Phoenix Journal · Extraction
When the outside temperature rises, a commercial kitchen quietly becomes more expensive to run. Much of that extra cost traces back to your extraction system and the cooling it forces the building to do.
The summer puzzle
It is a bright morning in July, the service has not even started, and the kitchen is already warm.
By mid-afternoon the chefs are working in a heat that no amount of open doors seems to shift. The air conditioning in the front of house is running flat out, the extract canopy is roaring away above the ranges, and somewhere in the plant room a fan that has not been looked at in eighteen months is grinding through the day. Then the electricity bill arrives, and it is noticeably higher than the one you paid in February - even though the heating is off and the days are longer and brighter.
It feels backwards. Surely a warmer month should cost less to run, not more. The heating is idle, after all. But a commercial kitchen does not behave like a home. In summer, the very systems that keep the space workable - your extraction, your make-up air and your cooling - all lean on each other, and when one of them is struggling the others quietly pick up the slack. That is where the summer premium hides, and a good deal of it is within your control.
The instinct is to blame the tariff, or the weather, or simply write it off as the cost of a busy season. Those things play a part. But the largest movable chunk of a summer bill in a catering environment usually comes from two linked places: the amount of heat your kitchen is throwing into the building, and the amount of energy it takes to move air in and out of the space against that heat.
Every cubic metre of air your canopy pulls out of the kitchen has to be replaced. That is not optional - it is basic physics, often summed up as air in equals air out. In winter, the replacement air arriving from outside is cool, so it does some of the cooling work for you almost for free. In summer, that same incoming air might be arriving at 25°C or more, and it lands in a room already loaded with heat from fryers, chargrills, ovens and combi steamers.
Your cooling then has to drag all of that air back down to a workable temperature. The sensible cooling load rises directly with the gap between the outside temperature and the temperature you are trying to hold indoors, so a hotter day is not a small increase - it is a compounding one. In most commercial kitchens, the cooking equipment and the make-up air needed to balance the extract together dominate the entire cooling demand of the building. When people say the kitchen is dragging the whole site's energy use up in summer, this is usually why.
Here is the part that catches operators out. An extraction system does not fail all at once. It degrades slowly, over months of service, as grease vapour condenses onto filters, canopy plenums, ductwork and fan blades. As that layer thickens, the same fan has to work harder to move the same volume of air - and a fan that is working harder is drawing more electricity, every single hour it runs.
Industry guidance is blunt on this: grease deposits slow the fan and force it to consume more energy than a clean one, and simply keeping filters and hoods clean can restore up to half of a system's lost efficiency. In summer, when your extract is likely running longer and harder to fight the heat, that hidden inefficiency is amplified. You are effectively paying a surcharge on every hour of extraction, and it never appears as a separate line on the bill - it just makes the whole number bigger.
None of this means you are stuck paying the premium. A well-maintained, clean extraction system is genuinely cheaper to run than a neglected one, and the savings are largest exactly when you feel the heat most. If you want to understand where the money is going before you act, it helps to be able to read a commercial energy bill and find the waste - but the physical fix nearly always starts at the canopy and the ductwork.
Think of your extract fan the way you would think of a person breathing. Breathing through a clean, open airway is effortless. Breathing through a blocked one takes real effort, and you tire quickly. A fan choked with grease is in that second state permanently - and it is you, not the fan, who pays the electricity bill for that effort.
When the canopy, filters, plenum and duct run are properly clean, air moves through the system with far less resistance. The motor settles to a lower, steadier draw. The kitchen clears heat and cooking vapour more effectively, which in turn eases the load on your cooling because the space is not fighting a backlog of hot, humid air. It is a virtuous circle, and it runs in reverse the moment the system is left dirty. This is also the point at which the age and type of your fan motor matters - if you are still running older AC motors, a clean system plus a move to modern EC motors can compound into a meaningful reduction in summer electricity use.
There is an important difference between wiping the filters and actually cleaning the system. The recognised UK benchmark is TR19 Grease, the standalone fire risk management specification published by the Building Engineering Services Association in 2019. It covers the whole route from canopy to discharge point - filters, plenums, horizontal and vertical duct runs, the fan and motor, access panels and the external outlet - because grease travels well beyond the filters and settles everywhere air flows.
The standard is measurable, not a matter of opinion. Deposits are assessed by a Deposit Thickness Test, and the system is expected to be held below a mean of 200 microns of grease, with any single reading above 500 microns triggering immediate localised cleaning. After a clean, a compliant contractor should be able to verify levels below 50 microns. A heavy-use kitchen running 12 to 16 hours a day typically needs this done roughly every three months. Meeting that standard is first and foremost a fire safety requirement - but the same clean, low-resistance system that keeps your insurance valid is also the one that runs most cheaply through a hot summer.
So when the summer bill lands and it is bigger than it feels it should be, resist the urge to file it under bad luck. A good part of that number is telling you something practical: your kitchen is working harder than it needs to in order to move and cool its own air. Clean the extract system properly, keep it clean to a standard, and you take back the most controllable slice of your seasonal running cost - while making the kitchen a far more bearable place to work through the hottest weeks of the year.
Questions
A commercial kitchen does not behave like a home. In summer, the fresh make-up air replacing everything your canopy extracts arrives warm, and your cooling has to condition all of it while the space is already loaded with heat from cooking equipment. The sensible cooling load rises directly with the gap between outdoor and indoor temperature, so hotter days cost disproportionately more. Longer summer service hours then multiply the effect across more running time.
Yes. Grease buildup on filters, ductwork and fan blades increases resistance, so the fan draws more current to move the same volume of air, and it does this every hour it runs. Industry guidance notes that keeping the system clean can restore up to half of its lost efficiency. Cleaning the full route to the TR19 Grease standard lets the fan run at a lower, steadier draw and helps the kitchen clear heat faster, which also eases the load on your cooling.
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.