ComfortBilt HP21 Pellet Stove

The ComfortBilt HP21 pellet stove is a compact, pedestal-style stove from ComfortBilt's HP line, with a wide bay-view window. It heats up to 2,400 sq ft and delivered 12,349 to 31,753 BTU/h in EPA testing. Its 40 lb hopper runs up to 16 hours on the lowest of five heat levels. It is EPA 2020 certified at 1.47 g/h with a tested efficiency of 76.3% (HHV). Automatic ignition, a room blower, a programmable control panel and an infrared remote are standard. It vents through 3" pellet pipe and is approved for mobile homes with an outside air connection. Choose the all-black Standard finish or the Stainless Trim around the window; the stove behind it is the same.

Who the HP21 is for

• Smaller homes, cabins and additions where the main living space is open to the stove.
• Zone heating a living area, finished basement or workshop to cut furnace or propane run time.
• Buyers who want thermostat-controlled pellet heat without paying for a bigger stove than they need.

ComfortBilt's 2,400 sq ft rating assumes mild weather. Climate, insulation and layout all move the real number. In a cold climate, size the HP21 for the open area around it rather than the whole house. It needs electricity, so ComfortBilt advises keeping another heat source for power outages.

Hopper, burn time and heat output

The 40 lb hopper holds about one standard bag of pellets. ComfortBilt rates it at up to 16 hours on heat level 1; on the higher levels expect to refill once or twice a day in cold weather.

The output range matters as much as the peak. The HP21 idles at about 12,300 BTU/h, which keeps a smaller space comfortable in fall and spring without overheating it, and climbs past 31,000 BTU/h when it is cold. If even level 1 is too much, turn on ECO in Temp mode and the stove will shut off at your set temperature and re-light when the room cools (more restarts mean more igniter wear).

Controls, remote and thermostat

The control panel runs four modes: Manual (heat levels 1 to 5), Temp (set 61°F to 82°F and the stove adjusts itself from its room sensor), Weekly (a 7-day schedule with up to four periods a day) and Thermostat (a wired wall thermostat lights and stops the stove).

The included infrared remote handles on/off, Manual or Temp mode and the heat level or set temperature. For a thermostat that reads the temperature where you sit, add the ComfortBilt CB3002 wireless remote thermostat. For phone control, the BC Innovate WiFi module fits stoves with the newer 4-pin control panel; check the back of your panel before ordering.

HP21 vs. HP50S vs. HP22

The two ComfortBilt models closest to the HP21, with figures from each owner's manual:

↔ Swipe the table to see more →

The HP50S has the same 2,400 sq ft rating, higher efficiency and a slightly bigger hopper, but its lowest output is about 5,000 BTU/h higher than the HP21's, so the HP21 is the gentler choice for a small space. The HP22 turns down further still, to 9,696 BTU/h, while reaching 40,689 BTU/h at the top, and adds 15 lb of hopper; it is the better buy if you are heating closer to 2,800 sq ft or want fewer refills. For an 80 lb hopper, see the ComfortBilt HP22N.

Venting and installation

The HP21 has a 3" exhaust and a 2" air intake. Connect a 3" appliance adapter to the exhaust, then run listed Type L or PL pellet vent; our ComfortBilt / DuraVent 3" pellet vent kit covers a standard through-wall install. ComfortBilt's main rules:

• Switch to 4" vent if the vertical run is over 12 ft, the home is above 5,000 ft elevation, or the run has more than one tee or more than 180° of elbows.
• Keep the run short: the maximum equivalent vent length is 17 for 3" pipe and 27 for 4" (a 90° elbow counts as 5 ft of horizontal pipe).
• No more than 4 ft of horizontal run. At least 3 ft of vertical rise is recommended so the stove drafts naturally in a power outage.
• Clearances to combustibles: 2" from the back wall to the stove back, 5" to the rear corners and 7" to side walls (see the clearance table below).
• Mobile homes need an outside air connection, and the stove bolted down and grounded to the chassis. Never install in a bedroom.

Our pellet stove venting guide walks through through-wall and vertical layouts.

Floor protection

Unless the stove sits on a non-combustible floor, it needs a non-combustible floor protector under the stove that extends at least 6" in front of the glass and 6" past each side. With an inside clean-out tee, the pad must also reach 2" beyond the tee. With the HP21's 23 1/2" width, that means a pad at least 35 1/2" wide: the ComfortBilt 36" hearth pad fits flat-wall installs and the ComfortBilt 40" corner hearth pad fits corner placements. The HP21 + hearth pad combo bundles either one and saves $99. See all hearth pads or our hearth pad guide.

Why buy the ComfortBilt HP21 from StoveSource

• No Sales Tax in any state.
• Free shipping to the lower 48. ComfortBilt stoves ship fast: Ships in 1–3 days.
• Free ComfortBilt B67C vent cleaning kit with your stove.
• Authorized ComfortBilt dealer, with ComfortBilt's warranty: 1 year on electrical parts, the burn pot and labor, and 5 years on steel parts.
• Price match guarantee.
• Help with sizing, venting and clearances: email info@stovesource.com or text 1-888-866-8206.