Hearthstone Green Mountain 40
#18 in Wood stovesFull review
For a small to mid size home that wants long, clean catalytic burns and soapstone’s gentle heat in a compact stove.
Leisure Time $3,349 Lehman's $3,499$3,349
The Hearthstone Green Mountain 40 is the better stove overall, rated 3.3 to 2.7. The Hearthstone Green Mountain 40 leads on efficiency and emissions. The Vermont Castings Aspen C3 wins on convenience. The Vermont Castings Aspen C3 costs $1,350 less ($1,999 vs $3,349).
Vermont Castings Aspen C3
#33 in Wood stovesFull review
For a small to mid size room where the owner wants the simplest possible wood stove in classic cast iron.
Forge & Flame $1,999 Leisure Time $1,999$1,999
Prices were last checked October 31, 2026 and are subject to change; the price and availability shown by the retailer at the time of purchase apply.
Which should you buy?
- Choose the Hearthstone Green Mountain 40 for efficiency (79% EPA tested efficiency (HHV) vs 71% EPA tested efficiency (HHV)) and emissions (1.1 g/h of smoke particles (EPA) vs 1.8 g/h of smoke particles (EPA)).
- Choose the Vermont Castings Aspen C3 for convenience (takes 18 in logs, blower not stated vs takes 16 in logs, blower optional).
Scores side by side
Each factor is scored 0-100 against the same fixed reference points for every wood stoves stove; a clear win is highlighted. How we rank explains each one.
| Factor weight | Hearthstone Green Mountain 40 | Vermont Castings Aspen C3 |
|---|---|---|
| Overall rating | 3.3/5 | 2.7/5 |
| Efficiency 30% | 95 79% EPA tested efficiency (HHV) | 55 71% EPA tested efficiency (HHV) |
| Value 30% | 0 $139.54 per 1,000 BTU of EPA tested output ($3,349, 24,000 BTU) | 0 $82.26 per 1,000 BTU of EPA tested output ($1,999, 24,300 BTU) |
| Emissions 15% | 58 1.1 g/h of smoke particles (EPA) | 30 1.8 g/h of smoke particles (EPA) |
| Warranty 10% | 100 limited lifetime warranty | 50 warranty not published (neutral score used) |
| Convenience 15% | 35 takes 16 in logs, blower optional | 50 takes 18 in logs, blower not stated |
Specifications
| Hearthstone Green Mountain 40 | Vermont Castings Aspen C3 | |
|---|---|---|
| EPA certification | ||
| EPA certified | Yes (2020 standard) | Yes (2020 standard) |
| Efficiency (HHV) | 79% | 71% |
| Emissions | 1.1 g/h | 1.8 g/h |
| Tested heat output | 14,000 to 24,000 BTU | 24,300 BTU |
| Heating | ||
| Fuel | Cord wood | Cord wood |
| Type | Freestanding | Freestanding |
| Advertised output | 40,000 BTU | 39,300 BTU |
| Heats up to | 1,400 sq ft | 1,200 sq ft |
| Catalytic | Yes | No |
| Blower | Optional | - |
| Thermostat | No | No |
| App control | No | No |
| Fuel | ||
| Firebox | 1.3 cu ft | 1.2 cu ft |
| Longest log | 16 in | 18 in |
| Power needed | None | None |
| Installation | ||
| Flue size | 6 in | 6 in |
| Mobile home approved | Yes | Yes |
| Safety listing | PFS | OMNI |
| Dimensions | 23.25 x 19.375 x 30.375 in (W x D x H) | 16 x 24.25 x 25.0625 in (W x D x H) |
| Weight | 350 lb | - |
| Warranty | Limited lifetime | - |