A heat-recovery unit's heat recovery percentage often becomes the main comparison figure. However, it is not the same as an equivalent reduction in the whole house's heating bill. The percentage describes heat transfer assessed under specific conditions, while many additional factors determine the annual result. Air volumes, operating times, climate, electricity and heating-source data are needed. Without clear assumptions, a precise promise of euro savings may be misleading.
What the system actually recovers
The DOE ventilation overview explains that a heat-recovery system reduces the energy losses associated with air exchange. It does not eliminate every building heat loss. Walls, windows, the roof and other parts of the building remain separate heat-transfer paths. You therefore cannot simply apply the catalogue percentage to the house's entire annual bill.
The comparison baseline matters too. An adequately ventilated house without heat recovery and an inadequately ventilated house do not perform the same function. If air is barely replaced in one case, lower consumption does not mean equivalent comfort or air exchange. The comparison must use the same justified task.
The rating has test conditions
The heat-transfer efficiency in a catalogue may have been assessed at a particular airflow and under other specified conditions. You need to know exactly what the stated figure means and which method produced it. The highest percentage cannot automatically be treated as the annual average. Data for different models must be comparable in the same sense.
The Komfovent installation manual shows the variety of designs and additional components. The unit's configuration matters for actual operation, but a schematic alone does not reveal annual benefit. You need technical data for the specific model and assumptions about use at the property, not a general impression of the manufacturer or heat-exchanger type.
Air volume and time change the result
A higher planned airflow means a different ventilation energy task. The number of hours spent in different modes matters too. If maximum airflow is needed only briefly, it cannot be applied to the entire day. Conversely, a minimum-mode figure alone does not describe the use of a house with more permanent occupants.
Write down the comparison assumptions. State the airflows planned for normal and boost operation, whether there is a weekly schedule and when the house is unoccupied. If actual data is not yet available, this is an indicative forecast. It must not be renamed measured annual savings simply because a calculator returns many decimal places.
Electricity remains part of the overall balance
Fans use electrical energy, and additional heating may operate in some modes. The Komfovent C6M user manual describes specific control functions. When assessing benefit, understand what the data shows and which components are included. A heat recovery percentage alone does not eliminate electricity use.
The monetary value of a kilowatt-hour of heat may also differ from that of electricity. If heating uses a heat pump, recovered heat is not simply the same quantity of electricity saved. Assumptions about the heating source's operation and prices are needed. This article gives no universal tariff or payback period because these differ between properties.
Illustrative example: two houses with the same floor area
Suppose two houses of similar size have the same unit. One has more occupants and uses boost mode more often, while the other is empty for part of the time. Even with the same heat exchanger, annual air volume and electricity use may differ. Floor area and a catalogue percentage alone are therefore insufficient for a reliable euro comparison.
Assessing actual benefit after a year requires consistent data and a comparison method. Different winters, heating settings and the effects of other work must be taken into account. A lower overall household bill alone does not prove that the heat-recovery unit created the entire difference. The roof may have been insulated at the same time, or the occupants' lifestyle may have changed.
Installation determines whether the assumptions hold
Leaking ducts, incorrect balance and inadequate insulation can change the actual result. Selecting a model must therefore be followed by proper system installation and airflow checks. A catalogue rating does not guarantee the contractor's workmanship. Assess it alongside the actual layout and acceptance data.
The condition of filters and maintenance matter too. You cannot compare a well-maintained system with another whose components have long been neglected and attribute the entire difference to the model. If consumption or comfort changes, check operating conditions first. Only then decide whether equipment adjustment, repair or an upgrade is needed.
Payback is not the only criterion
Owners may also value consistent air supply, filtration, noise control and convenience. There is no need to artificially convert these benefits into guaranteed euros. It is better to identify them separately. It then becomes clear what result is being paid for and which aspects are based on measurement or relate to usage preferences.
At the same time, do not ignore running costs. Filters, maintenance and possible repairs belong in a long-term budget. A sound purchase decision considers the whole system and its scope. The highest percentage may be a useful indicator, but it should not replace every other question on its own.
A real comparison must respect its limitations
If heat-recovery ventilation is installed at the same time as windows are replaced, the total bill alone cannot precisely separate the effect of each job. That would require an appropriately selected assessment method and additional data. A report should clearly state what could not be established rather than attribute the entire difference to one product. This also applies to an unfavourable result: a higher bill may reflect a colder year or different use, not just a characteristic of the unit.
How to request a sound calculation
Ask for airflows, time periods, climate and heating-source assumptions, the electricity component and the tariffs used, with their dates. It must be clear what was calculated and what was actually measured. Read more about selection here. In your enquiry, add the model and the data available. An honest assessment will show not only the potential benefit but also the limits of its uncertainty.
Information sources
You can read the explanation without leaving this page. The original document opens only when you choose its link.