Escalating summer peaks turn United Power into load warrior

United Power's headquarters in Brighton, Colo., enjoys year-round comfort and energy savings because it is heated and cooled with 35 all-electric geothermal heat pumps. (Photo by United Power)

Colorado's Front Range has become a land of summer peaks where air conditioners are the nemesis, and United Power has chosen the heat pump as its weapon.

The Brighton-based cooperative went from serving 20,000 meters in 1990 to almost 65,000 meters in 2008.  As the new houses went up, air conditioners went into them—45 percent of the region's homes are now air-conditioned, compared to only 13 percent 15 years ago.

The problem is that most of those air conditioners operate only from 2 to 9 p.m. from June to September, when residential demand is at its highest and peaking natural gas power at its most expensive. "That makes air conditioning in Colorado a lousy load no matter how efficient the unit is," explained United Power Member Services Specialist Ed Maycumber.

Rebate program to the rescue

To combat the spiky load curve, United Power offers customers generous rebates on energy-efficient electric appliances and systems. Chief among those systems are heat pumps, both air-source (ASHP) and geothermal (GHP). Maycumber gave a presentation (1 MB PPT) on United Power's rebate program at the Geothermal Technologies workshop in June. "These systems save our customers money on their electric bills, but we don't give out rebates because we are nice guys," said Maycumber. "We're doing it to shave the peaks and fill the valleys."

The co-op pays $400 for the installation of ASHPs, and $2,500 for GHPs. Tri-State Generation and Transmission Association, United Power's wholesaler, offers an additional $150 per ton. Energy-efficient, electric water heaters, the second highest energy consumer in the home, qualify for multiple rebates.

Heat pumps for cooling

The ASHPs are United Power's most popular rebate because they are less expensive and easier to install than GHPs. The systems are coupled with forced-air gas furnaces and can also be used for both heating and cooling, unlike an air conditioner. The SEER efficiency of an Energy Star-rated air conditioner and ASHP is the same, so why does United Power offer a rebate? "If customers use the heat pump the way it is meant to be used, it helps us fill valleys in the winter," Maycumber explained.

On the Front Range of Colorado, 55 percent of all heating demand occurs when temperatures are 42° or warmer. Over 40°, ASHPs heat more efficiently than gas furnaces, relieving the demand for natural gas generation during peak hours. In spring and fall, the all-electric units allow homeowners to take advantage of United Power's off-peak rates, even as they increase the utility's electricity sales. "Running an air source heat pump instead of a natural gas furnace at 40 degrees and warmer can save from $25 to $50 per month—and more compared to propane—on overall heating costs," said Maycumber.

Pushed by rising natural gas prices, customers who installed ASHPs are increasingly relying on them for heating. "Before 2003, maybe 1 percent of the ASHPs were being used to heat homes. As natural gas prices rose regionally, customers started calling, wanting to know how to switch the heat pumps to be their primary heat source," Maycumber recalled. "Now, about one third of the units are running most of the year."

Geothermal best load

No air-source heat pump can match the performance of its geothermal counterpart, however; Maycumber is quick to point out. "Depending on the model, a ground-coupled heat pump will cool for one third the cost of an ASHP or AC unit," he said. "And it will heat for half the cost of a natural gas furnace, and even less on off-peak rates."

While “cycling” ASHPs and air conditioners can only shave peaks, cycled GHPs can both shave peaks and fill valleys.  A GHP-conditioned home uses twice as much electricity (mostly off-peak) as a home with a natural gas furnace. "Overall, it is just a better load factor," Maycumber declared.

The units are a good load match for renewable energy, too, he observed. "Peak summer solar generation occurs between 10 a.m. and 4 p.m. The wind primarily blows at night during winter, spring and fall in Colorado—diminished periods or no peak demand," Maycumber said. "GHPs can run 24/7/365, so the units give us a place to use renewable generation."

Partnerships, marketing for success

United Power has offered a GHP incentive program since 1985, and the experience has taught a few lessons. Acting early on as the installer/contractor, for example, proved not to be the best model for this utility. "Local contractors saw the co-op as competition," said Maycumber, "especially the propane and natural gas furnace vendors."

Working with contractors is a better way to promote a rebate program and to increase industry awareness about the technology. Building trade allies ultimately improves the customer's satisfaction with the system.

Keeping the customer's perspective in mind is critical to effectively marketing a system. "You have to communicate that a GHP doesn't cost the homeowner money—it saves it," said Maycumber.

Increasingly, customers are concerned about the environment, he added, and GHPs address 58 percent of a household's carbon footprint: heating, cooling and hot water. The system is available any time of day in any weather, and it is 300 to 500 percent efficient. Compare that to a home photovoltaic system, which generates only 6 hours per day and is 13 to 17 percent efficient. The cost of a 5-kW PV system is about $37,000, versus $20,000 to $30,000 for the equivalent kilowatts in a GHP. "That makes the heat pump a better investment from both the environmental and economic standpoint," Maycumber insisted.

Energy savings, safety for public buildings

United Power is such an advocate of geothermal heat pumps that it installed 35 of them in its new headquarters, opened in 2006. Combined with measures such as energy-efficient lighting and daylight harvesting, the system reduces the facility's energy use by about 14 percent over the old building, which was a little more than half the square footage.

As a bonus, the co-op has one of the coolest, quietest boiler rooms around, since there is no boiler. "It's much safer for maintenance crews," Maycumber noted.

Municipal facilities and buildings that house public agencies are ideal candidates for geothermal heat pumps, in Maycumber's opinion. Such organizations will stay in the building long enough to recover installation costs. "They also have a responsibility to keep operating costs low for taxpayers, which justifies the initial investment," he said.

Maycumber has worked with county and city governments in United Power's service territory to persuade them to install heat pumps in new buildings. Some officials have toured United Power headquarters, but it is an uphill battle, he admits. "Some mechanical engineers and contractors are stuck in their old ways and argue against the technology. And it's still hard to get people to look beyond the first cost," Maycumber said.

That won't stop United Power from continuing the fight. "It's all about load control," Maycumber stated, "and heat pumps represent our best opportunity, and the customers' best investment."

Resources

United Power

Exploring New Energy Strategies for United Power's Customers (1MB PPT)

Tri-State Generation and Transmission Association

People

Ed Maycumber

Related articles

Energy Services Bulletin, June 2008
Geothermal workshops to focus on technologies

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