Buyer’s guide to pellet- and wood-burning stoves

Rising energy costs have prodded Americans to buy not only more fuel-efficient cars but also more firewood and wood pellets, which generally are made from sawdust and wood shavings, as fuel to heat their homes. More than 800,000 homeowners are already using wood pellets.

Although you can use pellets (shown) to run a whole-house heating system, the fuel is more commonly used to feed fireplace inserts and freestanding stoves serving as supplemental heating appliances. Turn on an insert or stove when you're in a room and you can turn down the household thermostat and thus save money. Converting wood waste (and other biomass, like shelled corn and wheat hulls) into energy-dense fuel results in less waste being heaped onto landfills. Plus, pelletized wood and more-traditional solid wood are eco-friendly alternatives to nonrenewable fossil fuels such as natural gas, oil, and coal.

Before you jump on the wood-burning bandwagon, though, consider a few of the drawbacks. Because most homes aren't equipped with a thermostat in every room, the heat from an insert or stove might cause nearby thermostats to think the temperature throughout their zones is at the set level. The result? Rooms adjacent to the heated space could become cold, and you might be tempted to boost the thermostat when in those rooms. That defeats the purpose of the stove or insert, because it will save you money only if you keep the thermostat turned down.

Also, your actual savings depend on fuel costs in your area. It's also worth noting that wood and wood pellets don't burn quite as cleanly as natural gas or fuel oil, which is an environmental issue and a concern if you or family members have respiratory difficulties. Perhaps most important to note is that wood-burning and pellet-burning appliances require constant attention—loading, lighting, tending, and cleaning—especially compared with the "just press start" ease of most gas- and oil-powered appliances.

How to Choose
Appliance type. If you already have a fireplace, don't use it for space heating. Fireplaces often cause all areas except the room they're in to become cold. And their efficiency is very low—generally about 25 percent. But you can boost the efficiency of a fireplace with a fireplace insert. Essentially a self-contained firebox, the insert fits into the existing box and allows air to circulate around it, thus heating it. The insert is connected to the chimney to vent the smoke and combustion by-products. If you don't have a working fireplace, choose a freestanding stove, which you can place nearly anywhere in your home. (Venting a freestanding stove requires punching through the building envelope and installing a chimney of appropriate design, or alternatively, using an aftermarket power vent designed for wood-burning appliances.) Whichever type of appliance you choose, expect to pay at least $750 plus installation fees of $250 and up. Use a National Fireplace Institute-certified installer.

Heating needs. Heat load is measured in British thermal units per hour, or Btu/h. You need 25 to 30 Btu/h per square foot, or at least 5,000 Btu/h for a 200-square-foot space. The actual heat loss (and conversely the amount of heat needed) is based on where you live (outdoor air temperature), the amount of insulation in the ceiling and exterior walls of the space, the number and size of the space's windows, and whether or not there is heated space above and below the room. Calculate how many Btu/h you need to heat your space and select an appropriately sized insert or stove.

Fuel. The average cost of a cord of firewood or a ton of wood pellets is $190, according to the United States Department of Energy. But for a true comparison of the costs, you have to look at not just the price of the fuel but also the heating value of the fuel, also measured in Btu, and the efficiency of the heating appliance. Using averages for all three, the Energy Information Administration's Heating Fuel Comparison Calculator estimates it costs $14.39 to produce 1 million Btu using pellets or solid wood. Those figures are between the costs of coal ($5.35) and natural gas ($17.82) and are well below the costs of oil ($22.83), propane ($27.65), and electric furnaces ($32.49) and electric baseboards and space heaters ($30.86).

Other significant differences between wood and pellets:
Availability. Cord wood is sold in most parts of the United States. If you're lucky, you might be able to harvest the fuel for free from your own property. Wood pellets aren't as widely available, though manufacturers are in every region of the country. When buying cord wood, be sure you get what you pay for. A true cord is a stack that's 8 feet long x 4 feet deep x 4 feet high; a "cord run" is the same length and height but includes only 16-inch logs, making it a third the volume of a true cord.

Grade. Use whatever hardwood is plentiful in your area and prepare and store it properly. There are two types of wood pellets: standard grade, which contain more ash, and premium grade, which burn a bit cleaner but are a bit more expensive. Some stoves can burn both grades and others are designed to burn pellets made of corn, wheat, and other materials. "Multifuel" inserts and stoves can burn pellets made from wood and wood alternatives.

Emissions. Traditional wood-burning fireplaces and older stoves can be woefully inefficient, and are known to produce upwards of 40 grams of smoke per hour. The latest wood-burning inserts and stoves are much better—EPA-certified to produce no more than 7.5 grams of smoke per hour. Pellet emissions are so minimal that the EPA does not regulate them (though voluntary certification is available). In areas of the country where burning solid wood is restricted, pellet burning is often unrestricted.

Convenience. Wood-burning appliances are literally "off the grid," so you need to load, light, and stoke them by hand. Pellet-burning devices, on the other hand, can be fully automated but require electricity to operate. (Battery backups are available, and you can also connect the units to a backup generator. Although you don't need to tend to pellet appliances, you must fill the hopper frequently (shown), depending on the size of the reservoir and amount of use. You'll need to dedicate sufficient space to store wood (an average of 6.5 cords to heat a home for one heating season—obviously less to fuel a single supplemental heating appliance) or premium wood pellets (7.3 tons) according to the USDA's Fuel Calculator.

Regardless of what you burn, you'll have to clear out the ashes, clean the chimney, vent connector, and flueways, and perform basic maintenance. Also have the unit inspected annually by a Chimney Safety Institute of America-certified contractor.

Safety. Burning solid wood produces sparks, shifting embers, and creosote, a flammable liquid that can accumulate in and clog vents and chimney stacks. Wood can also ferry things like mold and mildew into the home, and stacked cords can shelter spiders, termites, insects, and even rodents. There's also the risk of fire and carbon-monoxide poisoning, so be sure to install and regularly test smoke and carbon-monoxide alarms. If you're felling trees and cutting wood with a chain saw, there are additional safety concerns.

Design considerations. Unlike boilers and furnaces, fireplace inserts and freestanding stoves often occupy public spaces of the home and might be the focal point of the room, which means they're made to be seen. They're available in a variety of styles and finishes—classic cast-iron potbellies and contemporary stainless-steel models—to match any décor. You'll get a sense of the options at the Web sites of the manufacturers below as well as at the Hearth, Patio & Barbecue Association Web site:

Appalachian Stove
Avalon
Blaze King
Breckwell Hearth Products
DESA Heating Products
England’s Stove Works
Energy King
Harman Stove Company
Kozy Heat Fireplaces
Kuma Stoves
Lennox Hearth Products
Napoleon Fireplaces
NU-TEC Incorporated
Rais
Vogelzang
Wittus

Features That Count
Once you’ve figured out the type of stove and fuel you need and calculated your heat output and style requirements, it’s time to look at specific features. For more information and a convenient checklist that outlines the various options, review the Pellet Fuels Institute’s fact sheet.

Ash pan. The bigger, the better. You won’t have to empty a large catch pan as frequently.

Automatic ignition. This feature, controlled by a thermostat, eliminates the need for matches and starter gel, and allows for hands-free electric start-up of pellet-burning inserts and stoves.

Back-up battery (or portable generator). In case there’s a power outage, this device operates the pellet-burning appliance.

Built-in thermostat. You can control the ambient temperature in the room by regulating the flow of pellets into the burner pot.

Hopper. The larger the reservoir, the longer the appliance can run between pellet refills—that means less work for you.

Viewing window. A wide bay window provides you a better view of the flickering flames.

Comments

[t kroll]

Some might argue that the environmental & social cost of coal or other non-renewables should be figured in as well. That being difficult to get agreement on, it seems one should at least measure the energy needed to produce and deliver the fuel and add that to the efficiency rating.

For instance, how much extra energy does it take to produce wood pellets compared to cordwood? How much energy does cordwood take to cut and deliver? How about coal production and delivery?