Bosch Therm 940 ES
Amazon customer rating as of
Tankless Geek editorial score: 4.3/5
The Bosch Therm 940 ES is the top of Bosch's non-condensing Therm line: 199,000 BTU/h and up to 9.4 GPM of natural-gas hot water — enough for three-plus bathrooms even in cool climates. Like its smaller sibling it uses sealed combustion and dual-fan technology for flexible 3- or 4-inch stainless venting (side-wall or roof), with electronic ignition, built-in freeze protection, and an externally accessible water filter. It measures 30½ × 17¾ × 11¼ inches and weighs about 67 pounds.
At roughly 83% thermal efficiency it's non-condensing — so no condensate drain, but more gas per gallon than a condensing unit and stainless (not PVC) venting. What you get for that is one of the highest flow rates here without the price and plumbing of a condensing heater, backed by a long heat-exchanger warranty. As with the 830 ES, note the Therm ES generation is legacy and being phased out; check availability and parts before buying.
Key Features
Best Use Cases
Our Verdict
The high-capacity pick in Bosch's non-condensing line — 9.4 GPM for a large home without a condensate drain. A strong value where flow matters more than squeezing out maximum efficiency. Plan for stainless venting, and confirm parts/availability since it's an older model line.
Technical Specifications
| Input | 199,000 BTU/h (natural gas) |
|---|---|
| Max flow | Up to 9.4 GPM (at 35 °F rise) |
| Efficiency | ≈83% thermal, non-condensing · ENERGY STAR |
| Venting | 3–4 in stainless; side-wall or roof |
| Dimensions | 30.5 × 17.75 × 11.25 in, ≈67 lb |
| Extras | Sealed combustion, freeze protection, external filter |
Specifications verified against the linked source documents. See Sources below.
How much hot water you'll actually get
Usable flow drops as incoming water gets colder. Figures are calculated from rated output (199,000 BTU × 0.82 UEF) and labeled as such — not bench-tested by us.
| Temperature rise | Typical scenario | Usable flow |
|---|---|---|
| 35 °F | Warm climate (75 °F in → 110 °F) — capped at max | 9.4 GPM |
| 45 °F | Mild climate (65 °F in → 110 °F) | 7.3 GPM |
| 60 °F | Cool climate (50 °F in → 110 °F) | 5.4 GPM |
| 70 °F | Cold climate (40 °F in → 110 °F) | 4.7 GPM |
Usable flow at a 110 °F target: BTU × thermal-eff ÷ (ΔF × 500), capped at the 9.4 GPM maximum. Non-condensing efficiency (~82–83%) is applied.
Pros
Cons
Buy it if…
- Large homes running 3+ bathrooms in warm to cool climates
- Buyers wanting maximum flow without condensing plumbing
- Installs favoring flexible side-wall or roof stainless venting
- Households that value freeze protection and an external filter
Skip it if…
- Efficiency-focused buyers (a condensing unit will cost less to run)
- Very cold climates needing full 9.4 GPM at a deep temperature rise
- Anyone needing guaranteed long-term parts from a current line
Installation Requirements
Professional vs DIY
Full-size gas input and stainless venting mean a licensed installer — DIY gas/vent work risks safety and the warranty.
Gas and electrical work should be done by a licensed professional, and most installs require a permit and must meet local building codes — DIY work can void the manufacturer warranty. Always confirm the unit's own manual for exact clearances, venting, and sizing.
What owners report
Themes summarized from retailer customer feedback (4/5 Amazon customer rating, 67 ratings, as of 2026-08-23). These are owner opinions, not our own bench testing.
Owners praise the 199,000 BTU burner for running several fixtures at once without temperature drop in warm and mild climates.
Sealed combustion and dual-fan design allow side-wall or roof venting and installation in tighter spaces.
At ~83% thermal efficiency it uses more gas per gallon than a condensing unit and requires stainless venting — the cost of the higher flow at a lower price.
The Therm ES line is being phased out; owners and installers should confirm parts and service availability.
Bosch Therm 940 ES FAQ
How many bathrooms can the 940 ES run?+
Up to about 9.4 GPM in warm/mild climates — comfortably three or more bathrooms at once. In cold weather deliverable flow drops toward 4.7–5.4 GPM.
Is it condensing?+
No. It's non-condensing at roughly 83% thermal efficiency — no condensate drain, but it needs 3–4 inch stainless venting and uses more gas per gallon than a condensing model.
How big is it and where can it go?+
About 30.5 × 17.75 × 11.25 inches and 67 pounds, with sealed combustion allowing flexible side-wall or roof venting for varied install locations.
Is it still available?+
It's a legacy Therm ES model still sold through supply channels but being phased out — verify stock and parts support before purchasing.
Product sources
Specifications verified 2026-08-23. Manufacturer documents are treated as the primary source for model specifications. Retailer pages are used only for customer ratings and owner-feedback themes.
- Bosch 940 ES installation & operating manual (dimensions) (accessed 2026-08-23)
- Bosch Therm 940 ES NG 199,000 BTU — SupplyHouse (accessed 2026-08-23)
- Bosch Therm 940 ES — HVACDirect listing (accessed 2026-08-23)
Price range from leading retailers
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