A commercial fan that runs continuously is a small, permanent line on the electricity bill, and over a ten-year life the running cost often dwarfs what the fan cost to buy. The good news is that it is easy to work out, and easy to cut. This guide shows you the one formula you need, worked examples by fan type at 2026 electricity prices, and the single biggest lever for reducing the bill.
Quick answer: Running cost = fan power (kW) x hours run per day x days per year x electricity price (per kWh). At an indicative commercial rate of 27p/kWh, a 200W fan running 24/7 costs about £473 a year; the same duty on an efficient EC motor drawing 90W costs about £213. The motor type is where the money is. Browse efficient options in commercial extractor fans.
In this guide
The running-cost formula
Every fan running cost comes down to four numbers. Get each one and multiply them together.
| Value | Where to find it |
|---|---|
| Fan power in kilowatts (kW) | On the datasheet, usually quoted in watts. Divide watts by 1,000 to get kW. Use the power at the speed you actually run, not the maximum |
| Hours run per day | Continuous extract is 24. A fan on a time clock or occupancy might be 10 to 14 |
| Days per year | 365 for continuous, or the number of operating days for intermittent duty |
| Electricity price per kWh | From the electricity bill. UK commercial rates in 2026 sit broadly around 25p to 30p per kWh; this guide uses 27p as an indicative figure |
Annual cost = kW x hours/day x days/year x price. Example: a 0.20 kW fan, 24 hours, 365 days, at £0.27 = 0.20 x 24 x 365 x 0.27 = £473 a year.
The important habit is to use the power the fan actually draws at its working speed. A fan rated 400W at full speed may only pull 150W when run at the lower speed a correctly sized system needs, and running cost falls faster than speed because fan power follows roughly the cube of speed.
Worked examples by fan type
Indicative annual running costs at 27p/kWh. Actual figures depend on the specific model, the speed it runs at, and your tariff, so treat these as planning estimates.
| Fan type | Typical power | Run pattern | Indicative annual cost |
|---|---|---|---|
| Small inline duct fan (EC) | 35 W | 24/7 | ~£83 |
| Light commercial inline (AC) | 120 W | 24/7 | ~£284 |
| Commercial box fan | 250 W | 24/7 | ~£591 |
| Cased axial, medium duty | 550 W | 14 hrs, 6 days | ~£432 |
| Roof-mounted kitchen extract | 1.1 kW | 14 hrs, 360 days | ~£1,497 |
| Large industrial extract (3-phase) | 3.0 kW | 24/7 | ~£7,096 |
The pattern is clear: for anything running continuously, the yearly running cost quickly overtakes the purchase price. On the larger units it can exceed the fan price several times over within the first year, which is exactly why motor efficiency matters so much on commercial duty.
The biggest lever: EC motors
The single biggest influence on running cost is the motor type. Older commercial fans use AC (alternating current) induction motors. Modern fans increasingly use EC (electronically commutated) motors, which are brushless DC motors with built-in electronics. EC motors are typically 20 to 40% more efficient than the equivalent AC motor across the operating range, and the gap is widest at part load, which is where most fans actually run.
| Same duty, 24/7 at 27p/kWh | AC motor | EC motor |
|---|---|---|
| Power drawn | 200 W | 90 W |
| Annual running cost | ~£473 | ~£213 |
| Saving per year | ~£260 | |
| Saving over 10 years | ~£2,600 | |
On a fan that runs continuously, an EC motor typically pays back the small price premium within the first year or two and saves money every year after that. If you are specifying a new commercial fan that will run for long hours, an EC motor is almost always the right call on total cost of ownership, even where the upfront price is higher.
Speed and demand control
Because fan power rises with roughly the cube of speed, small reductions in speed produce large reductions in running cost. Dropping a fan to 80% speed cuts airflow by 20% but power by around half. Two practical ways to exploit this:
- Set the fan to the speed the system actually needs. Many commercial fans run flat out because nobody set them down after commissioning. If the design airflow is met at a lower speed, run it there. A fan speed controller makes this straightforward.
- Use demand control. Link the fan to occupancy, CO2, humidity or a time clock so it only runs hard when it needs to. A kitchen extract that boosts during service and trickles otherwise costs a fraction of one that runs at full speed all day.
The cube law is the reason a correctly sized fan on the right speed beats an oversized fan throttled by a damper. Oversizing then choking the airflow wastes energy as pressure drop. Size the fan to the duty and control the speed.
The other levers: sizing, ductwork, maintenance
After motor type and speed control, three things quietly push running costs up:
- Oversizing. A fan bigger than the duty needs runs inefficiently and usually louder. Size to the required airflow and pressure, not to a round-number margin.
- Ductwork resistance. Undersized, over-bent or long flexible duct runs force the fan to work harder for the same airflow, which shows up directly on the bill. Getting the ductwork right is as much an energy decision as a performance one; see our guide to ducting.
- Maintenance. A clogged filter, a dirty impeller or a slipping belt all increase power draw for the same output. Clean filters and impellers on schedule and running cost stays where it should.
When it pays to replace an old fan
If you have an older AC fan running long hours, it is worth doing the sum on replacing it. Work out the current running cost from its power rating, then the running cost of an equivalent EC fan, and compare the annual saving against the purchase and install price.
As a rough guide, a continuously running commercial fan drawing 200W or more on an old AC motor will usually justify replacement with an EC unit on energy savings alone within two to three years, sometimes sooner at higher power. The higher the power and the longer the run hours, the faster the payback. For a fan that runs a few hours a day, the case is weaker and it may be better to wait until it fails.
Related guides
For choosing the fan itself, see our best commercial extractor fans guide and browse the commercial extractor fans range. If you are budgeting a new installation rather than the running cost, see the commercial extractor fan installation cost guide. To control speed and cut the bill, see fan speed controllers.
Frequently asked questions
How much does a commercial extractor fan cost to run?
It depends on the fan's power, how long it runs and your electricity tariff. Using the formula power (kW) x hours x days x price, a 200W fan running continuously at an indicative 27p/kWh costs roughly £473 a year. A small EC inline fan might cost under £100 a year, while a large industrial extractor running 24/7 can run into thousands.
How do I calculate a fan's running cost?
Multiply the fan's power in kilowatts by the hours it runs per day, by the days per year, by the electricity price per kWh. For example, a 0.25 kW fan running 24 hours a day, 365 days a year, at 27p/kWh costs 0.25 x 24 x 365 x 0.27, which is about £591 a year. Use the power at the speed you actually run the fan.
Are EC fans cheaper to run than AC fans?
Yes. EC (electronically commutated) motors are typically 20 to 40% more efficient than equivalent AC induction motors, and the gap is widest at part load where most fans run. On a continuously running commercial fan, an EC motor commonly saves in the region of £200 or more a year and pays back its price premium within the first year or two.
Does running a fan slower save much money?
Yes, more than most people expect. Fan power rises with roughly the cube of speed, so running a fan at 80% speed cuts airflow by about 20% but power by around half. Setting the fan to the speed the system actually needs, using a speed controller or demand control, is one of the cheapest ways to cut running cost.
What electricity price should I use to work out running cost?
Use the unit rate from your own electricity bill for the most accurate figure. As an indicative planning figure, UK commercial electricity in 2026 sits broadly around 25p to 30p per kWh; this guide uses 27p. Prices vary by supplier, contract and consumption, so always check your current rate for a real budget.