of the luminaire (G5 or G13/G8) determine which LED tube is suitable for a compliant replacement.
Standardised fluorescent tube lengths
The following table shows the most common fluorescent tube lengths together with the corresponding LED replacement options using the GLT LED TUBE.
Which retrofit methods are available?
Existing lighting installations use different types of control gear designed for the operation of fluorescent tubes. Although LED tubes do not require control gear, the existing system configuration influences the retrofit process and conversion effort.
Typical systems include conventional control gear (CCG), low-loss control gear (LLCG) and electronic control gear (ECG).
In professional applications, the control gear is removed or electrically bypassed, and the LED tube is operated directly on 230 V mains voltage. Solutions that continue to operate with CCG/LLCG or ECG are generally considered technically inferior in terms of efficiency and operational reliability.
Costs & Return on Investment
LED tubes can deliver significant energy savings, in many cases up to 80%. At the same time, maintenance requirements are substantially reduced due to the much longer service life (up to 130,000 hours with the GLT LED TUBE).
👉 The key factor for economic efficiency is therefore not the purchase price, but the overall assessment of energy consumption, service life and failure risk.
Fluorescent Tube Phase-Out
The phase-out of T5 and T8 fluorescent tubes has been in effect since 24 August 2023. These products fall under the EU RoHS Directive (glossary) regulating the restriction of hazardous substances in electrical and electronic equipment. Since that date, the European Union has prohibited the production and placing on the market of mercury-containing light sources such as fluorescent tubes.
Existing installations may continue to operate under grandfathering provisions. However, defective lamps may only be replaced with RoHS-compliant light sources. Otherwise, the CE conformity (glossary) of the entire lighting installation may be put at risk.
The 4 most common mistakes when replacing T8/T5 LED tubes
Is the LED tube compatible with the existing luminaire?
To maintain CE conformity*, fire protection compliance and E-Check certification, it is essential to use a compatible LED light source. The LED tube must fulfil the requirements for LED retrofit in accordance with IEC/EN 62776* and match the existing lamp holder.
Has the wiring been implemented safely and in compliance with standards?
High-quality LED tubes feature an integrated driver and operate directly on 230 V mains voltage. External control gear is professionally rewired and decommissioned in accordance with applicable standards. Incorrect rewiring creates safety risks and negatively affects the efficiency and functionality of the lighting system.
Is the service life being assessed correctly?
Alongside energy efficiency, service life is the most important quality and economic factor of an LED tube—and therefore of the entire lighting system. The longer the service life, the higher the product quality and the lower the maintenance and replacement costs. Very low-cost LED tubes typically fail earlier and generate higher total costs over time.
Is the system energy efficiency being evaluated correctly?
System efficiency (the overall energy efficiency of the lighting installation) is, alongside service life, the greatest economic lever for reducing long-term operating costs.
Mistakes to avoid when retrofitting to LEDMistakes to avoid when retrofitting to LED
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Glossar
*CE (Conformité Européenne)
Das CE-Kennzeichen steht für „Conformité Européenne“, auf Deutsch „Europäische Konformität“. Es handelt sich um eine rechtlich verpflichtende Herstellererklärung. Mit dem Anbringen des CE-Kennzeichens bestätigt der Hersteller, dass das betreffende Produkt alle geltenden EU-Richtlinien und EU-Verordnungen erfüllt, die für seine Produktgruppe relevant sind. Im Fall von Leuchten und Leuchtmitteln sind das insbesondere Richtlinien zur elektrischen Sicherheit, elektromagnetischen Verträglichkeit sowie zur Ökodesign-Richtlinie.
*Norm IEC EN 62776
Die internationale Norm IEC EN 62776 definiert alle technischen und sicherheitsrelevanten Anforderungen, die beim Austausch von zweiseitig gesockelten Leuchtstofflampen (G5 und G13) auf LED-Röhren in bestehenden Systemen einzuhalten sind. Sie beschreibt, wie die Umrüstung fachgerecht erfolgt, welche Komponenten stillgelegt werden müssen und wie der normgerechte Betrieb mit einer LED-Röhre direkt an 230 V sichergestellt wird. Sie regelt die:
- elektrische Sicherheit
- Austauschbarkeit & Prüfverfahren
- zulässige Betriebsbedingungen
*RoHS (Restriction of Hazardous Substances)
Die RoHS-Richtlinie 2011/65/EUDie RoHS-Richtlinie 2011/65/EU ("Restriction of Hazardous Substances")RoHS-Richtlinie 2011/65/EU ("Restriction of Hazardous Substances") beschränkt innerhalb der EU gefährliche Stoffe in Produkten, wie zum Beispiel Quecksilber in Elektro- und Elektronikgeräten. Die Einhaltung der RoHS-Richtlinie ist die Voraussetzung für die CE-Kennzeichnung von LED-Leuchtmitteln, LED-Leuchten und LED-Beleuchtungssystemen, da sie den Einsatz bestimmter gefährlicher Stoffe in elektrischen und elektronischen Produkten begrenzt.