Ariston NUOS Side-Connect 50 Gal
#8 in 40–50 GallonFull review
A non-Midea design with a leak sensor built in and a 10-year tank and parts warranty, sold through plumbing dealers. It is louder than most here.
The Ariston NUOS Side-Connect 50 Gal is the better heat pump water heater overall, rated 3.5 to 3.3. The Ariston NUOS Side-Connect 50 Gal leads on efficiency.
Ariston NUOS Side-Connect 40 Gal
#15 in 40–50 GallonFull review
A non-Midea design with a leak sensor built in and a 10-year tank and parts warranty, sold through plumbing dealers. It is louder than most here.
Prices were last checked October 21, 2026 and are subject to change; the price and availability shown by the retailer at the time of purchase apply.
Which should you buy?
- Choose the Ariston NUOS Side-Connect 50 Gal for efficiency (3.75 UEF vs 3.58 UEF).
Scores side by side
Each factor is scored 0-100 against the same fixed reference points for every 40–50 gallon heat pump water heater; a clear win is highlighted. How we rank explains each one.
| Factor weight | Ariston NUOS Side-Connect 50 Gal | Ariston NUOS Side-Connect 40 Gal |
|---|---|---|
| Overall rating | 3.5/5 | 3.3/5 |
| Efficiency 35% | 54 3.75 UEF | 41 3.58 UEF |
| Hot water 20% | 72 68 gallons in the first hour | 64 66 gallons in the first hour |
| Warranty 20% | 70 10-year tank, 10-year parts | 70 10-year tank, 10-year parts |
| Cold rooms 15% | 40 heat pump runs down to 35 °F room air | 40 heat pump runs down to 35 °F room air |
| Noise 10% | 43 49.1 dB(A) | 43 49.1 dB(A) |
Specifications
| Ariston NUOS Side-Connect 50 Gal | Ariston NUOS Side-Connect 40 Gal | |
|---|---|---|
| Ratings (ENERGY STAR) | ||
| Size (nominal) | 50 gal | 40 gal |
| Tank volume (measured) | 45 gal | 37 gal |
| Uniform Energy Factor | 3.75 | 3.58 |
| First-hour rating | 68 gal | 66 gal |
| Draw pattern | Medium | Medium |
| Yearly energy use | 867 kWh | 907 kWh |
| Heat pump cut-off (low) | 35 °F | 35 °F |
| Sound level | 49.1 dB(A) | 49.1 dB(A) |
| ENERGY STAR ID | 3942616 | 3942613 |
| Installation | ||
| Power | 240 V | 240 V |
| Circuit | 30 A, 208/240 V | 30 A, 208/240 V |
| Backup element | 4,500 W | 4,500 W |
| Operating air range | 36 to 120 °F | 36 to 120 °F |
| Minimum room size | 700 cu ft | 700 cu ft |
| Size | 45.8 in tall, 18.2 in across | 37.6 in tall, 18.2 in across |
| Refrigerant | R-134a | R-134a |
| Features | ||
| Wi-Fi | Built in | Built in |
| App | Ariston NET | Ariston NET |
| Demand response port (CTA-2045) | Yes | Yes |
| Leak detection | Yes | Yes |
| Modes | Comfort, Green, Fast, Electric, Vacation | Comfort, Green, Fast, Electric, Vacation |
| Warranty and models | ||
| Warranty | 10 yr tank, 10 yr parts | 10 yr tank, 10 yr parts |
| Also sold as | American Standard ASHPWH-50*****, Lennox WHHP050T45MD240S**** | American Standard ASHPWH-40*****, Lennox WHHP040T45MD240S**** |
| Released | 2024-12 | 2024-12 |