Getting an LED upgrade signed off feels like the end of the project. In most commercial buildings, it’s treated that way. The installer hands over documentation, the old fittings go to WEEE disposal and the lighting drops off the facilities agenda — sometimes for years.
The problem is that LED lighting performance can and does change over time. Energy savings drift. Light levels fall. Controls get misconfigured after building changes. What delivered full ROI in year one may be quietly underperforming by year three. A post-install commercial lighting audit finds out where you actually stand.
Why LED Lighting Performance Can Drift Over Time
LEDs don’t fail the way older lamps did. They don’t burn out suddenly. Instead, output degrades gradually — a process called lumen depreciation. The industry standard for measuring this is the L70 rating: the point at which a fixture’s output has fallen to 70% of its initial level. For most commercial LED products, that threshold is reached at around 50,000 hours. On a standard 10-hour operating day, that’s over 13 years.
The catch is that 70% is the rating threshold, not a cliff edge. In practice, light levels can drift meaningfully below the installation baseline long before that point — particularly if the original design included a tight maintenance factor, or if the building environment accelerates depreciation. Dust and dirt accumulation on diffusers and reflectors can reduce effective output without any fault in the fitting itself.
Controls misconfiguration is a separate issue. Presence sensors get knocked out of calibration. Daylight zones get disabled after complaints and never re-enabled. Time schedules get altered during a refurbishment and never restored. The result is higher energy consumption than the upgrade was specified to deliver, with no obvious failure to trigger a review.
Changes to how a building is used also matter. A space that was a meeting room when the lighting was designed may now be a task-intensive workstation area. The same lux levels that were appropriate then may no longer meet the requirements in HSG38.
Signs Your Commercial Lighting May Be Underperforming
| Symptom | Likely cause | Business impact |
| Areas feel noticeably dimmer than before | Lumen depreciation or dirty diffusers | Below HSG38 lux levels; compliance risk |
| Complaints of glare or eye strain | Controls changed; poor uniformity | Staff fatigue; HSE wellbeing concern |
| Flickering in certain zones | Driver age or compatibility issue | Distraction; potential H&S issue |
| Energy bills haven’t fallen as expected | Controls misconfigured or overridden | ROI not being delivered |
| Inconsistent colour between fittings | Mixed products from reactive maintenance | Poor environment; staff experience |
| Emergency lighting not recently tested | No documented test regime in place | BS 5266 compliance risk |
If you’re seeing two or more of these, a lighting efficiency audit is warranted.
What a Post-Install Lighting Audit Checks For
A professional commercial lighting audit covers the following:
Lux level measurements: Using calibrated equipment, an engineer maps actual light levels across the building and compares them against the recommended illuminances in HSG38. Corridors and walkways require a minimum of 50 lux. Process control rooms are recommended at 300 lux. Engineering drawing work requires up to 750 lux. If a space has changed function since installation, the applicable standard may have changed too.
Lumen depreciation assessment: Using the original installation specification as a baseline, the audit identifies where output has fallen and whether the decline is within expected parameters or indicates an accelerating problem.
Controls verification: Every sensor, timer, dimming zone and daylight-linked control is tested against the original design intent. Deviations are logged and costed in terms of energy impact.
Energy usage validation: Actual consumption data is compared against the projected savings from the original upgrade. If the gap is significant, the audit identifies why.
Emergency lighting check: Emergency lighting must be tested and documented in accordance with BS 5266. If your test records are incomplete or overdue, that’s a compliance exposure that needs addressing regardless of the state of the rest of the system.
A Simple Lighting Check You Can Do In-House
Before commissioning a professional audit, a facilities manager can complete a basic visual check that identifies the most obvious issues.
| Check | What to look for |
| Walk each zone at working hours | Areas that feel noticeably dimmer than adjacent spaces |
| Inspect diffusers and covers | Yellowing, heavy dust deposits or discolouration |
| Check sensor indicators | Any presence or daylight sensors showing fault indicators |
| Review energy monitoring | Monthly kWh data compared to post-install baseline |
| Confirm emergency light test log | Last recorded function test and duration test dates |
| Ask staff | Complaints of glare, flicker, eye strain or insufficient light |
This check takes around an hour for a standard floor plate and will surface the most visible problems. It won’t, however, give you the data you need to make compliance or ROI decisions.
What This DIY Check Won’t Tell You
A visual walkthrough can’t replace calibrated lux measurements, and without those you can’t confirm whether light levels meet the standards in HSG38. It also can’t identify gradual depreciation that hasn’t yet become obvious to occupants — research shows most people don’t notice reduced light levels until output falls to around 70% of the original, which means problems can accumulate well before they generate complaints.
Controls faults, driver wear and emergency lighting compliance all require equipment and documentation to assess properly. If your building is subject to ESOS audits, insurance inspections or BREEAM reviews, a visual check won’t produce the evidence those processes require.
When a Professional Commercial Lighting Audit is Worth It
A professional LED lighting performance audit is the right call in the following situations:
- An ESOS audit is approaching and you need to validate the savings your upgrade was supposed to deliver.
- Your building has changed layout, use or occupancy since the original installation.
- You’ve had staff complaints about light quality that persist despite adjustments.
- You manage multiple sites and need consistent performance data across an estate.
- Your energy bills haven’t tracked down as expected since the LED upgrade.
- Emergency lighting hasn’t been formally tested and documented within the last 12 months.
Any one of these is a sufficient trigger. A commercial LED lighting audit in these circumstances is risk reduction, not discretionary spend.
What You Gain From Optimising an Existing LED System
The business case for a post-install audit isn’t about replacing what you’ve already invested in. In most cases, the audit finds that adjustments — controls reconfiguration, targeted cleaning, sensor recalibration, driver replacement in specific zones — restore performance without significant capital expenditure.
The HSE’s guidance links poor lighting directly to headaches, lethargy, irritability and reduced concentration, and states that it can be a contributory factor in sick building syndrome. Restoring a system to its specified performance addresses those risks without the disruption of a new installation.
For organisations managing capital budgets carefully, audit-led optimisation extends the serviceable life of existing assets — deferring replacement spend while maintaining the energy savings and compliance position the original upgrade was designed to deliver.
Our case study on reducing electricity costs in commercial buildings illustrates how this plays out in practice over a multi-year horizon.
For facilities managers who need to demonstrate LED lighting and compliance performance to senior stakeholders or insurers, a professional audit report also provides the documented evidence that a visual check cannot.
Next Steps: Audit, Adjust, Then Decide
If your LED installation is more than two years old and hasn’t been formally reviewed, the starting point is a professional assessment. It will tell you whether your system is still delivering what it was designed to deliver — and where to focus if it isn’t.
Our commercial LED lighting solutions include post-install performance reviews as well as new system design and installation. If you’re not sure whether your current setup needs attention, an audit is the low-risk way to find out.
Get a quote and we’ll arrange an initial conversation about what a lighting audit would cover for your building.