DALI vs DALI-2: What UK Engineers Must Know in 2026

Why DALI-2 Is Now the Default, Not an Upgrade

DALI and DALI-2 share the same two-wire bus. Same wiring, same voltage. So why does the distinction matter so much in 2026?

The answer is straightforward: the DALI Alliance (DiiA) ended registration of DALI version-1 control gear in May 2022. Any new project specified today must use DALI-2 certified gear. There is no grey area here.

For UK engineers, the stakes go beyond protocol preference. The 2021 revision to UK Building Regulations tightened lighting control requirements for commercial installations, making controls specification a compliance issue, not a technical nicety. With the UK LED lighting market valued at roughly £2.5 billion in 2025 and smart lighting expected to account for 30% of the market by 2026, getting this right is a growing commercial priority.

This article maps the three-tier hierarchy: DALI version-1 (legacy), DALI-2 (current standard), and D4i (future-proof for smart buildings). Use it as your decision tree for every specification scenario you face this year.

What DALI Version-1 Actually Covered (And What It Didn't)

DALI (Digital Addressable Lighting Interface) is an open, bi-directional digital protocol standardised under IEC 62386. Introduced in the late 1990s as a replacement for analogue 1-10V dimming, it gave engineers addressable, two-way control of individual luminaires on a simple two-wire bus.

DALI version-1 covered control gear only: ballasts, LED drivers, emergency modules, and dimmers. That was the full scope. Sensors, push-buttons, occupancy detectors, and bus power supplies were not included in the standard at all.

This created a significant gap. Manufacturers who wanted to offer sensors or keypads for DALI systems had to develop proprietary solutions, often labelled "eD" controls. These devices sat outside the standard entirely, and interoperability between brands was unreliable.

There was a second, less obvious problem: self-declaration. DALI version-1 relied on manufacturers declaring their own compliance. No independent testing was required. A product could carry the DALI logo without any third-party verification that it actually behaved correctly on the bus.

DALI version-1 supported up to 64 control gear devices on a single bus but had no standardised framework for control devices whatsoever. In practice, a "fully DALI" installation could still contain proprietary, incompatible components at the sensor and controller level. Many UK buildings still running legacy DALI systems have exactly this problem.

What DALI-2 Actually Changes: Certification, Coverage, and Commands

The most common misconception is that DALI-2 is a new protocol. It is not. DALI-2 is a certification programme, launched in 2017 by the DALI Alliance (DiiA), built on the restructured IEC 62386 standard updated in late 2014. The underlying bus technology is the same.

DALI-2 makes two fundamental changes:

1. Independent third-party testing is now mandatory before any product can carry the DALI-2 logo. Self-declaration is gone.
2. Expanded device coverage brings control devices into the standard for the first time.

DALI-2 adds application controllers and input devices to the ecosystem: push-buttons, occupancy sensors, light sensors, and absolute input devices. All of these were entirely absent from DALI version-1.

The architectural expansion is significant. DALI-2 supports up to 64 control gear devices and up to 64 control devices on the same bus, doubling the addressable capacity of a single DALI line compared to the version-1 framework.

At the command level, DALI-2 introduces 14 new commands while removing one outdated command. Extended fade times are included, enabling smoother, more precise dimming transitions.

Several critical application areas are now formally standardised under DALI-2:

• Part 207 — Dimming
• Part 209 — Colour control (essential for human-centric lighting in offices, healthcare, and education)
• Part 202 — Emergency lighting

None of these were formally standardised under DALI version-1. For UK commercial projects, Part 202 alone makes DALI-2 certification a compliance requirement, not a preference.

Backward Compatibility: What You Can Keep and What Must Go

The backward compatibility position, stated plainly: legacy DALI version-1 control gear (drivers, ballasts) will operate in a DALI-2 installation, but only within their original functionality. They will respond to basic commands, dim, and report status as they always did.

What they will not do is support any DALI-2 features. Extended fade times, new commands, and energy reporting will not be available on legacy version-1 devices. They function, but they do not gain new capabilities.

The critical on-site risk lies elsewhere. Pre-DALI-2 sensors, push-button interfaces, and keypads (the proprietary "eD" controls mentioned earlier) are not compatible with DALI-2 application controllers. These must never be mixed on the same DALI line. This is the single most common cause of commissioning failures in mixed installations, and it catches experienced engineers out more often than expected.

There is a second hidden risk: bus power supplies. Pre-DALI-2 bus power supplies carry no DALI version-1 trademark, and their compatibility with DALI-2 systems is uncertain. Engineers must verify compatibility before reusing any legacy bus power supply in an upgraded system.

For phased migration, the practical guidance is clear:

• Retain legacy DALI version-1 drivers where they are functional and budget is tight.
• Replace all control devices (sensors, keypads, controllers) with DALI-2 certified equivalents.
• Never assume a legacy sensor will work with a new DALI-2 controller. Test or replace.

D4i: The Bridge Between DALI-2 and Smart Buildings

D4i (DALI for IoT) is an optional extension of DALI-2, introduced by DiiA in November 2019. Every D4i-certified driver is also DALI-2 certified. D4i is DALI-2 with mandatory data layers built in.

Those data layers are:

• Part 251 — Luminaire asset data (identity, type, installation date)
• Part 252 — Energy reporting (real-time power consumption at luminaire level)
• Part 253 — Diagnostics and maintenance (operating hours, failure alerts)

Part 252 is directly relevant to UK Net Zero 2050 targets and the 2021 Building Regulations revision. Lighting accounts for approximately 15% of total electricity consumption in UK commercial buildings. Native energy reporting at luminaire level makes D4i a compliance tool, not just a smart feature.

D4i also simplifies installation. Sensors can be powered directly from the DALI bus via an integrated bus power supply within the driver itself, eliminating the need for a separate power supply at luminaire level and reducing wiring complexity and cost.

D4i-certified LED drivers from brands such as Tridonic, Osram/Ledvance, Philips/Signify, and Helvar are the go-to choices for future-proof commercial retrofits. LED Retro stocks genuine components from these manufacturers with same-day UK dispatch.

For wireless retrofit scenarios, the same DALI-2 or D4i certified drivers can be paired with Bluetooth mesh (Part 341), Zigbee (Part 342), or Thread (DALI+) gateways. This is particularly valuable for UK retrofit projects in listed buildings or occupied spaces where re-cabling is disruptive or not feasible.

Specifying DALI-2 in 2026: A Practical Decision Framework

Here is how to approach specification decisions across the most common UK project scenarios:

New-build commercial projects: Specify DALI-2 certified gear throughout. With DALI version-1 registration closed since 2022, there is no justification for specifying legacy gear on any new installation.

Retrofit with legacy DALI drivers: Retain existing DALI version-1 control gear where it is functional, but replace all sensors, keypads, and controllers with DALI-2 certified devices. Never mix eD or proprietary legacy control devices with DALI-2 application controllers on the same bus.

Energy reporting required (client brief or building regulations): Specify D4i-certified drivers. This is the only way to deliver native energy data at luminaire level without bolting on third-party metering.

Wireless retrofit (listed buildings, occupied spaces): Specify DALI-2 or D4i drivers with a compatible Bluetooth mesh or Zigbee gateway. This avoids re-cabling entirely while maintaining full protocol compliance.

Emergency lighting compliance: Ensure all relevant control gear is certified to DALI-2 Part 202. This is a critical compliance area for UK commercial projects and one that is frequently overlooked in specification documents.

Colour and circadian control (offices, healthcare, education): Specify DALI-2 Part 209 certified gear for human-centric lighting applications. Colour tunability under a standardised protocol is only available through DALI-2.

Specifying with Confidence in 2026

The three-tier hierarchy is straightforward: DALI version-1 is legacy, DALI-2 is the current standard, and D4i is the future-proof choice for smart building integration.

Since May 2022, DALI version-1 registration has been closed. DALI-2 is not optional for new specifications. It is the baseline.

The two most common on-site pitfalls in mixed installations remain eD sensor incompatibility and unverified bus power supplies. Both are avoidable with proper specification and component verification before installation.

Specifying DALI-2 and D4i certified gear from trusted brands is the lowest-risk path for UK commercial projects in 2026. LED Retro stocks genuine DALI-2 compatible drivers and D4i LED drivers from Tridonic, Osram/Ledvance, Philips/Signify, and Helvar, all with same-day UK dispatch and free delivery on orders over £50. For guidance on the right driver for your project, our technical team is available to help.