AC Infinity CLOUDLINE S4
#2 in 4 inFull review
A quiet, efficient 4 in fan for small grow tents, closets and AV cabinets. The S line adds a longer cord and more airflow than the cheaper A4.
Amazon $89.99$89.99
The AC Infinity CLOUDLINE S4 is the better inline duct fan overall, rated 3.6 to 2.8. The AC Infinity CLOUDLINE S4 leads on efficiency, airflow and value. The AC Infinity CLOUDLINE A4 costs $10 less ($79.99 vs $89.99).
Prices were last checked November 9, 2026. Product prices and availability are accurate as of that date and are subject to change; the price and availability shown on Amazon or the retailer's site at the time of purchase apply. As an Amazon Associate we earn from qualifying purchases.
AC Infinity CLOUDLINE A4
#6 in 4 inFull review
The budget member of the CLOUDLINE 4 in range, with the same controller and build but less airflow than the S4. Worth it for its higher static pressure behind a small carbon filter.
Amazon $79.99$79.99
Which should you buy?
- Choose the AC Infinity CLOUDLINE S4 for efficiency (8.1 CFM per watt (226 CFM, 28 W) vs 4.7 CFM per watt (165 CFM, 35 W)), airflow (226 CFM through 4 in duct vs 165 CFM through 4 in duct) and value ($39.82 per 100 CFM ($89.99, 226 CFM) vs $48.48 per 100 CFM ($79.99, 165 CFM)).
Scores side by side
Each factor is scored 0-100 against the same fixed reference points for every 4 in inline duct fan; a clear win is highlighted. How we rank explains each one.
| Factor weight | AC Infinity CLOUDLINE S4 | AC Infinity CLOUDLINE A4 |
|---|---|---|
| Overall rating | 3.6/5 | 2.8/5 |
| Value 25% | 47 $39.82 per 100 CFM ($89.99, 226 CFM) | 24 $48.48 per 100 CFM ($79.99, 165 CFM) |
| Efficiency 25% | 56 8.1 CFM per watt (226 CFM, 28 W) | 19 4.7 CFM per watt (165 CFM, 35 W) |
| Airflow 15% | 88 226 CFM through 4 in duct | 38 165 CFM through 4 in duct |
| Noise 15% | 97 26 dBA at full speed | 89 29 dBA at full speed |
| Controls 10% | 40 speed controller included | 40 speed controller included |
| Warranty 10% | 25 2-year warranty | 25 2-year warranty |
Specifications
| AC Infinity CLOUDLINE S4 | AC Infinity CLOUDLINE A4 | |
|---|---|---|
| Performance | ||
| Duct size | 4 in | 4 in |
| Rated airflow | 226 CFM | 165 CFM |
| Static pressure (not scored) | 223 Pa | 324 Pa |
| Power at full speed | 28 W | 35 W |
| Power figure | Max power draw | Max power draw |
| Average power (not scored) | 21 W | 18 W |
| Airflow per watt | 8.1 CFM/W | 4.7 CFM/W |
| Price per 100 CFM | $39.82 | $48.48 |
| Noise at full speed | 26 dBA | 29 dBA |
| Top speed | 2,800 RPM | 2,800 RPM |
| Controls | ||
| Motor | EC | EC |
| Controller | 10-speed controller | 10-speed controller |
| Speeds | 10 | 10 |
| Temperature and humidity control | No | No |
| Phone app | No | No |
| Timer or cycle modes | No | No |
| Build | ||
| Housing | Plastic | Plastic |
| Ingress rating | IP44 | IP44 |
| Voltage | 100-240 V | 100-240 V |
| Warranty | 2 years | 2 years |