With rising energy costs and concerns with the financial market, many home owners are turning to hearth appliances to help save money on heating costs. This guide will help you understand some of the common principles and terms used so that you can make the best decisions for your home and family.

 

 

 

Homeowners choose hearth products based on several factors, with the primary concerns usually being features, efficiency and aesthetics. "Efficiency" is a largely misunderstood term, so we'd like to help you understand how the term is used in the hearth industry so you can make fair comparisons and the best buying decision for your home.

 

Efficiency
Efficiency in hearth appliances is generally applied to determine heat output; BTU input x efficiency = BTU output. A gas appliance with a fuel intake of 20,000 btu's with 80% efficiency provides 16,000 BTU output. Conversely, if a manufacturer provides only the BTU input and the output, you can determine the efficiency by dividing input by the output. Efficiency ratings MAY ONLY BE APPLIED to heater rated appliances; this is why you will not see an efficiency or a btu output rating on a decorative gas appliance such as vented gas logs or vented gas coal baskets.

 

The input rating (fuel consumption rating) of the appliance helps you determine how much fuel is being used by the appliance.

 

A Wood Stove will list the amount of fuel burned the lenth of burn time (ex. 25 lbs of wood for 6 hours). Firewood is generally figured at 8,000 btu's per pound. Wood stove efficiency ratings are harder to truly understand because the fuel is so greatly inconsistent; various types of wood provide varying amounts of heat; the amount of water in the wood greatly affects the amount of usable heat you will net; the venting system greatly affects the operating efficiency. This has made it difficult for the government to establish efficiency ratings on wood stoves, making it harder for manufacturers to provide exact data that consumers can understand and believe. In a nutshell, most wood stoves are rated at 65-75% efficiency range. Rating a wood stove in terms of heat output is further complicated by the fact that the burn rate and btu output of a load of wood varies drastically. If a 25 lb. load of wood is estimated to burn for 6 hours, it may provide 10,000 btu in the first hour, 60,000 btu for 30 minutes in the third hour, 10,000 btu in the last hour. Most manufacturers state btu output as "up to 60,000 btu's" and unless you realize this output is only for perhaps 30 to 60 minutes of the total 8 hour burn time, it's easy to be misled into thinking that the 60,000 btu heat output is a constant number. 8,000 btu's per pound x 25 pounds = 200,000 btu's; divided by 8 hours you're AVERAGING 25,000 btu's per hour.

 

Pellet stoves are designed to burn optimized wood (or other biomass) that's been fuel. Wood pellet fuel averages 8,000 btu per pound and efficiency ranges 75-80% average. By controlling the burn rate in pounds per hour you're able to adjust the amount of heat needed. Pellet stoves require electricity to operate; there is an auger motor that feeds the pellet fuel into the firebox and the venting uses a forced air fan system to evacuate the smoke to the outdoors. Quality of the fuel greatly affects the heating capability of the pellet stove and how cleanly the stove operates. By knowing the cost of a bag of pellets (generally 40 lbs. per bag) you can easily determine hourly cost of operation. Most pellet stoves are going to be set to run at 3 pounds per hour average. Remember, 3 pounds of fuel at 8,000 btu per pound means you're consuming 24,000 btu's of fuel per hour.

 

Gas stoves are easier to decipher efficiency and costs; there are 91,500 btu in a gallon of LP gas. A gas stove or fireplace with an input of 25,000 btu will burn for over 3-1/2 hours on one gallon of gas if the fire is burned continuously. (If the gas appliance is operated by thermostat and the flame cuts down or off based on room temperature, then it will therefore burn for a much longer time per gallon). Natural gas is equivalent, but natural gas is sold by the cubic foot so the math is a little different (see the chart, above left) but the result is the same.

 

 

Electric fireplaces & inserts are limited to 5,000 btu's hourly if the appliance is able to plug in to a wall outlet; there are now many electric fireplaces that can be hard-wired to a 220  circuit and these can provide up to 10,000 btu's per hour. Electric fireplaces are 99% to 100% efficient at turning electricity into heat. So look on your electric bill, find out your cost per kilowatt and it's easy to figure your costs of operation. Currently in most areas, costs average 8 cents per hour to operate the 5,000 btu electric models on high heat.

 

Some hearth products are classified as "decorative" and some are classified as "heaters". When an appliance is tested and the company applies for safety approvals, the appliance must meet certain efficiencies to gain the more stringent "heater" classification. A heater-rated appliance may certainly also be "decorative" in terms of being attractive, but a heater rated appliance has gained recognition as meeting the higher efficiency requirements of this classification.

 

Once you know how the math works, you can see what a drastic difference there is in a decorative gas appliance versus a heater rated appliance. Let's say the cost of LP gas is $3/gallon to make the math easier.

By understanding a bit more about hearth appliances and their efficiencies, it's easier to make an informed decision about operating costs.