What is ‘Green’ Heating?

If the country is serious about renewable energy, it means getting a lot more serious about all renewable heating options.
By John Ackerly | May 19, 2016

“Green heat” is part of the name of our organization: the Alliance for Green Heat.  But the definition of “green” is getting less clear when it comes to heating and to renewable energy generally.

Tesla is releasing an affordable electric car with great fanfare, and it’s alarming how many people aren’t thinking about which grid they will be recharging the car on.  There is nothing “green” about an electric car that uses electricity on the grid in scores of states where coal still dominates the fuel mix.

Less in the spotlight is the electrification of heating and the new popularity of high-efficiency,
air-source heat pumps.  Air-source heat pumps are gaining traction as a green solution because they remove combustion from the home and provide high-efficiency electric heating and cooling.

Both heat pumps and electric cars remove combustion from the appliance and centralize it in gas, coal or nuclear power plants, unless you have a very large array of solar panels, or the grid of your state has a lot of hydro or nonhydro renewables. 

In Washington state, three-quarters of the electricity on the grid comes from renewables (mostly hydro, but wind is starting to make up a significant share).  In California, about 30 percent of electricity comes from renewables. More than 50 percent of electricity comes from renewables in six states: Vermont (99 percent), Washington (75 percent), South Dakota (75 percent), Idaho (74 percent), Oregon (68 percent) and Maine (66 percent). 

At least three of these states are now offering incentives for electric heat in the form of high-efficiency, air-source heat pumps.  An Oregon utility offers a rebate to switch from wood to a heat pump.  The problem with electricity has been its cost, not necessarily its carbon intensity, but as more cars, heat and other uses rely on electricity, there will be some major drawbacks.  Peak electricity loads will be shifted to the winter, not just summer months. And meeting more peak load periods typically involves higher carbon-dense fuels.

A key problem with electric heat, which involves all heat pumps, is that one has already wasted 65 to 75 percent of the fuel, whether it was coal, gas or wood chips.  Power plants in the U.S. rarely use their waste heat, which is the majority of energy produced.  By decentralizing the combustion and focusing on distributed energy technologies such as pellet stove or boilers, we capture 70 to 80 percent.

This brings a huge contradiction in the renewable energy movement.  Many think we are and should move to distributed, local production of energy, which includes rooftop solar, pellet stoves and boilers, etc. But we are also moving more toward the continued centralization of energy supply, which includes large-scale wind farms, large-scale hydro, and nuclear.

So what is “green heat?”  First of all, the greenest Btu is the Btu you never use.  For anyone interested in green energy, the first step is to get a home energy audit and make sure your house is not leaking like a sieve. When you have an energy audit, find a BPI-certified auditor and make sure they use Annex J, the Alternate Procedure for Solid Fuel Burning Appliance Inspection, to inspect your wood or pellet stove.

If you are part of the 33 percent of the U.S. population who already use electric heat, you can pay a bit more to your utility and buy green power.  Not all utilities offer this option, but for my home in Maryland, it adds less than 10 percent to our monthly electric bill.

Geothermal, or ground-source heat pumps, draw heat from the ground but use a lot of electricity in the process. Again, for geothermal to be considered truly green, you should be using electricity generated from renewable energy to pump the heat into your home.  Otherwise, geothermal is little more than high-efficiency electric heat.

Solar thermal is somewhat of a misnomer because solar thermal systems rarely provide energy for space heating.  In the U.S., they usually only produce enough heat to cover domestic hot water needs, and most people do not use enough domestic hot water to make the investment worthwhile.

How about wood and pellet stoves?  Are they really “green?” I often get baffled looks from my friends and neighbors when I talk about wood heating.  They say, “Doesn’t the smoke make it less than green?” My answer is always yes.  If there is visible smoke, you either don’t have an EPA-certified stove, are using green wood, aren’t operating the stove well, or all of the above. Putting a steady stream of smoke into a neighborhood can hardly be considered green, even though you could argue that wood still has plenty of environmental benefits compared to gas or oil.

In fact, none of the last three EPA-certified stoves I have used to heat my house can burn dry wood without visible smoke at their lowest air setting. Although they can work well with plenty of airflow, these stoves are made in a way that lets people use them poorly. Ironically, the main reason many manufacturers make stoves with such low air settings is because the EPA mandates it. This is surely one of the most counterproductive EPA requirements.

Pellet stoves are consistently superior to wood stoves when it comes to reducing smoke. A German-designed pellet stove in the 2016 Pellet Stove Design Challenge was so clean that you could barely see the particulate matter catch on the white filter. 

Pellet stoves that emit under 1 gram of particulate matter per hour are a great “green” heating option for American homes.  We expect to see more and more homes using both pellet stoves and high-efficiency, air-source heat pumps together, as they can complement each other. With better federal and state policies, we could even expect to see double-digit growth of pellet stoves once oil and gas prices start to increase again.

If the country is serious about renewable energy, it means getting a lot more serious about all renewable heating options. The most affordable ones now are pellet stoves, anywhere in the U.S., and high-efficiency heat pumps in states where the majority of electricity comes from renewables. 

Getting serious about renewable heating technologies is happening slowly at the state level, and far more quickly in Europe. In 15 to 30 years, renewable electricity may be cheap and plentiful enough to take over a big chunk of our space heating needs and our cars, but we may be looking at 40 to 60 years to get that much renewable energy on grids.  Perhaps wood and pellet stove and boilers will be more of a transitional low-carbon technology, but for now, they remain a very affordable, smart way to reduce fossil heating fuels. 

But first, get an energy audit.

Author: John Ackerly
President, Alliance for Green Heat