Henry Gifford is a man who designs mechanical systems for very energy efficient, comfortable, and affordable apartment buildings in New York City, along with his partner, architect Chris Benedict. In a recent article in Fine Homebuilding, Henry explained how geothermal heat pumps work in a way that I will always remember. I paraphrase:

Dig a hole in the ground. Put some buckets of water in the hole. If you are deep enough below ground, the temperature of the water in the buckets, after a while, will be about 55⁰F. Take the bucket into your house and put it in your refrigerator. The fridge will cool the water down to say 50⁰F, and the heat produced in the coils behind the refrigerator will add some heat to your house. Voila! You’ve created a geothermal heat pump.

Notice that the heat produced is not free. It takes electricity to run the refrigerator. And if you don’t want to spend your days hauling water in buckets from the hole in the ground to your refrigerator, you’ll want to install a water pump, which uses more electricity.

The very best residential geothermal heat pump system, according to Henry, has a coefficient of performance (COP) of about 3. This means that for every 2 watts of energy the system pulls from the ground, you have to provide only 1 watt of electricity. You get 3 watts out for 1 watt in. But a typical system has a COP of about 2.

Given that electricity is produced at power plants that use fossil fuels, and depending on the mix of fuels your utility uses to produce electricity, you will probably burn more fossil fuels using a geothermal heat pump with a COP of 2 than you would using an efficient gas- or oil-fired furnace. And geothermal heat pumps are much more expensive to install than traditional furnaces.

At Home Energy Magazine, where I work, we always tell people that if you have your house air sealed, insulated, and provided with the right amount of ventilation to keep you healthy, you can do better with a medium-efficiency furnace than you would with a high-end system—ike a high efficiency gas furnace—and a leaky house. For most of us, that’s the best choice of all, for heating and for cooling.

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A Closer Look at Geothermal Heat Pumps

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Is the Hydrogen Highway a Good Idea Again?

Can growing marijuana change the way homes use electricity? In rural Humboldt County, in far-northern California, there’s no doubt that it can. Figure 1 tracks average monthly residential electricity use in Humboldt County and in California. Until the mid-1990s, these two values were almost identical. But after 1996, Humboldt County’s electricity use suddenly turned upward. What happened? In 1996, California voters passed Proposition 215, which legalized the medical use of marijuana. In practice, Proposition 215 enabled almost anyone to purchase marijuana. Humboldt County supplied much of the upsurge in demand. Marijuana is a hardy plant and grows just fine outdoors, but many farmers grow it indoors to protect themselves from nosy neighbors, police, and gangs. It’s a true cottage industry.
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Figure 1. After 1996, Humboldt County’s per capita electricity use suddenly turned upward. What happened? (Image credit: California Energy Conservation, U.S. Census)

Two researchers at Humboldt State University, Peter Lehman and Peter Alstone, have documented the energy and environmental impacts of marijuana production in the region. Growing marijuana indoors is an electricity-intensive operation, relying on banks of grow lights and industrial-scale ventilation fans. Even a “modest” operation can rack up several thousand kWh per month. Hundreds, if not thousands, of Humboldt County residents supplement their incomes with “grows.” Similar enterprises exist throughout North America. In Colorado, for example, a single raid found grows in 25 Denver basements. The only difference is that in Humboldt County, the electricity impact is visible at a regional level.

Most energy auditors, utility repair staff, and weatherization crews can tell stories about visiting homes where the occupants are growing marijuana or running other drug operations. Sometimes the auditors never get beyond the front door, or perhaps they are told not to enter a certain room, or the “garage” out back. In any event, that’s usually a signal to abort the job and leave the premises.

It is also important to understand the consequences of growing marijuana inside the house. Simply put, cultivating marijuana indoors destroys homes. The plants create water vapor, which encourages highly toxic mold growth and destroys building materials. The larger operations abandon any pretense of living in the house, because they chop holes in walls and floors for ventilation and wiring. These are greenhouses masquerading as homes, and they are not habitable without tens of thousands of dollars of remediation. The police department of Ottawa, Canada, maintains a list of homes where marijuana is grown so that city authorities know which houses are likely to have mold and structural problems. Of course, the house might burn down before the mold does it in, if the huge electrical loads overwhelm the residential wiring, or stolen electricity is brought in the house through amateur wiring.

Without arguing the merits of legalizing marijuana, it is clear that our drug laws have created a new—and large—use of residential electricity. One likely side benefit of decriminalizing marijuana will be reduced home energy use in Humboldt County, in California, and in the rest of North America.

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July/August 2010 Editorial: A Cottage Industry with High Electricity Use

Photo by Jovan Peric – Fotolia.com

Homes with high energy consumption are likely to provide us more opportunities to save energy. If that’s true, then why don’t we see more programs and businesses geared toward the high users?

Regulatory authorities discourage utilities from creating programs targeting the high users. It is politically unpopular for utility programs funded by ratepayers to support the wealthy. High users, the logic goes, are probably wealthy and therefore able to save energy without assistance. The same attitudes prevail at the federal level, as evidenced by the low-income weatherization programs; caps on tax credits; and less emphasis on the frequent causes of high use, such as swimming pools, hot tubs, heaters for water beds, and well pumps. That view is understandable, but if that’s where the cheapest energy savings lie, should this benign neglect be reconsidered?

It’s also important to realize that high users are not necessarily rich. The city of Tallahassee compiled an impressive list of 101 explanations for high summer utility bills. Only a few of them are associated with high-wealth possessions or activities; most are linked to defective equipment or mismanagement. A separate Florida study of 172 representative homes found that the highest user—clocking in at 40,000 kWh/year—was definitely not wealthy; he had a defective air conditioner and a broken timer on the pool pump.

A few communities have already recognized the problem of high energy and water use. For example, Marin County in California, and some mountain towns in Colorado, have enacted stricter energy efficiency codes for McMansions and other oversize homes. These large homes are almost certain to become high users, so the codes effectively target high users. Some utilities have operated under the radar, using bill stuffers as a means of targeting the high users. But these are the exceptions that call attention to the absence of other approaches.

Figure 1. Annual electricity use, in kWh/year, by number of years Seattle City Light customer lived at same address. Source: “Residential Customer Characteristics Survey.” Seattle City Light, February 2010.

High users often pay more for electricity than average users, because a quarter of the nation’s utilities have increasing block tariffs. This gives high users a greater financial incentive to save.

At the same time, we know surprisingly little about the high users. Is their high energy use caused by more heating and cooling? More appliances? Unique appliances? Defective equipment? Less regard to energy costs? Is the low-hanging fruit just a mirage? It seems that some research could go a long way here. A recent survey conducted by Seattle City Light is full of intriguing results and hints at the strange habits of the high users. In Seattle, the longer people occupy a home, the more electricity they use (see Figure 1). Perhaps “appliance accretion” is one cause of higher energy use—that is, once a television gets plugged in, it never gets unplugged. Surely we need to learn more so that we can make energy conservation irresistible to this important group.

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May/June 2010 Editorial: Targeting the High Users

It is the typical, damn worker’s life, the environment, fisherman, animals and surrounding countries and States in the Gulf and drill…drill…drill..$$$$ even though MOST of the deep drilling rigs are owned by BP and those that are not are not prepared (they use the same disaster plan as BP) to handle another blow-out… I guess besides the Judge’s personal investments in the Oil industry… we have a lot of policy makers with OILY POCKETS.