Navien NWP500 65 Gal
#4 in 65 GallonFull review
Navien’s stainless-tank hybrid, sold through plumbers, with a 10-year warranty that includes a year of labor. Its heat pump stops below 41 °F room air, so it suits a basement more than a cold garage.
The Navien NWP500 65 Gal is the better heat pump water heater overall, rated 3.8 to 3.6. The Navien NWP500 65 Gal leads on efficiency, noise and hot water. The Ariston NUOS Side-Connect 65 Gal wins on cold rooms.
Ariston NUOS Side-Connect 65 Gal
#11 in 65 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 22, 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 Navien NWP500 65 Gal for efficiency (4.03 UEF vs 3.85 UEF), noise (45 dB(A) vs 49.1 dB(A)) and hot water (80 gallons in the first hour vs 78 gallons in the first hour).
- Choose the Ariston NUOS Side-Connect 65 Gal for cold rooms (heat pump runs down to 35 °F room air vs heat pump runs down to 41 °F room air).
Scores side by side
Each factor is scored 0-100 against the same fixed reference points for every 65 gallon heat pump water heater; a clear win is highlighted. How we rank explains each one.
| Factor weight | Navien NWP500 65 Gal | Ariston NUOS Side-Connect 65 Gal |
|---|---|---|
| Overall rating | 3.8/5 | 3.6/5 |
| Efficiency 35% | 74 4.03 UEF | 61 3.85 UEF |
| Hot water 20% | 80 80 gallons in the first hour | 72 78 gallons in the first hour |
| Warranty 20% | 75 10-year tank, 10-year parts, 1-year labor | 70 10-year tank, 10-year parts |
| Cold rooms 15% | 16 heat pump runs down to 41 °F room air | 40 heat pump runs down to 35 °F room air |
| Noise 10% | 69 45 dB(A) | 43 49.1 dB(A) |
Specifications
| Navien NWP500 65 Gal | Ariston NUOS Side-Connect 65 Gal | |
|---|---|---|
| Ratings (ENERGY STAR) | ||
| Size (nominal) | 65 gal | 65 gal |
| Tank volume (measured) | 61 gal | 62 gal |
| Uniform Energy Factor | 4.03 | 3.85 |
| First-hour rating | 80 gal | 78 gal |
| Draw pattern | High | High |
| Yearly energy use | 1,245 kWh | 1,289 kWh |
| Heat pump cut-off (low) | 41 °F | 35 °F |
| Sound level | 45 dB(A) | 49.1 dB(A) |
| ENERGY STAR ID | 4015937 | 3942614 |
| Installation | ||
| Power | 240 V | 240 V |
| Circuit | 30 A, 208/240 V | 30 A, 208/240 V |
| Backup element | 5,000 W | 4,500 W |
| Operating air range | 41 to 113 °F | 36 to 120 °F |
| Minimum room size | 640 cu ft | 700 cu ft |
| Size | 63 in tall, 25 in across | 50 in tall, 20.2 in across |
| Weight | 204 lb | - |
| Refrigerant | R-134a | R-134a |
| Features | ||
| Wi-Fi | Built in | Built in |
| App | NaviLink | Ariston NET |
| Demand response port (CTA-2045) | - | Yes |
| Leak detection | No | Yes |
| Modes | Energy Saver, Heat Pump, High Demand, Electric, Vacation | Comfort, Green, Fast, Electric, Vacation |
| Warranty and models | ||
| Warranty | 10 yr tank, 10 yr parts, 1 yr labor | 10 yr tank, 10 yr parts |
| Also sold as | - | American Standard ASHPWH-65*****, Lennox WHHP065T45MD240S**** |
| Released | 2025-06 | 2024-12 |