3 HP and 3.5 HP Air Conditioners: Who They Suit and What to Check in Your Electrics

A 3 HP AC suits a space of about ⁦36–41⁩ m² on a mid-level floor, and a 3.5 HP AC a space of about ⁦40–46⁩ m². On a sunny top floor, the ranges shrink by about 20%.

The calculation, at about ⁦650 BTU⁩ per m² (the basis of the calculator on our site):

• 3 HP (about ⁦27,000 BTU⁩): about 41 m² on a mid-level floor, about 38 m² when the living room is open to the kitchen, about 36 m² on a top floor and about 33 m² on a top floor with sun exposure.
• 3.5 HP (about ⁦29,000–⁦30,000 BTU⁩⁩): about 46 m² on a mid-level floor, about 42 m² when the living room is open to the kitchen, about 40 m² on a top floor and about 37 m² on a sunny top floor.
• Ceiling above 2.8 m: subtract another 10% or so.

Typical cases: a living room, dining area and open kitchen in a 5-room apartment, ⁦38–45⁩ m² in total. A penthouse with a ⁦30–35⁩ m² living room. The ground floor of a private house. A large home office or clinic.

For a space of about ⁦30–34⁩ m², a 2.5 HP AC is better: it’s cheaper and doesn’t need a 20-amp breaker. The full table, up to 5 HP, and the calculator are in our guide on how many horsepower an AC needs.

The following examples are calculated at about ⁦650 BTU⁩ per m² with the additions used by the calculator on our site. They’re illustrative, not a substitute for an installer’s measurement.

• 26 m² living room and 10 m² open kitchen, third floor of six: 36 m² × 650 = ⁦23,400 BTU⁩, plus 10% for an open space, about ⁦25,700 BTU⁩. An AC of about ⁦27,000 BTU⁩ fits, or a 2.5 HP model with an upper range of ⁦25,000 BTU⁩ or more.
• The same space on the top floor: ⁦23,400 BTU⁩ plus 25% for the open space and roof, about ⁦29,300 BTU⁩. A 3.5 HP AC fits, such as the Tadiran Air One INV 370 or Electra A Inverter 390.
• 42 m² living and dining area in a penthouse with west-facing windows: ⁦27,300 BTU⁩ plus 25%, about ⁦34,000 BTU⁩. That’s beyond a 3.5 HP wall unit. A 4 HP AC, two units, or a mini-central AC fits.
• Ground floor of a private house, 38 m², 3 m ceiling: ⁦24,700 BTU⁩ plus 10% for the ceiling, about ⁦27,200 BTU⁩. A 3 HP AC fits.

In every case, if the space is long, check with the installer where the unit will be installed and where it will blow the air.

Stores have almost no models labeled exactly 3 HP. Most importers jump from about ⁦24,000 BTU⁩, labeled 2.5 HP, to about ⁦29,000 BTU⁩, labeled 3.5 HP.

Examples from the store pages we checked:

• Tadiran Air One INV 340: ⁦23,750 BTU⁩, labeled 2.5 HP. Air One INV 370: ⁦29,100 BTU⁩, labeled 3.5 HP. There’s no model in between.
• Electra A Inverter 340: ⁦24,260 BTU⁩, labeled 2.5 HP. A Inverter 390: ⁦29,000 BTU⁩, labeled 3.5 HP.
• Haier Pro X Inverter 32/3P: ⁦27,153 BTU⁩, i.e. exactly 3 HP, but the store labels it 3.5 HP.

So if your calculation comes out at about ⁦27,000 BTU⁩, you can choose between two options. The first is a model of about ⁦29,000 BTU⁩, with reserve for heat-wave (sharav) days. An inverter AC running below its full capacity doesn’t waste electricity, because the compressor scales down. The second is a model of about ⁦24,000 BTU⁩ with a wide upper range, which suits a space close to 36 m² that isn’t on a top floor.

Either way, don’t trust the label. Compare the cooling output line in BTU/h on the spec sheet.

Single-phase 3.5 HP models need a 20-amp breaker and a dedicated line. Some models of this size are three-phase, and those can only be connected in a home with a three-phase connection.

What the spec sheets we checked say:

• Tadiran Air One INV 370: 230V single-phase, 20C fuse, current of 12.2 amps in cooling (up to 14 amps) and 11.9 amps in heating (up to 15.5 amps).
• Electra A Inverter 390: single-phase, 1X20A type C breaker, current of 12 amps in cooling and 10 amps in heating.
• Haier Pro X Inverter 32/3P: three-phase per the store page.
• The store’s list also includes models like the Tadiran Galaxy 36 3P and Galaxy 36 INV, at the same output in a three-phase and a single-phase version.

What to check before buying:

• What connection your home has. The Israel Electric Corporation bill or the main panel shows whether the connection is single-phase or three-phase.
• Whether the cable suits 20 amps. A larger breaker on a thin cable is a hazard. Only a licensed electrician can approve the change.
• The total load. A 3.5 HP AC, an induction cooktop and an electric water heater (dud) running together can trip the main breaker on a small single-phase connection.

Per Tadiran, adding a dedicated outlet costs about ₪⁦300–1,000.⁩ Switching to a three-phase connection requires an application to the Electric Corporation and panel work, so in a home with a single-phase connection it’s better to choose a single-phase model.

In an open, square space of up to about 45 m², one ⁦3–3.5⁩ HP wall unit is the cheap solution. In a long or L-shaped space, or above 45 m², two units or a mini-central AC will work better.

Comparison based on the prices we saw:

• One 3.5 HP wall unit: about ₪⁦3,900–5,100⁩ for the AC, plus about ₪⁦1,200–1,800⁩ for installation per pro.co.il (an Israeli contractors’ site). About ₪⁦5,100–6,900⁩ in total.
• Two ⁦1.5–2⁩ HP ACs: about ₪⁦3,700–6,800⁩ for the ACs, plus two installations. About ₪⁦5,700–9,800⁩ in total, but distribution is better, and you can run just one unit.
• Mini-central AC: per pro.co.il, installing a ⁦3.5–7⁩ HP mini-central costs about ₪⁦4,000–5,500,⁩ and a full project with ducts, a dropped ceiling and diffusers in a 130 m² apartment costs about ₪⁦15,000–20,000.⁩

A large wall unit works when the indoor unit can throw air along the length of the space. If there’s a column, partial wall or corner between the living room and kitchen, the air won’t reach. If you’re renovating and planning AC for the whole apartment, a mini-central AC almost always pays off better than several large wall units.

Usually about ₪⁦5,100–6,900⁩: about ₪⁦3,900–5,100⁩ for the AC plus about ₪⁦1,200–1,800⁩ for standard installation, before extras.

With ACs of this size, extras are more common:

• Piping: about ₪150 per meter beyond what’s included, per pro.co.il, for ACs above 2 HP. Tadiran gives a range of ₪⁦100–200⁩ per meter.
• Crane: a 3.5 HP outdoor unit is heavy. A crane costs about ₪250 per hour, and carrying without an elevator about ₪200 per floor, per pro.co.il.
• Dedicated electrical line: about ₪⁦300–1,000⁩ per Tadiran, and more if the cable needs replacing.
• Bracket or base for the outdoor unit: in a penthouse, the unit often sits on the roof or a base. Ask the installer whether it’s included.

Ask for a written quote itemizing all the line items, and ask whether the installation is done by an importer-authorized installer. Per Tadiran, the installation warranty comes from the installer and is separate from the AC’s warranty. The full price list is in our AC installation cost guide.