What Do Efficiency Ratings Mean, Anyway?

Whether you’re comparing wood, gas, or pellet-fuel appliances, you’ll see an efficiency rating listed in the product information. Between uncertain fuel costs and increasingly strict air quality regulations, more and more consumers are looking for the most efficient heaters they can find. But what do those ratings mean? How are they measured?

The bad news is that there isn’t one standard rating system used by manufacturers, nor are they required to tell you which system they’re using. The good news is that by learning a bit about what the ratings mean, you can put manufacturer claims in context and compare apples to apples when buying a stove or fireplace.

What does “efficiency” actually mean?

In the simplest terms, the efficiency rating on an appliance tells you how much of your fuel will become usable heat in your home. A pound of wood, gas, or pellets contains a certain amount of potential energy; some of this energy will be used in starting and sustaining combustion, some of it will go up the chimney (carrying away particulates and other undesirable byproducts of combustion), and the rest will come out into your home as heat.

Wood Heat: EPA vs. Real-World Performance

Wood stoves and inserts are sometimes advertised with two efficiency ratings: EPA and cordwood/real world performance. EPA testing procedures are focused mostly on particulate emissions, and are very highly standardized. These tests use milled lumber (often pine), precisely stacked, with the stove draft set to its lowest (and smokiest) setting; this is also referred to as a “crib wood” test. While this is useful for determining how much air pollution a stove will generate, it has very little to do with how efficiently your stove will convert firewood into usable heat in your home. Many companies choose to do their own testing with cord wood (usually hardwood) and realistic venting setups, in order to give their customers a more accurate idea of stove performance. Unfortunately, there’s no requirement that companies tell you which efficiency rating they’re listing. For environmental impact, focus on the emissions listing (gm/hr of particulates released into the atmosphere) rather than the listed efficiency rating. For real-world efficiency, a good rule of thumb is that 67%-75% is a good range for quality non-catalytic stoves, with catalytic stoves occupying the 75%-83% range.

(Note: just to make this even more confusing, the EPA is currently in the process of revising its compliance and listing standards. While this process is ongoing, look for “cordwood/HHV/actual measured efficiency (CSA)” in your stove literature.)

Gas Heat: Steady-State vs. AFUE/EnerGuide

Gas stoves, inserts, and fireplaces are rated in two different ways. The Steady State efficiency rating, which offers a higher and more impressive number, is taken only once, after the appliance is fully heated up and burning steadily. While this number is technically accurate, it has very little to do with how your stove will perform over the course of its lifetime, and under real-world conditions. We prefer to work with vendors who list the EnerGuide, P4, or AFUE (annual fuel usage estimate) ratings. These efficiency readings reflect performance over the entire burn cycle, from ignition to cool-down, and use realistic venting setups. If you’re looking at efficiency ratings, and seeing numbers in the high 80% range, you’re probably looking at the steady-state efficiency of the fireplace. The more honest EnerGuide, P4, and AFUE rating systems give numbers ranging from around 60%-70%. A 65% efficiency rating is actually quite good, and an 85% rating, although it sounds much better, probably doesn’t reflect an actual increase in real-world efficiency or performance.

To sum up: efficiency ratings can be confusing, and don’t always give a complete picture of how an appliance will perform in your home. However, with a little bit of time and research, you can put those numbers in context when comparing different products, and make a more informed decision about which stove, fireplace, or fireplace insert will be the best fit for you!


Awnings & Canopies

Often, the sunny patio or deck that’s so perfect for during the fall and spring gets so hot during the summer that it’s impossible to enjoy.  An awning or canopy provides a cool, shaded area, perfect for children & pets, and the ideal place to enjoy a summer barbecue.  A retractable awning extends your home’s usable living space, complements an outdoor kitchen or grilling area, and can increase the value of your home.

girls+dogsThe sun’s rays are strongest between 10 a.m. and 2 p.m., and children and pets are particularly susceptible to sunburn and/or dehydration.  A shaded outdoor area remains cool and helps keep home residents safe from the damaging UV rays of the sun.  The kids can play with the dog while you weed the garden, and afterwards you can all enjoy the view together in comfort.
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Why is Wood So Green?

What’s so eco-friendly about heating with wood, anyway?

Firewood is a renewable resource, and sustainable harvesting practices allow woodlot owners to balance high yield with long-term growth.  Harvesting wood responsibly involves clearing naturally-fallen wood before new growth (intermediate thinning), planting new trees to replace harvested ones, and maintaining a variety of tree species in each lot (biodiversity). When practiced responsibly and sustainably, wood harvesting maintains the natural balance of a forest’s ecosystem, rather than drastically altering or destroying it, as happens with most fossil-fuel extraction and processing.

Carbon cycle ICC-RSF

Photo courtesy of ICC-RSF

Complete combustion of firewood (well-seasoned, and burned in a high-efficiency appliance) produces only carbon dioxide and water; this carbon dioxide is the same amount as would be released during the tree’s natural decomposition process, making wood an almost carbon-neutral source of fuel.  “Almost,” because complete combustion happens only under specific conditions, which are very difficult to replicate in a home fireplace with variable firewood (the wood may be too wet, or the draft may be poor, or some other condition may be preventing complete combustion).  Therefore, most home wood-burning appliances will produce some quantity of carbon monoxide, hydrocarbons, and other emissions.  However, today’s modern, EPA-rated wood-burning appliances release very few emissions (many under 3 gm/hr) into the atmosphere, making them far cleaner than fossil fuels.  By replacing even part of our monthly gas or electric heating with wood heat, we can reduce our greenhouse gas emissions and dependence on non-renewable resources such as oil and coal.

For further information, check out the EPA’s BurnWise program.