Bosch and Navien overlap on combi boilers and tankless. Different market positioning.
Combi boilers
| Bosch Greenstar 151 | Navien NCB-240 | |
|---|---|---|
| BTU | 151k | 240k |
| DHW GPM | 5.8 | 5.6 |
| Heat exchanger warranty | 10 years | 10 years |
| US dealer network | Moderate | Wide (combi market leader) |
| Capacity ceiling | Greenstar 151 = top | NCB-300 = top |
Navien NCB-300 (300k BTU) exceeds Bosch Greenstar 151's capacity for larger homes. For most US residential combi installs, Navien wins on dealer network and capacity options. Bosch wins on European engineering heritage and conservative design.
Tankless
| Bosch Greentherm 9999 SE | Navien NPE-240A2 | |
|---|---|---|
| BTU | 199k | 199k |
| GPM | 11.0 | 11.2 |
| Heat exchanger warranty | 15 years | 15 years |
| Buffer tank (cold-sandwich) | No | Yes (0.5 gal) |
| Built-in recirc | No | Yes |
| App | Home Comfort | NaviLink |
Navien NPE-A2 has unique buffer-tank advantage for cold-sandwich elimination. Bosch Greentherm requires external pump for recirculation. Both have 15-year warranties.
POU mini-tank
Bosch wins decisively. Navien doesn't have a POU mini-tank product. For under-sink, Bosch Tronic.
When to buy Bosch
- POU mini-tanks (only choice between these two)
- Cold-climate hydronic with European-design preference
- You have a Bosch-experienced installer
When to buy Navien
- US-volume combi boiler install (Navien is segment leader)
- Buffer-tank cold-sandwich elimination (NPE-A2)
- Built-in tankless recirculation
- Larger combi capacity (NCB-300)
Bottom line
For most US combi and tankless installs, Navien is the better-supported choice. Bosch wins on POU mini-tanks and on European combi engineering preference.