Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
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Comparison
Verdict in brief
The step from the B1HE-120 to the B1HE-150 buys 30 MBH of input ceiling (150 vs 120 MBH maximum) but costs you the compact cabinet: the 150 weighs 179 lb against 108 lb and stands 39 inches tall instead of 33.75, with its minimum fire rising from 12 to 15.5 MBH. Both are 95% AFUE heating-only models, so the heat-loss calculation must justify the bigger unit.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Viessmann Vitodens 100-W B1HE-120 | Viessmann Vitodens 100-W B1HE-150 |
|---|---|---|
| Input, minimum (natural gas) | 12 MBH | 15.5 MBH |
| Input, maximum (natural gas) | 120 MBH | 150 MBH |
| Efficiency (AFUE) | 95 % | 95 % |
| Weight | 108 lb | 179 lb |
| Domestic hot water | Not a combi; pair with an indirect tank | Not a combi; pair with an indirect tank |
Both boilers sit on the same Vitodens 100-W platform with the same 95% AFUE rating, burner and heat exchanger, and both are heating-only. The 120 fires 12 to 120 MBH (3.5 to 35.2 kW); the 150 fires 15.5 to 150 MBH (4.5 to 44.0 kW), so the comparison is capacity and the installation cost of getting it.
The 150 moves to the larger chassis: 179 lb (81 kg) against 108 lb (49 kg), 39 inches tall and 21.75 inches deep versus 33.75 and 19.75 inches. The wall mounting, handling and the doorways into the mechanical room all change, and the minimum fire rises from 12 to 15.5 MBH.
Because Viessmann Canada quotes vent runs up to about 180 ft across the series, venting rarely separates the two models. What separates them is the calculated load: a home that needs more than 120 MBH on a design day, or a large indirect tank to recover, justifies the 150; otherwise the 120's lower minimum fire condenses more often in mild BC weather.
Viessmann
The Vitodens 100-W B1HE-120 is the mid-range heating-only model of Viessmann Canada's 100-W series: 12 to 120 MBH input, 95% AFUE, 108 lb, in the same compact cabinet as the B1HE-85.
Viessmann
The Vitodens 100-W B1HE-150 is the 150 MBH heating-only model of Viessmann Canada's 100-W series: 15.5 to 150 MBH input at 95% AFUE, stepping up to a 179 lb, 39-inch-tall cabinet for larger detached homes.
179 lb (81 kg) versus 108 lb (49 kg), per Viessmann Canada. The 150 is also 5.25 inches taller and 2 inches deeper, so the mounting and access plan differs.
Yes. The 120 fires down to 12 MBH and the 150 only to 15.5 MBH, so in a low-load home the 120 tracks mild weather more closely even though both are rated 95% AFUE.
When the room-by-room heat-loss calculation plus hot-water recovery demand exceeds the 120's ceiling. Sizing beyond the calculated load just reduces condensing time.
A consultation includes a heat-loss review so the size is right the first time.
On-site service in Greater Vancouver, BC. ROMA lists “Open 7 days” on its site; call to confirm same-day availability.
Sources and verification
Facts checked September 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.