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Comparison
Verdict in brief
The Laars NeoTherm NTH 600 and Laars NeoTherm NTH 750 are both condensing boilers in the Laars Heating Systems NeoTherm Commercial line. Published ratings: Laars NeoTherm NTH 600 at 600,000 BTU/hr input, 572,000 BTU/hr output and 95.3% thermal efficiency; Laars NeoTherm NTH 750 at 750,000 BTU/hr input, 724,000 BTU/hr output and 96.6% thermal efficiency. Laars NeoTherm NTH 750 lists 150,000 BTU/hr more input than Laars NeoTherm NTH 600 (750,000 BTU/hr against 600,000 BTU/hr). Laars NeoTherm NTH 750 lists 1.3 percentage points more thermal efficiency than Laars NeoTherm NTH 600 (96.6% against 95.3%). Laars NeoTherm NTH 750 lists 55 lb more shipping weight than Laars NeoTherm NTH 600 (481 lb against 426 lb).
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Laars NeoTherm NTH 600 | Laars NeoTherm NTH 750 |
|---|---|---|
| Input | 600,000 BTU/hr | 750,000 BTU/hr |
| Output | 572,000 BTU/hr | 724,000 BTU/hr |
| Efficiency (thermal) | 95.3 % | 96.6 % |
| Turndown | 5:1 | 5:1 |
| Shipping weight | 426 lb | 481 lb |
| Water connection | 1-1/2" NPT | 2" NPT |
| Gas connection | 1" NPT | 1-1/2" NPT |
| Efficiency (combustion) | 96 % | 96.6 % |
Published ratings: the Laars NeoTherm NTH 600 is rated 600,000 BTU/hr input, 572,000 BTU/hr output and 95.3% thermal efficiency; the Laars NeoTherm NTH 750 is rated 750,000 BTU/hr input, 724,000 BTU/hr output and 96.6% thermal efficiency. Laars NeoTherm NTH 750 lists 150,000 BTU/hr more input than Laars NeoTherm NTH 600 (750,000 BTU/hr against 600,000 BTU/hr). Laars NeoTherm NTH 750 lists 1.3 percentage points more thermal efficiency than Laars NeoTherm NTH 600 (96.6% against 95.3%).
Laars NeoTherm NTH 750 lists 55 lb more shipping weight than Laars NeoTherm NTH 600 (481 lb against 426 lb). The water connections differs: the Laars NeoTherm NTH 600 lists 1-1/2" NPT, while the Laars NeoTherm NTH 750 lists 2" NPT. The gas connection differs: the Laars NeoTherm NTH 600 lists 1" NPT, while the Laars NeoTherm NTH 750 lists 1-1/2" NPT.
Both models are documented by the official Laars Heating Systems sources cited on their model records; the shared values above are taken from those documents.
Laars Heating Systems
The Laars NeoTherm NTH 600 is a commercial condensing boiler rated 600,000 BTU/hr input and 572,000 BTU/hr output at 95.3% thermal efficiency, with a 1" NPT gas connection, 1-1/2" NPT water connection and a 426 lb shipping weight.
Laars Heating Systems
The Laars NeoTherm NTH 750 is a commercial condensing boiler rated 750,000 BTU/hr input and 724,000 BTU/hr output at 96.6% thermal efficiency, with a 1-1/2" NPT gas connection, 2" NPT water connection and a 481 lb shipping weight.
The Laars NeoTherm NTH 750 lists 750,000 BTU/hr, against 600,000 BTU/hr on the Laars NeoTherm NTH 600, per the cited documentation.
The Laars NeoTherm NTH 750 carries the higher published thermal efficiency at 96.6%, against 95.3%.
It ships at 481 lb against 426 lb for the Laars NeoTherm NTH 600, per the cited sources.
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 9, 2026. Last updated September 9, 2026. Technical reviewer: not yet assigned.