Only eight percent of U.S. homes use oil heat today. Natural gas is both cheaper and has lower carbon emissions than oil, though it is still a fossil fuel and its green-friendliness is overstated. Most eco-advocates would rather see a shift to truly renewable heating sources like geothermal or solar. (Thinkstock)

Natural gas has been a more affordable heat source than oil for Americans in recent years. The federal Energy Information Administration (EIA) reports that the average American homeowner will pay only about $732 to heat their home with gas this winter season (October 1 through March 31) versus a whopping $2,535 for oil heat. While the price of natural gas has remained relatively stable in the last few years, oil prices have been high and rising thanks in large part to continued unrest in Middle Eastern oil producing countries. Just two years ago the average winter home oil heating bill was $1,752.

While oil prices are likely to remain high and volatile in the foreseeable future, most energy analysts agree that pricing for natural gas, much of which is still derived domestically, is not expected to rise or fluctuate substantially in the U.S. any time soon. According to EIA economist and forecaster Neil Gamson, the U.S. already has a glut of natural gas and expects even more domestic production to come online soon as drillers are set to open up the Marcellus Shale in Pennsylvania and New York to more gas development.

Only about eight percent of U.S. homes are on oil heat today. Most are in the Northeastern U.S. and were built back in the day when oil was the cheapest way to keep toasty through the long winters. Many utilities have since put gas lines into neighborhoods that didn’t have them in the past, opening the door for homeowners to switch out old inefficient oil furnaces for more efficient gas units.

The federal government’s 30 percent tax credit (capped at $500) for upgrading to a high efficiency furnace expires at the end of 2011 but will likely be extended in one form or another into 2012. In the meantime, some states, municipalities and utilities offer their own incentives and low-interest loans on upgraded, high-efficiency furnaces. Check what’s available in your area via a zip code or map-based search online at the website of the Database of State Incentives for Renewables and Efficiency (DSIRE). Regardless of incentives, gas furnaces tend to cost less than their oil counterparts anyway, but installing one from scratch will incur an extra thousand dollars or two to run a gas line to it from the street. If natural gas continues to be substantially cheaper than oil, the fuel cost savings alone would pay back the up-front equipment and infrastructure investment within five years in most cases.

Environmentally speaking, gas has lower carbon emissions than oil, but hydraulic fracturing (“fracking”)—the highly controversial gas extraction method increasingly employed today (drillers inject water, sand and chemicals at high pressure underground to break through rock and access the natural gas)—takes a heavy toll on surrounding ecosystems and regional water quality. Most environmental advocates would rather see people transition to truly renewable heating sources like geothermal or solar. If you’re going to the cost and trouble of switching out an oil furnace for something new, a geothermal heat pump may cost more ($7,500 and up) than a new gas heating system but will save big bucks and emissions in the long run. For those in reliably sunny areas, a solar heating system will cost even more up front but can deliver similar long term economic and environmental benefits.

CONTACTS: EIA, www.eia.gov; DSIRE, www.dsireusa.org.

With college costs on the rise, it’s hard for students to stay on a budget and survive living on their own. Your first apartment can be cold, damp and drafty, and if you’re a student in Boston, your heating costs may take a big bite out of your monthly budget. Electricity costs money, but If you plan ahead, you can use that extra cash towards your books, entertainment and late night food runs.

One gadget that might help is a draft guard under your door to help keep your warm air in and the cold air out.

Made from the same foam used to insulate pipes in Northern Canada, the Twin Draft Guard keeps the internal climate from being affected by the outside elements allowing for more efficient temperature regulation, and it can save you 20 percent on your energy bill. It’s a simple, cost-effective way to reduce heating costs this winter and put some extra money in your wallet to enjoy college life. It’s also great for blocking out those noisy parties that your roommate decides to throw the night before your big exam.

The Twin Draft Guard is easy to install, stays in place and fits windows and doors up to 36 inches. All you have to do is cut the inserts to the length you need, insert them into the cover then slide the Twin Draft Guard under the door. Doors open and close easily as it glides over all floor surfaces, even carpet. The Twin Draft Guard retails for $9.99 and is available at Lowes, Walmart, Target, Bed Bath & Beyond, Walgreens, or online.

Image courtesy Enertia Building Systems.

Enertia is a brand name for homes designed and sold in kits by North Carolina-based Enertia Building Systems (EBS). The idea essentially marries the concepts of geothermal and passive solar heating/cooling into what amounts to a highly energy efficient hybrid system. Architectural inventor Michael Sykes coined the term “Enertia” in the 1980s to describe the innovative homes he was designing that would store solar and geothermal energy and make use of it for most if not all heating and cooling needs.

Under such a system, solid wood walls replace siding, framing, insulation and paneling, while an air flow channel”"or “envelope””"runs around the building inside the walls, creating what Sykes terms a miniature biosphere. Inside the envelope, solar heated air circulates, pumping and boosting geothermal energy from beneath the house and storing it within the wood mass of the walls, where it is doled out gradually.

By harnessing the properties of thermal inertia”"the ability of materials to store heat and give it off slowly”"an “Enertia” house maintains a relatively fixed and comfortable temperature throughout the warmer day (when solar heat is collected and stored) and cooler night (when the wood walls give off heat to keep things toasty as the mercury dips).

The heart of the system is a south-facing sun space within the envelope that is dominated by windows and which therefore soaks up lots of solar energy, filling the house’s wood walls with thermal energy that in turn radiates into the primary living space. The entire house functions like an electric heat pump”"moving warm and cool air around to accommodate the comfort needs of the occupants. It works even throughout the seasonal changes of the year”"with minimal to no fossil fuels consumed or pollution generated.

In one Enertia house in North Carolina, the only power bill the owners typically pay is $35/month for electricity. They also have a back-up in-floor radiant heating system powered by natural gas for long cloudy stretches or unusually cold weather. Gas bills for heat typically total $150 for the year, meaning the owners’ total annual outlay for heating, cooling and electricity is less than $600″"some $1,000 less than traditional homes in the same zip code are paying, according to data from the U.S. Department of Energy.

EBS markets several different designs for its Enertia houses, but all share the basic premise of primary interior living space heated and cooled by air channeled in from a south-facing “buffer zone” envelope and from below grade. Smaller houses in the line top out at about 2,000 square feet over two floors of living space, while larger ones encompass some 4,000 square feet of living space over three floors. Depending on the model, you could spend anywhere from $66,000 to $292,000 for a complete plan and building materials kit. The rest”"including the selection and cost of the land and the labor to build the house”"is up to you.