MVHR running costs and savings

How much does MVHR cost to run?

MVHR uses electricity to run its fans continuously. A well designed domestic system typically uses around 250 to 500 kilowatt hours of electricity a year, which at the mid-2026 price cap of about 26 pence per kilowatt hour is roughly £65 to £130 a year. A poorly designed system with restrictive ducting can use considerably more.

Because the fans run all the time, the running cost is steady rather than seasonal. The single biggest factor in it is the specific fan power of the unit and the resistance of the ducting: a low fan power unit in well designed ducting sits at the bottom of that range, while a high resistance system pushes it up. Use your own electricity unit rate to get a figure for your home.

Sources: Ofgem

How much electricity does an MVHR unit use?

The fans in a domestic MVHR unit typically draw somewhere between about 30 and 90 watts running continuously, depending on the unit and how well the ducting is designed. Running non-stop, 40 watts adds up to roughly 350 kilowatt hours a year. Boost periods, when extraction increases, add a little more. The key number to compare is specific fan power.

That is a similar continuous draw to a couple of low-energy light bulbs left on, spread across the whole year. Our running cost calculator turns the fan power and your electricity price into an annual figure, so you can see what a specific unit would cost in your home.

Does MVHR save money on heating?

MVHR recovers most of the heat from the air it extracts and returns it to the incoming fresh air, so less heat is lost through ventilation and the heating has less to make up. The saving is real but depends heavily on how airtight the home is. In an airtight home it is worthwhile; in a leaky one, uncontrolled draughts undo much of the benefit. It reduces heating demand rather than replacing the heating.

It is best to think of the heat recovery as reducing a cost you would otherwise pay, not as generating a saving on its own. The electricity to run the fans is a real, if modest, cost; the recovered heat offsets part of your heating. In a well insulated, airtight home the balance is favourable, which is the whole point of using MVHR there.

What is specific fan power and why does it matter for running cost?

Specific fan power, or SFP, measures how much electricity the fans use to move a given amount of air, in watts per litre per second. A lower SFP means a more efficient system that costs less to run. Because MVHR runs continuously, a low SFP unit in well designed ducting can cost noticeably less over a year than a high SFP one moving the same air.

SFP sits alongside heat recovery efficiency as the two numbers worth comparing on a unit. Efficiency tells you how much heat it keeps; SFP tells you how much electricity it burns doing so. A unit can score well on one and poorly on the other, so look at both when choosing.

Is MVHR expensive to run?

No, running cost is one of the strengths of MVHR. The continuous electricity use is modest, usually well below the value of the heat it helps retain in an airtight home. The bigger cost is the installation, not the running. Choosing a low specific fan power unit and a well designed duct layout keeps the ongoing cost at the low end of the range.

People sometimes worry that a system running all the time must be expensive, but the fans are low powered and efficient. The number to watch when buying is specific fan power, because a poorly designed high resistance system is where running costs actually climb.