VRF HP to TR Converter

A consultant's schedule says "16 HP outdoor unit". The client's brief is written in tons. The electrical drawing wants kilowatts. Three units, one machine, and a conversion factor that's not the same one used for residential split systems — which is exactly where the errors creep in.

Where the 2.8 kW per HP Convention Comes From

VRF sizing in horsepower is a Japanese inheritance. Daikin's VRV line — the system that created the category in 1982 — designated outdoor units by HP, and the rest of the industry followed so that specifications stayed comparable across brands.

The number isn't derived from anything mechanical. It is a product-line convention, and it holds up well against published data:

Consistent to within a fraction of a percent. That's why 2.8 kW/HP works as a planning figure — but for a tender or a load check, always read the rated capacity from the manufacturer's engineering data for the specific model and series, because ratings shift slightly between generations and between 50 Hz and 60 Hz markets.

VRF HP to TR, kW and BTU Table

Planning values across the standard outdoor unit range, including the modular combinations used for larger systems.

VRF HP Is Not the Same as Residential Split HP

This is the single most common source of confusion, and it produces a consistent 6% error if you get it backwards.

Three different quantities wearing the same two letters. A 10 HP VRF unit is about 28 kW; ten residential "1 HP" splits would total about 26.4 kW; and ten mechanical horsepower is 7.46 kW of shaft work, which has nothing to do with cooling at all. For the residential convention see ton to HP and the aircon conversion chart.

Why Indoor HP Does Not Add Up to Outdoor HP

Add up the indoor units on a VRF schedule and the total will usually exceed the outdoor unit rating — often by 10–30%. That's deliberate, not a mistake on the drawing.

The design parameter is connection ratio (also called diversity): total connected indoor capacity ÷ outdoor capacity. Manufacturers typically permit somewhere between about 50% and 130%, and the logic is that rooms don't peak simultaneously. A west-facing office peaks late afternoon; the east side peaked at 10 a.m.; the meeting room only loads when occupied.

• Under 100% — outdoor unit has headroom; every zone can run flat out at once. Used where simultaneous peak is real, such as data or process rooms.
• 100–130% — the normal commercial case. Cheaper plant, relies on genuine diversity in the occupancy pattern.
• Over the manufacturer's limit — not permitted, and in practice means every zone underperforms on the hottest afternoon of the year.

So when you convert HP to tons for a capacity check, be clear which number you're converting: outdoor unit capacity is what the plant can deliver; connected indoor capacity is what the terminals could theoretically demand.

A Note on Heating Capacity

Heat-pump VRF outdoor units are usually rated slightly higher in heating than in cooling at nominal conditions — but that heating figure falls as outdoor temperature drops, and defrost cycles reduce delivered output further. Never size a heating application from the cooling HP figure alone; use the manufacturer's capacity tables at your design outdoor temperature.

Related Tools

For general refrigeration conversions use ton to HP, BTU to HP and HP to ton. Cooling capacity in metric is handled by cooling kW to HP, and for electrical consumption rather than capacity see aircon HP to watts.

For residential split systems rather than commercial VRF plant, AC horsepower uses the 9,000 BTU per HP convention instead.