How much does heat recovery VRF save per year?

Heat recovery VRF is a type of VRF that can cool some spaces while heating others on the same system, and transfers heat drawn from the cooled spaces to the heated ones. A classic heat pump VRF, on the other hand, either only heats or only cools at any one time. The difference can translate into serious energy savings in buildings with simultaneous demand.

How much will be saved cannot be stated with a single number. In this article we explain where the savings come from, in which buildings they are meaningful and by how much, and how the calculation should be done.

How does heat recovery VRF work?

Heat recovery VRF generally uses a three-pipe line, or a two-pipe line with special distribution boxes, between the outdoor unit and the indoor units. These selector boxes, which go by different names depending on the brand, determine whether each indoor unit will cool or heat and direct the refrigerant accordingly.

An indoor unit that is cooling releases the heat it draws from the space into the refrigerant. In a normal system, this heat is rejected to the air at the outdoor unit. In a heat recovery system, this hot gas is sent to another indoor unit that needs heating. The same energy is thus used twice: one space is cooled and the other is heated.

Meanwhile, the outdoor unit acts as a balancer. If the cooling load exceeds the heating load, it rejects the surplus heat to the air; if the heating load is greater, it draws the missing heat from the outdoor air. The closer the loads are to each other, the less work the outdoor unit has to do.

Where do the savings come from?

The source of the savings is that the outdoor unit does less work. When cooling and heating loads balance each other, the outdoor unit does not have to reject heat to the air or draw heat from it; the compressor works largely to move refrigerant between the spaces. As this balance is approached, the overall efficiency of the system rises noticeably.

Manufacturers state that in balanced simultaneous operation, the overall efficiency, that is, the ratio of the sum of cooling and heating capacity to electricity consumption, reaches much higher values than in single-mode operation. The actual savings depend on how long this balance is achieved during the year.

Heat recovery only works if there are spaces that want heating and cooling at the same time. On a summer afternoon when the whole building wants cooling, heat recovery VRF behaves like an ordinary heat pump VRF.

In which buildings does it really save?

Heat recovery VRF provides meaningful savings in buildings that have simultaneous heating and cooling demand for a significant part of the year. This demand usually arises from facade orientation, internal loads, and differences in use.

• Office buildings: Even in winter, interior zones, meeting rooms, and server rooms want cooling while the north facade wants heating.
• Hotels: Rooms are set differently depending on the guest; in spring and autumn, one room can be heating while the one next to it is cooling.
• Hospitals and clinics: Imaging, laboratory, and equipment-heavy areas may want cooling all year round.
• Shops and restaurants: Kitchens and areas with heavy lighting want cooling while entrances and seating areas want heating.

By contrast, in buildings with one-directional, uniform use, for example a single-volume warehouse or a small home, the payback on the additional investment may be weak.

How much is saved per year?

Annual savings vary with the building's simultaneous load profile and can only be calculated reliably with an hourly load analysis. In suitable buildings, ranges such as a 10 to 30 percent reduction in annual energy consumption compared with heat pump VRF are reported; very suitable buildings see higher results and unsuitable ones see negligible results.

The following data are needed for a reliable calculation:

1. Hourly cooling and heating load for each space or zone.
2. The number of hours in the year with simultaneous heating and cooling.
3. The ratio between heating and cooling loads during those hours.
4. The partial-load and simultaneous-operation efficiencies of the selected equipment.
5. The electricity tariff and the building's operating hours.

For example, in an office where the interior zones and server room want cooling constantly in winter, if the facade offices want heating at the same hours, the recovered heat is deducted directly from heating energy. In the same building, in spring and autumn this situation may last for most of the day. The savings come from the sum of these hours. The payback period is determined after the site survey and load analysis.

What should you watch for in the additional investment and design?

Heat recovery VRF requires more equipment and more complex piping than heat pump VRF. Distribution boxes, additional piping, additional weld points, and more detailed commissioning raise the initial investment. How many years it takes for this difference to pay back must be calculated specifically for the building.

The commissioning stage is at least as important as the design. The correct refrigerant charge for the pipe lengths, correct addressing of each distribution box, and testing of the mode changeovers one by one are required. A system that is incorrectly charged or wrongly addressed cannot deliver on site the savings promised on paper. For this reason, keeping the commissioning report and first-year operating data creates a valuable reference for comparing performance in later years.

The most critical point in design is zoning. Indoor units connected to the same distribution box outlet operate in the same mode. If the north and south facades and the interior and perimeter zones are not grouped correctly, the system misses the recovery opportunity. Placing the distribution boxes in accessible locations for maintenance is a great convenience later during faults and refrigerant leak detection.

VRF or another solution?

Simultaneous heating and cooling demand is not met by VRF alone; a 4-pipe fan coil system and a heat recovery chiller serve the same purpose. In large, centralized buildings these options may be more suitable. We covered which system suits your building in detail in our article VRF vs. chiller comparison.

At YOİ Mühendislik we provide site survey, zoning recommendations, installation, commissioning, and maintenance for heat recovery VRF systems. We can read the operating data of your existing system and report its recovery performance. For details, see our VRF service page.

Detailed guide: VRF air conditioner maintenance: intervals, checklist, and maintenance form