Phoenix Journal · Extraction
A dashboard nobody reads is just an expensive way to be surprised by the bill. Here is how energy monitoring turns one blunt figure into decisions that actually cut what your kitchen extraction costs to run.
Energy monitoring only saves money when the numbers lead to a decision. A dashboard nobody reads is just a more expensive way of being surprised by the bill.
Most commercial kitchens are metered at a single point - one supply, one figure, one shock at the end of the quarter. That single number tells you how much you spent, but it tells you almost nothing about why. It cannot separate the extraction fan that ran all night from the fryer that was left on, or the walk-in that is icing up from the canopy that is pulling twice the air it needs. Monitoring earns its keep at the moment it turns that one blunt figure into a set of answers you can act on: which piece of plant, at which hour, on which day, and whether that is normal.
The good news is that the potential is real. When kitchens actually act on the insight from monitoring, savings of 10 to 30 per cent of energy use are well within reach - and in extraction specifically, where fans are often the single largest electrical load, the gains can be larger still. The catch is in the word act. This article is about the difference between measuring energy and reducing it, and where the real money hides in a kitchen ventilation system.
A standard supply meter, even a modern half-hourly one, sees your whole site as a single black box. That is fine for the energy supplier and useless for you. If you want to change behaviour or spend sensibly on upgrades, you need to know where the energy is going, and that means sub-metering the loads that matter: the extraction and supply fans, the refrigeration, the cooking line, the lighting and small power.
Sub-metering used to be expensive enough to put people off, but multi-input meters that read many circuits from one unit have brought the cost down by roughly 20 to 50 per cent compared with fitting a separate meter to every circuit. That changes the maths. Once each major load is measured on its own, three things become possible that a single meter can never give you.
None of this requires a huge platform. It requires the right circuits measured, a sensible reporting rhythm, and someone whose job it is to read the report and respond. The technology is the cheap part. The routine around it is what actually saves money.
In a busy kitchen the extraction and make-up air fans frequently run flat out for the entire time the building is open, whether or not anyone is cooking. That is where monitoring pays for itself fastest, because fan power follows the fan affinity laws - it scales with the cube of speed. Slow a fan to half speed and it draws roughly one eighth of the power. Run it at 40 per cent and it uses only about 6 per cent of what it consumes at full tilt. This is not a marginal saving; it is the single biggest lever in the whole system, and monitoring is how you find out you are pulling it far too rarely.
This is the logic behind demand controlled kitchen ventilation, where temperature and optic sensors in the canopy ramp the fans up when the line is hot and busy and ease them back when it is not. Systems of this kind routinely cut fan energy by more than 50 per cent, and in the right kitchen the reduction can approach 80 per cent. But you do not need to buy new controls to benefit - simply seeing, on a chart, that your fans ran at 100 per cent for four hours before the first order landed is often enough to justify a timer change that costs nothing.
The figures that matter
Three numbers explain why extraction is the first place to point your monitoring, and why keeping the system clean is part of the same conversation.
Read together these tell a simple story. Fans are the dominant load, small changes in how they run produce large changes in cost, and the whole thing only works if someone is watching the data and responding to it.
Here is the part that gets missed. A rising energy figure on your extraction circuit is very often not a control problem at all - it is a cleaning problem. As grease-laden baffle filters and ductwork foul up, back pressure climbs, and the fan has to work harder to move the same volume of air. A clean baffle offers steady resistance and lets a constant airflow through at the lowest energy cost; a clogged one forces the motor to draw more current every week to fight its way past the blockage. Left alone, that same grease is also the reason kitchen extract systems catch fire.
This is why the smartest operators treat their monitoring data and their cleaning schedule as one system. The current drawn by the extraction fan, trended over weeks, is effectively a live readout of how dirty the system is getting. A gentle upward creep between cleans is exactly what you would expect; a steep climb tells you the interval is too long, the filters are past their best, or something downstream is restricting the flow. Cleaning to the recognised standard - the BESA TR19 Grease specification that insurers and environmental health officers look for - keeps the system safe and, as a direct consequence, keeps it running at the airflow and the power draw it was designed for. Efficiency and compliance turn out to be the same housekeeping.
There is a seasonal dimension worth understanding too, because extraction interacts with the rest of the building. Every cubic metre of air you throw out of the canopy has to be replaced, and in warm weather that replacement air may be conditioned, so an over-driven fan quietly inflates your cooling bill as well as its own. If you have ever wondered why your energy bill climbs in summer, the extraction system pulling too hard is frequently part of the answer. Monitoring lets you see that interaction instead of guessing at it, and it dovetails with a broader look at where a commercial kitchen loses energy in the first place.
For larger operators there is a compliance backdrop as well. Under the Energy Savings Opportunity Scheme, organisations that count as a large undertaking - broadly 250 or more staff, or turnover above £44 million with a balance sheet total above £38 million - must audit at least 95 per cent of their total energy use, and under the current phase they were due to file an action plan by March 2025 and a first progress update by December 2025. Good sub-metering makes that reporting straightforward instead of a scramble, because you already hold the evidence. Even if you sit well below those thresholds, the same discipline - measure the big loads, trend them, act on the drift - is what turns monitoring from a cost into a saving.
Questions
No - monitoring measures, it does not save. The savings come from acting on what it shows you, whether that is changing a fan timer, scheduling a clean or replacing a control. Kitchens that respond to their data typically cut energy use by 10 to 30 per cent, while those that install a dashboard and ignore it save nothing. Treat the report as a to-do list, not a wallchart.
Start with the extraction and make-up air fans, because they are usually the largest and most over-run electrical load and follow the cube law, so small changes in how they run produce large changes in cost. Refrigeration is the sensible second, as it runs around the clock and readily flags faults. Cooking line, lighting and small power can follow once the big two are covered. Multi-input meters let you read several of these circuits from one unit at lower cost.
As a slow, steady rise in the current drawn by the extraction fan between cleans. Grease building up on filters and duct walls increases back pressure, so the fan works harder to move the same volume of air and draws more power week on week. A gentle creep is normal; a steep climb means your cleaning interval is too long or the filters are spent. Cleaning to the BESA TR19 Grease standard restores the designed airflow and the lower power draw.
Only if your organisation is a large undertaking - broadly 250 or more employees, or a turnover above £44 million together with a balance sheet total above £38 million. Those in scope must audit at least 95 per cent of their total energy use and file action plans and progress updates on the scheme's timetable. If you sit below the thresholds ESOS does not compel you, but the same habit of metering your big loads and acting on the trend still saves money.
Phoenix Duct Clean · by the numbers
The right kit only helps if the system stays clean. Phoenix degreases canopies, filters and ductwork to TR19 Grease - UK-wide, overnight.