Hearthstone Quality Home Heating Products Green Mountain 40 Series: Green Mountain 40 (8640) vs Travis Industries Liberty NexGen-Hybrid
The Travis Industries Liberty NexGen-Hybrid is the cleaner burner: 0.9 g/hr certified particulate emissions versus 1.1 g/hr. The Travis Industries Liberty NexGen-Hybrid is the more efficient unit: 80% versus 79% HHV — more heat from every cord. The Travis Industries Liberty NexGen-Hybrid produces more peak heat (47,138 vs 31,581 BTU/h), suiting roughly 1,350–1,900 sq ft. The Travis Industries Liberty NexGen-Hybrid has the larger firebox (4.14 vs 1.32 cu ft), which generally means longer burns between reloads. Combustion technology differs: the Hearthstone Quality Home Heating Products Green Mountain 40 Series: Green Mountain 40 (8640) is a hybrid and the Travis Industries Liberty NexGen-Hybrid a catalytic stove — see the catalytic vs non-catalytic guide for what that means day to day.
| Hearthstone Quality Home Heating Products Green Mountain 40 Series: Green Mountain 40 (8640) | Travis Industries Liberty NexGen-Hybrid | |
|---|---|---|
| Appliance type | wood-stove | wood-stove |
| Combustion technology | Hybrid | Catalytic Stove |
| Certified fuel | Crib Wood | Crib Wood |
| Emission rate | 1.1 g/hr | 0.9 g/hr |
| Efficiency (HHV) | 79 % | 80 % |
| Heat output (low) | 13876 BTU/h | 11598 BTU/h |
| Heat output (high) | 31581 BTU/h | 47138 BTU/h |
| Firebox volume | 1.32 cu ft | 4.14 cu ft |
| Carbon monoxide | 0.52 g/min | 0.484 g/min |
| 25C tax credit eligible (≥75% HHV) | Yes | Yes |
| 2020 NSPS compliant | Yes | Yes |
| Currently in production | Yes | Yes |
| EPA certification number | 210-19 | 381-24 |
| Covered model numbers | Green Mountain 40 Series: Green Mountain 40 (8640), Craftsbury 2 (8392), Hipster 14 (AMB8240) | Liberty NexGen-Hybrid |
Frequently asked questions
Which burns cleaner, the Hearthstone Quality Home Heating Products Green Mountain 40 Series: Green Mountain 40 (8640) or the Travis Industries Liberty NexGen-Hybrid?
The Travis Industries Liberty NexGen-Hybrid: 0.9 g/hr certified particulate emissions versus 1.1 g/hr for the Hearthstone Quality Home Heating Products Green Mountain 40 Series: Green Mountain 40 (8640).
Are the Hearthstone Quality Home Heating Products Green Mountain 40 Series: Green Mountain 40 (8640) and Travis Industries Liberty NexGen-Hybrid both EPA certified?
Yes — both appear on the U.S. EPA's current list of certified wood heaters, and every figure on this page comes from their certification records.