Boilers
Bosch Greenstar ZWB-28-3 Condensing Combi Boiler
8 of 10 catalog products carry at least one real, seller-observed equipment-only price (SupplyHouse, Active Plumbing, Home Depot, AF Supply), gathered 2026-08-24 -- 80% against the >=70% gate. Two products (weil-mclain-evergreen, htp-elite-premier-ep110) were researched but no real seller price could be reached (login-gated distributor pages) and were left unpriced rather than estimated, per this platform's own rule against silent substitution. A genuine, disclosed limitation found this run: platform/core/pricing.py's PER_TON_BANDS dictionary defines $/ton plausibility floors and ceilings for heat-pump, mini-split, central-ac and furnace only -- boiler (and solar-panel) have no band defined at all. Confirmed by reading validate_observation() directly: when bands.get(scope) returns None for an unbanded category, the function returns (True, None) unconditionally, so every boiler price observation currently passes validation regardless of its $/ton figure. This means the exact failure mode PROCEDURE.md documents for heat-pump (a $1,707-for-a-3-ton listing that was actually a financing figure) could not be caught here even if it existed, because no floor exists to catch it. Not silently patched -- platform/core/ pricing.py was read but not edited as part of this pass, per instructions. For reference, this run's own 8 real observations imply a $/ton range of roughly $124-$684 (Rheem Prestige RCBH199DVLN's $2,048 list at 199,000 BTU/h is the low outlier worth a second look before trusting it as-is; IBC SL 260's $6,163.53 at 260,000 BTU/h is the high end). A future pass should propose a real boiler band -- something in the neighborhood of $150-$900/ton would bracket what this run actually observed with margin -- rather than leave the category permanently unchecked.
Compact wall-hung condensing combi boiler, Bosch's current US residential line replacing the discontinued Buderus GB142.
Our take
Buderus's GB142 (the model most comparison articles still cite) has been discontinued since 2018; Greenstar is the line Bosch actually sells today, at a smaller nominal capacity than the old GB142 range. A straightforward, well-supported German-engineered wall-hung unit for a smaller home or a zoned system that doesn't need a large single boiler.
Best for
Smaller homes or a single heating zone where a compact wall-hung combi covers the whole load.
Watch out for
At 79,000-100,000 BTU/h output this is on the small side for this catalog — confirm it covers your actual heat loss before buying on brand reputation alone.
What sellers are actually charging
Real listings, read on the date shown. Prices change — click through to check before you act on any of them.
| Seller | What you get | Price | Seen |
|---|---|---|---|
| SupplyHouse.com
online retailer |
Bosch Greenstar 100 ZWB-28-3 combi boiler
ZWB-28-3 |
$5,531 | 2026-08-16 |
Equipment price is not installed price. The listings above are what the hardware costs. Installation — labour, electrical, refrigerant lines, permits, removing the old system — is typically a similar amount again, and varies more between contractors than between brands. Where we have an installed figure it is labelled as such and comes from someone who actually installs.
Compare against
Lochinvar Knight Fire Tube Condensing Boiler
Fire-tube condensing boiler with 10:1 turndown, built for the residential and light-commercial hydronic market.
Navien NFC-175 Condensing Combi Boiler
High-turndown condensing combi boiler providing both hydronic heat and domestic hot water from one wall-hung unit.
Viessmann Vitodens 100-W Condensing Boiler
German-engineered condensing boiler with a stainless Inox-Radial heat exchanger and a 10:1 turndown ratio in line with the rest of this catalog's condensing boilers.
Weil-McLain Evergreen Condensing Boiler
Stainless condensing boiler from the most established US residential boiler brand.
Before you buy this
Ask about turndown ratio, not just efficiency — a boiler that can't modulate down to your house's actual heat loss on a mild day short-cycles, and short-cycling is what wears a boiler out early. Confirm whether your radiators or baseboard were sized for the supply temperature this boiler will actually deliver. And ask for a heat-loss calculation instead of matching the old unit's output.