Almost every ethanol project that comes through our Maspeth showroom gets stuck on the same question: which EcoSmart burner goes in this opening? The EcoSmart Fire lineup looks simple until you put the spec sheets side by side. Seven bare burners, three shapes, heat outputs from 5,800 to over 20,000 BTU, and tank sizes from under a gallon to more than two and a half.
This guide is the selector we use with customers. It covers every ethanol burner EcoSmart currently makes (AB3, AB8, BK5, XL500, XL700, XL900, XL1200), the grates and Heritage inserts built around them, the Flex fireboxes, the fuel math on e-NRG, and the clearance and box rules from EcoSmart's installation guidance. If you are still deciding whether ethanol is right for you at all, start with our ethanol fireplace buying guide and come back here when you are ready to pick a model.
The short answer
Pick the EcoSmart burner by the interior width of the box it goes in, then confirm the room is big enough. Linear XL burners (XL500, XL700, XL900, XL1200) suit wide modern openings and feature walls; the square BK5 and AB8 suit traditional fireboxes and fire tables; the small AB3 suits compact niches and small rooms. A full tank lasts 7 to 14 hours depending on the model, and the burners use 0.08 to 0.29 gallons of e-NRG an hour at full flame. For a typical 42 inch opening, the XL700 is the right fit.
Key takeaways
- Measure the inside of the box, not the opening face. EcoSmart's firebox offsets add about 12 inches to the length of any XL burner.
- Minimum room volume runs from 1,413 cubic feet (AB3) to 4,097 cubic feet (AB8). The room decides the burner as often as the opening does.
- Every burner needs EcoSmart's top tray indoors, a non-combustible box, and at least 59 inches between the flame and curtains or anything that moves.
- Fuel use at full flame ranges from about a third of a quart an hour (AB3) to just over a quart an hour (AB8). Turning the flame down, or adding the included baffles or efficiency ring, stretches every fill.
- Never refill a lit or warm burner. EcoSmart says shut it off and let it cool 60 minutes first.
- All seven burners are manual. If you want a fireplace that arrives finished, a Heritage insert or a grate saves you from building a box at all.
In this guide
- Quick pick: which burner for which job?
- What is the difference between the XL, AB and BK burners?
- What size burner fits my opening or custom box?
- Burner, grate, Heritage insert or Flex firebox?
- How much e-NRG does a burner use, and how long does a fill last?
- What clearances and ventilation does a burner need?
- How do you refuel safely?
- Will my NYC co-op or condo allow it?
- Our recommended models
- Which should you choose?
- Frequently asked questions
Quick pick: which burner for which job?
Start here. Find the line that sounds like your project, then read the sections below to confirm the box size and room volume.
| Your project | Start with | Why |
|---|---|---|
| Small niche, bookshelf bay or a bedroom | AB3 | Lowest heat (5,800 BTU) and the smallest room minimum in the range |
| Existing prewar fireplace, traditional look | Heritage insert or Heritage Grate 25 (BK5 inside) | Square flame on logs, no box to build |
| Custom box about 32 to 39 inches wide inside | XL500 | Longest burn per fill of the XL family at 10 to 13 hours |
| Standard 42 inch opening | XL700 or Grate 36 | The 27.6 inch burner clears EcoSmart's offsets in a 42 inch box |
| Linear feature wall, 48 to 58 inch box | XL900 | 35.7 inch flame, 15,000 BTU, 8 to 13 hours |
| Long media wall or large open plan | XL1200 | 47.2 inch flame, biggest tank, up to 14 hours |
| Most heat in a large room, or a fire table | AB8 | 20,433 BTU, the hottest burner EcoSmart makes |
What is the difference between the XL, AB and BK burners?
Shape and size. All seven are manual stainless steel reservoirs (Grade 304, with an optional black ceramic finish) that you fill from a jerry can and light with a rod. All are listed to UL 1370, the U.S. standard for unvented alcohol fuel decorative appliances, and certified to EN 16647 in Europe. What changes is the flame footprint, the tank and the heat.
- XL series is linear. Four lengths share a 7.7 inch width and 4.4 inch depth, so they drop into the same style of slot. This is the family for modern openings, plaster niches and long wall fires.
- AB series is square and comes in two very different sizes: the compact AB3 and the high output AB8. The AB8 ships with an efficiency ring that lowers the flame and heat and stretches burn time.
- BK5 is square too, sized between the two AB burners. It is the burner inside the Heritage inserts and the Heritage Grate 25, which is why it reads as a "traditional" fire.
Here are EcoSmart's published numbers for each. EcoSmart notes these figures are indicative and vary with installation and flame setting.
| Burner | Burner size (in) | Heat | Tank | Burn per fill | Min. room |
|---|---|---|---|---|---|
| AB3 | 10.2 x 10.2 | 5,800 BTU/h | 0.7 gal | 8 to 11 h | 1,413 cu ft |
| BK5 | 11.4 x 11.4 | 13,000 BTU/h | 1.3 gal | 7 to 11 h | 2,472 cu ft |
| AB8 | 14.2 x 14.2 | 20,433 BTU/h | 2.1 gal | 7 to 9 h | 4,097 cu ft |
| XL500 | 19.7 x 7.7 | 11,430 BTU/h | 1.3 gal | 10 to 13 h | 2,825 cu ft |
| XL700 | 27.6 x 7.7 | 13,650 BTU/h | 1.8 gal | 9 to 12 h | 3,178 cu ft |
| XL900 | 35.7 x 7.7 | 15,000 BTU/h | 2.4 gal | 8 to 13 h | 3,885 cu ft |
| XL1200 | 47.2 x 7.7 | 15,290 BTU/h | 2.6 gal | 9 to 14 h | 4,061 cu ft |
Two things jump out. First, the XL burners do not scale heat with length. Going from the XL900 to the XL1200 adds almost a foot of flame but under 300 BTU, so the bigger burner buys you a longer fire, not a hotter room. Second, the AB8 is in a class of its own for heat. At 20,433 BTU it outputs more than three times what the AB3 does, and it needs nearly three times the room volume.
Room volume is length times width times ceiling height in feet. A 14 by 18 foot living room with 9 foot ceilings is 2,268 cubic feet, which clears only the AB3 on its own. Open it to a dining area and it climbs fast. If your room comes in under the burner's minimum, step down a model. That is EcoSmart's published floor, not a suggestion.
Shop ethanol burnersAll EcoSmart Fire
What size burner fits my opening or custom box?
This is where most online advice goes wrong. People match the burner length to the opening and forget that EcoSmart requires space around the burner inside a firebox. Their offset table, measured from the outer edge of the burner flange, calls for these minimums:
- XL series: 5.9 inches each side, 2.0 inches front, 1.6 inches rear.
- BK5: 4.9 inches each side, 1.8 inches front, 1.2 inches rear.
- AB8: 5.7 inches each side, 1.8 inches front, 1.2 inches rear.
- AB3: 2.8 inches each side, 1.8 inches front, 1.2 inches rear.
Add those to the burner dimensions and you get the smallest interior box each burner can live in. EcoSmart recommends centering the burner, so treat these as floors and give yourself a little extra.
| Burner | Min. interior width | Min. interior depth | Fits a box roughly |
|---|---|---|---|
| AB3 | 15.8 in | 13.2 in | 16 to 21 in wide |
| BK5 | 21.2 in | 14.4 in | 21 to 26 in wide |
| AB8 | 25.6 in | 17.2 in | 26 in and up, deep boxes |
| XL500 | 31.5 in | 11.3 in | 32 to 39 in wide |
| XL700 | 39.4 in | 11.3 in | 40 to 47 in wide |
| XL900 | 47.5 in | 11.3 in | 48 to 58 in wide |
| XL1200 | 59.0 in | 11.3 in | 59 in and up |
So, the question we get most: what burner for a 42 inch opening? If the interior is truly 42 inches wide, the XL700 fits with a little room to spare and the XL900 does not. If 42 inches is the outside of the trim and the inside is closer to 38, you are in XL500 territory. Measure the inside, at the back wall as well as the front, because prewar fireboxes often taper.
A custom box has its own rules too. EcoSmart wants it built from non-combustible material such as steel, sized to take the top tray, with 20 mm (about 0.8 inch) spacers on all sides and an air gap that is never packed with insulation. The cut-out for the top tray should be within 5 mm (about 0.2 inch) of the tray. If you add glass, EcoSmart calls for a static windscreen 7 to 9 inches high across the full width and a 1.6 inch gap between the burner platform and the underside of the glass.
From our install team
When a millworker or GC builds the box, we send the burner's top tray dimensions and the offset table before anyone cuts steel. The most common fix we make in the field is a box that matches the burner length exactly, with no side clearance. It looks great on the drawing and fails the offsets on day one.
Burner, grate, Heritage insert or Flex firebox?
A bare burner is only one way to buy EcoSmart. If you do not want to design a box, one of these may already be built around the right burner.
Grates, for an existing masonry fireplace
EcoSmart's fireplace grates put a burner inside a steel log grate that sits on your hearth. Each one is tied to a specific burner:
- Grate 18: holds the AB8, 18 by 16 inches, the hottest grate.
- Grate 30: holds the XL500, 30 by 13 inches.
- Grate 36: holds the XL700, 36 by 13 inches.
- Heritage Grate 25: holds the BK5 with a log set, 24.8 by 18.4 inches.
- Heritage Grate 50: pairs with the XL900 for wide openings.
The heat, burn time and room minimum are the same as the burner inside, so use the burner table above. Measure your hearth at the back and front and make sure the grate footprint fits with space around it.
Heritage inserts, a finished firebox
The Heritage series is a black steel firebox with a grate, logs, glass screen and burner configuration already designed, for a mantel or a new chase. The Heritage 26SS (33.9 inches wide) and Heritage 42SS (49.9 inches wide, about 127 pounds) are built for the BK5. The Heritage 56SS (63.9 inches wide) is built for the XL900. All three are 21.2 inches deep. Browse the full set under ethanol fireplace inserts.
Flex fireboxes, zero clearance with the burner included
Flex is EcoSmart's architectural firebox: a powder coated steel box that EcoSmart describes as true zero clearance, in single sided, double sided, corner, peninsula, bay, island and bench formats. You do not buy a burner separately; it comes configured. The Flex 50SS, for example, is offered as "all flame" with an XL900 or as box left or box right with an XL500, and ships with baffles, a jerry can and a lighting rod. Flex models are special order and not listed in our online store right now, so call us with your wall dimensions and we will spec one.
Shop ethanol gratesShop ethanol insertsShop ethanol fire tables
Fire tables use the same burners. The Manhattan 50, for example, runs an AB8, so expect the same 7 to 9 hour burn. Indoors, EcoSmart calls for its indoor safety tray and the AB8 efficiency ring on that table, and EcoSmart fire pits and fire bowls are outdoor only.
How much e-NRG does a burner use, and how long does a fill last?
The spec sheets give maximum consumption in gallons per hour. Since e-NRG bioethanol is sold by the quart, here is the same data in quarts, plus how long a 16 quart case lasts if you run wide open the whole time.
| Burner | Full fill | Max use per hour | Hours per 16 qt case at full flame |
|---|---|---|---|
| AB3 | 2.8 qt | 0.32 qt | About 50 |
| XL500 | 5.2 qt | 0.52 qt | About 31 |
| BK5 | 5.2 qt | 0.68 qt | About 23 |
| XL700 | 7.2 qt | 0.72 qt | About 22 |
| XL900 | 9.6 qt | 0.84 qt | About 19 |
| XL1200 | 10.4 qt | 0.92 qt | About 17 |
| AB8 | 8.4 qt | 1.16 qt | About 14 |
To get your cost per hour, multiply the "max use per hour" figure by what you pay per quart. That is a worst case. Most people run the flame below maximum after the first half hour, and the XL baffles and AB8 efficiency ring that come in the box lower the flame and heat on purpose. EcoSmart says the ring increases burn time; the baffles do the same job on the XL.
A realistic season for a household that lights an XL900 three hours a night, four nights a week, at full flame, is about 10 quarts a week. Turn it down and that drops noticeably. Plan storage around that number, because you do not want a closet full of flammable liquid in an apartment (more on that below).
Can you use another bioethanol? EcoSmart's safety instructions say its appliances use only e-NRG and nothing else, and its support team notes that other fuels vary in purity and additives and can give a lower, dimmer flame. Gel fuel and denatured hardware store alcohol do not belong in these burners. Stick to e-NRG and you keep the flame EcoSmart tested.
Not sure what fits your space? Send us the inside width and depth of your opening and the room dimensions, and we will tell you which burner clears the offsets and the room minimum. Book a free design consultation and we will help you narrow it down.
What clearances and ventilation does a burner need?
No chimney, no flue, no gas line and no electrical connection. That is the appeal. But EcoSmart's installation guidance still sets firm rules:
- Top tray indoors. Every burner needs its own top tray before it is lit indoors. The tray cannot exceed 200 percent of the burner's size.
- Curtains and anything that moves: at least 1,500 mm (59.1 inches) from the flame indoors, overhead and around. Outdoors, overhead clearance goes to 2,000 mm (78.7 inches) to allow for branches and umbrellas.
- Fixed furniture and combustible materials: at least 600 mm (23.6 inches) to the side for the BK5, XL and AB series.
- Surrounding materials: non-combustible only, such as steel, concrete, brick or natural stone. No unrated wallpaper, laminate or veneer, and any glass or mirror nearby must be toughened.
- Air: EcoSmart says to use the burner only in well ventilated areas protected from cross drafts, and to meet the minimum room volume for the model. Drafts from an open window or an HVAC supply make the flame lean and flicker.
Combustion of ethanol gives off heat, water vapor and carbon dioxide, with no smoke or soot. That is why there is no vent, and also why the room volume minimums exist. If your apartment is a tight new build with sealed windows, give the burner more room than the minimum, not less.
From our install team
The clearance that catches people is the TV. A burner in a niche under a television puts heat straight up into the screen. EcoSmart publishes a separate TV installation flyer for this; we follow it and usually recommend a mantel or a recess shelf to break the heat plume.
How do you refuel safely?
Almost every ethanol accident you read about is someone pouring fuel into a burner that is still lit or still hot. Ethanol flame can be nearly invisible in a bright room. EcoSmart's rules are short and non-negotiable:
- Close the lid with the lighting rod hook to put the fire out. Do not assume it is out because you cannot see it.
- Let the burner cool 60 minutes before refueling.
- Fill with the jerry can and its safety nozzle. On the XL, the nozzle stops automatically at the MAX mark.
- Wipe any spill immediately with a dry cloth, then a damp one, and let it dry fully before lighting.
- Light with the lighting rod, never a match held over the slot.
Store fuel in its original bottle or the supplied jerry can, away from the appliance, and never move the burner while it is lit. Keep children away and never leave the fire unattended.
Will my NYC co-op or condo allow it?
Often, yes, but ask first and ask in writing. An ethanol burner is not a gas appliance, so the NYC Fuel Gas Code prohibition on vent-free gas does not apply to it. What matters is your building. Most co-op and condo boards treat an open flame as an alteration they want to see, and some have house rules against it.
What helps get a yes: the model's UL 1370 listing, the EcoSmart spec sheet showing the minimum room volume against your actual room, the installation details for the box and top tray, and a plan for fuel storage. EcoSmart's own compliance guidance notes that storing more than 5 gallons indoors can trigger a permit requirement under typical fire codes, and the NYC Fire Code regulates flammable liquids in residences, so keep only a modest supply on hand. Your insurer may have its own limits. Our NYC fireplace code guide covers the wider rules by fuel type. If the board says no, a water vapor fireplace is the closest look without a flame.
From our install team
Managing agents in Manhattan respond better to a one page submission than a stack of brochures. We put the UL listing, the room volume calculation and the box drawing on one sheet. It answers the three questions every board asks: is it certified, is the room big enough, and what touches the wall.
Our recommended models
We picked these from the EcoSmart burners and fireboxes we sell and install most, labeled by the job each one does best.
Which should you choose?
Choose an XL burner if:
- Your opening or box is wider than it is tall.
- You want a modern, linear flame in plaster, stone or millwork.
- Long burn per fill matters more than maximum heat.
Choose a square burner (AB3, BK5, AB8) if:
- You have a traditional firebox or want logs on a grate.
- The space is small (AB3) or you want the most heat (AB8).
- It is going in a fire table or a compact niche.
Choose a grate, Heritage or Flex if:
- You have an existing masonry fireplace (grate).
- You want a finished traditional box with glass (Heritage).
- You are building a new wall and want zero clearance (Flex).
Our recommendation: measure the inside of the box and the room, then pick the largest burner that clears both. For most Manhattan and Brooklyn living rooms with a 40 to 47 inch opening, that is the XL700, or the Grate 36 if you are reusing a masonry hearth. Go smaller before you go bigger. An AB8 in a room that is too small is the one choice we talk people out of every season.
Frequently asked questions
What is the difference between EcoSmart XL, AB and BK burners?
XL burners are linear (19.7 to 47.2 inches long) for modern openings. AB burners are square, with the compact AB3 at 5,800 BTU and the high output AB8 at 20,433 BTU. The BK5 is a mid size square burner at 13,000 BTU and powers the Heritage inserts.
How long does an EcoSmart XL700 burn on a full tank?
EcoSmart rates the XL700 at 9 to 12 hours on its 1.8 gallon tank. At full flame it uses up to 0.18 gallons an hour; turning the flame down or using the baffles extends the fill.
How much e-NRG fuel does an ethanol burner use per hour?
At full flame, from 0.08 gallons an hour (AB3) to 0.29 gallons an hour (AB8). In quarts that is about a third of a quart to just over one quart an hour. The XL500 uses about half a quart an hour.
What size ethanol burner do I need for a 42 inch fireplace opening?
If the inside of the box is 42 inches wide, the XL700. EcoSmart's offsets require 5.9 inches on each side of an XL burner, so the 27.6 inch XL700 needs about 39.4 inches and the XL900 needs about 47.5 inches. For a masonry hearth, the Grate 36 holds an XL700.
What is an EcoSmart Flex firebox and do I still need a burner?
Flex is EcoSmart's zero clearance steel firebox in single sided, double sided, corner, peninsula, bay, island and bench formats. The burner comes configured with it, for example an XL900 or an XL500 in the Flex 50SS, so you do not buy one separately.
Can I use any bioethanol in an EcoSmart burner or only e-NRG?
EcoSmart's safety instructions say its burners use only e-NRG bioethanol. Other fuels differ in purity and additives and can give a weaker flame. Never use gel fuel, gasoline or hardware store alcohol.
Do EcoSmart ethanol burners need a vent or chimney?
No. They need no flue, gas or electrical connection. They do need EcoSmart's top tray indoors, a non-combustible surround, 59 inches of clearance to curtains and anything that moves, and a room at least as large as the model's minimum volume.
How much does it cost per hour to run an ethanol fireplace?
Multiply the burner's hourly fuel use by your price per quart. At full flame an AB3 uses about 0.32 quarts an hour, an XL700 about 0.72 and an AB8 about 1.16. Running the flame lower cuts that.
Talk to a specialist
Send us your opening size. We will match the burner.
We have been designing, selling, installing and servicing fire features and outdoor kitchens for over 30 years across New York City, Long Island, Westchester, New Jersey and South Florida. We spec EcoSmart burners, build the boxes and help you through the board submission.
Book a free consultationCall 718-326-4328Showroom: 58-30 Maspeth Ave, Maspeth, Queens.
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Written by the NYC Fireplaces & Outdoor Kitchens team. Last reviewed October 2026. We sell, install and service the products discussed here.
Sources:EcoSmart Fire AB3, AB8, BK5, XL500, XL700, XL900, XL1200, EcoSmart clearances and installation, EcoSmart safety instructions, filling the XL burner, AB8 efficiency ring, e-NRG fuel performance, Flex 50SS, Heritage 42SS, EcoSmart regulations and compliance guide. Specifications change; always confirm with the manufacturer's current installation manual.