Altech ATP-035S12 3.5 kW
(2 reviews)
The Altech ATP-035S12 portable air conditioner: 3.5 kW of cooling power at a tight price, automatic condensate evaporation and a 2-year compressor warranty.
Key features
- Power: 3.5 kW (12,000 BTU/h)
- Energy class: A, R290 gas
- Noise level: Up to 65 dB(A) at top speed
- 2-year compressor warranty included, unusual at this price point
In detail: Altech ATP-035S12, cooling-only monobloc portable air conditioner 12000 BTU
Sold through professional building trade merchants of the Saint-Gobain group (Point.P, Cedeo, Soluclim...) in its home market, the Altech ATP-035S12 is a cooling-only monobloc portable air conditioner that bets on a tight price rather than connected gadgets. Its 3.5 kW (12,000 BTU/h) cooling capacity puts it among the stronger units in the portable category, enough on paper for a well-insulated room up to 35 m².
The unit stays deliberately simple: no app, no WiFi, control runs through an infrared remote and a panel on the unit itself. Three functions are offered, cooling, ventilation and dehumidifying, with a 370 m³/h airflow and a 1.2 L/h dehumidifying capacity. The automatic condensate evaporation system normally does away with emptying a tank, a genuine everyday convenience.
On the spec sheet, the ATP-035S12 runs on R290 gas, a refrigerant kinder to the environment than earlier generations, for an Energy Class A rating and an EER of 2.6. The installation kit (exhaust hose and window vent panel) is supplied, along with an infrared remote control. At 35.5 kg and 46.7 x 76.5 x 39.7 cm, the unit sits in the middle of its category for being wheeled from room to room.
The main strength of this budget model is its manufacturer warranty: 2 years on parts and 2 years on the compressor, a commitment rarely seen at this price point, where most competitors stop at one year. In exchange, noise climbs to 65 dB(A) at top speed (lower speeds aren't disclosed by the manufacturer), and several user reports flag, as with most entry-level monobloc units, an exhaust hose that heats up and slightly warms the room if it isn't properly sealed against the window.
For occasional use in a rental, as a backup for a living room or office, or for a tight budget against connected models at £600 and above, the Altech ATP-035S12 remains an honest option, provided you accept its acoustic comfort limits and its lack of a heating function.
Technical data
Detailed characteristics
Performance
| Type?General technical category the unit belongs to (portable, split, evaporative...). | Monobloc portable, cooling only, with exhaust hose |
|---|---|
| Cooling capacity?The unit's cooling power, expressed in kW or BTU/h (British Thermal Unit per hour). | 3.5 kW (12,000 BTU/h) |
| Energy class?European energy efficiency class (from A+++ to G), showing how the unit's consumption compares with similar models. | A (cooling) |
| Power draw?Electrical power drawn by the unit while running, expressed in watts (W). | 1.35 kW |
| Airflow?Volume of air moved by the unit each hour, in m³/h: the higher it is, the faster the room's air is refreshed. | 370 m³/h |
| Dehumidifying?Amount of water removed from the air by the unit, usually expressed in litres per 24 hours. | 1.2 L/h, automatic condensate evaporation |
| Refrigerant?Gas used in the cooling circuit. R290 and R32 are now favoured for their lower environmental impact. | R290 (eco-friendly) |
| Noise level?Noise emitted by the unit, in decibels (dB(A)). As a reference, a normal conversation is around 60 dB(A). | Up to 65 dB(A) at 1 m at top speed (lower speeds not disclosed by the manufacturer) |
| Recommended room size?Room size or volume the unit is designed for, according to the manufacturer. | Up to 35 m² |
Features and connectivity
| Functions?Operating modes offered by the unit (cooling, fan, dehumidifying, heating...). | Cooling, ventilation, dehumidifying, night mode, timer, auto restart |
|---|---|
| Included accessories?Items supplied with the unit (window kit, remote control, hose...), in addition to the unit itself. | Window kit (exhaust hose and vent panel), infrared remote control |
Dimensions and power supply
| Power supply?Electrical voltage and frequency required to run the unit. | 230V single-phase |
|---|---|
| Dimensions?Width, depth and height of the unit (W x D x H). | 46.7 x 76.5 x 39.7 cm (W x H x D) |
| Weight?The unit's weight, an important factor for a portable air conditioner regularly moved between rooms. | 35.5 kg |
Additional information
| EER | 2.6 |
|---|---|
| Manufacturer warranty?Period during which the manufacturer commits to repairing or replacing the unit in case of failure, excluding damage or misuse. | 2 years on parts and compressor |
Comparison
Around the £430 to £500 mark, the Altech ATP-035S12 naturally compares to the Klarstein Kraftwerk Smart 10K, a connected portable air conditioner sold at a very similar price. Here is how the two compare, based on the public specifications of both manufacturers.
| Criterion | Altech ATP-035S12 | Klarstein Kraftwerk Smart 10K |
|---|---|---|
| Cooling capacity | 3.5 kW (12,000 BTU/h) | 2.9 kW (10,000 BTU) |
| Airflow | 370 m³/h | 440 m³/h |
| Connectivity | Infrared remote only | WiFi, Klarstein app, Alexa, Google Home |
| Noise level | Up to 65 dB(A) | 48 to 65 dB(A) |
| Warranty | 2 years on parts and compressor | Standard manufacturer terms |
| Price observed | ≈€499 | ≈€514 |
In short, the Altech ATP-035S12 offers higher cooling capacity and a longer compressor warranty, while the Klarstein bets on connected control and a more generous airflow. The choice mostly comes down to how much weight you put on WiFi control versus raw power and warranty cover.
Our tester's verdict: Christophe Delpuech
I ran this one for about ten days in a 22 m² south-facing office. Getting started is instant: no app to set up, just the remote and a standard temperature dial. At full power, the room dropped from 29°C to 22°C in a little under 40 minutes, in line with the advertised 3.5 kW. Automatic condensate evaporation held up throughout the test, no tank to empty. What bothered me most was the heat given off by the exhaust hose: poorly insulated out of the box against the window vent panel, it noticeably warmed the air near the opening, and I had to add a strip of foam to cut that down. Noise at top speed is also noticeable, hard to work right next to it without raising your voice. For a living space used during the day, or for occasional stopgap use, the ATP-035S12 gets the job done at a contained price, with a genuine plus: its 2-year compressor warranty, reassuring on an entry-level unit.
Frequently asked questions: Altech ATP-035S12, cooling-only monobloc portable air conditioner 12000 BTU
As with any monobloc air conditioner, some of the extracted heat passes through the hose before being vented outside: if the window seal is imperfect, slight local warming is possible. Properly insulating the hose and vent panel noticeably reduces this effect.
The manufacturer recommends up to 35 m², provided the room is properly insulated and not in direct sun all day. For a poorly insulated room, it's safer to aim for a smaller area.
No, this model is cooling only (ventilation and dehumidifying included, but no heating function). For a reversible unit, you'd need to look at a fixed split air conditioner instead.
Under normal use, no: the unit automatically evaporates most of the condensate produced while running. Only intensive use in a very humid room might occasionally require draining.
This model isn't listed on the big general marketplaces: it's sold through professional building trade merchants of the Saint-Gobain group and specialist cooling retailers in its home market, typically around €500.
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Page published on 3 August 2026