Both are heat pump water heaters. The NWP500S065AUMB is more efficient (UEF 4.03 vs 3.90). The REHP65BM saves $1/year to operate. All figures from published specs and EIA energy prices. UEF measures lab efficiency under DOE test conditions. Annual cost uses that rating plus national average energy prices. Different draw patterns, local rates, and standby losses can cause the rankings to diverge.
Performance
| Spec | NWP500S065AUMB Navien · Heat Pump | REHP65BM Rinnai · Heat Pump |
|---|---|---|
| UEF | 4.03Difference: 0.13 | 3.90 |
| Capacity | 61 galDifference: 1 gal | 60 gal |
| First Hour Rating | 80 galidentical | |
| kW Input | 5 kWDifference: 0.50 kW | 5.50 kW |
The NWP500S065AUMB leads on efficiency. But does it fit? Sizing guide
Physical dimensions
| Dimension | NWP500S065AUMB | REHP65BM |
|---|---|---|
| Height | 63"Difference: 2.50" | 65.50" |
| Width | 25"Difference: 0.60" | 25.60" |
| Depth | 25"Difference: 0.69" | 25.69" |
| Weight | 204 lbsDifference: 46 lbs | 250 lbs |
The REHP65BM is taller. Fit checked. Now the operating cost.
Operating cost
| Cost | NWP500S065AUMB | REHP65BM |
|---|---|---|
| Annual Operating Cost | $215/yr | $214/yrDifference: $1/yr |
| 10-Year Operating Cost | $2,150 | $2,140Difference: $10 |
| Annual Energy | 1,245 kWh | 1,240 kWhDifference: 5 kWh |
10-year modeled difference is $10. At this scale, local energy rates, usage patterns, and install costs matter more than the efficiency delta.
Costs vary by state. The NWP500S065AUMB ranges from $137/yr (ND) to $518/yr (HI). The REHP65BM ranges from $137/yr (ND) to $516/yr (HI).
$1/yr separates them. Install requirements determine the upfront gap. Installation accessories
Installation requirements
| Requirement | NWP500S065AUMB | REHP65BM |
|---|---|---|
| Voltage | 240Videntical | |
| Amperage | 23ADifference: 1A | 24A |
| Breaker | 30Aidentical | |
| Condensate Drain | Yes | — |
Same electrical requirements. Swapping between these units should not require electrical changes.
Warranty
| Coverage | NWP500S065AUMB | REHP65BM |
|---|---|---|
| Tank | 10 yridentical | |
| Parts | 10 yridentical | |
| Labor | 1 yridentical | |
Features
| Feature | NWP500S065AUMB | REHP65BM |
|---|---|---|
| Wi-Fi / Smart | Yesidentical | |
| Noise Level | 45 dB | — |
| Refrigerant | R-134aidentical | |
Decision split
Pick this one if...
Navien NWP500S065AUMB
- Your ceiling or space is under 65.50"
- Peak efficiency is the priority (UEF 4.03)
Neither if...
- Your home only has 120V service and you cannot upgrade the panel
- Your install space is under 700 sq ft of open air
Common accessories for this type of installation.
Common install considerations for heat pump units
What is required depends on your existing installation, local code, and installer preference.
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Related
Sources. ENERGY STAR, manufacturer spec sheets, EIA average energy prices.Methodology