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2001 Solar Demonstration – Homes

Installation Information
Participant Building Characteristics
Participant Recruitment


In 1999 the Montana Legislature approved a Universal System Benefits Charge, or USBC. Under the USBC programs, all NorthWestern Energy customers pay a charge to ensure continued funding for public purposes programs such as energy conservation, renewables and low-income energy assistance. For the typical homeowner, the benefits charge is about $1 per month. USBC funds have helped pay for the installation of renewable energy systems across the state. These systems help lower operating costs for consumers and provide opportunities for people to learn about renewable energy in their own communities.

The 2001 Montana Residential Solar Electric Demonstration Project resulted in the installation of 10 residential photovoltaic systems in the NorthWestern Energy service area in 2001 and one in early 2002. The objectives of the project were to increase the number of solar demonstration projects, to increase public awareness of the benefits of solar energy, to help create an infrastructure for renewable energy in Montana, and to generate electricity from a clean resource.

In order for a homeowner to participate in the program, the homeowner had to submit an application and provide documents from the proposed PV dealer/installer (of their choice) describing the photovoltaic system components and the estimated cost for hardware and installation. NCAT staff reviewed the homeowner application and the dealer/installer documents. The homeowner was informed by telephone of their acceptance into the buy-down program. The homeowner was urged to contact their chosen dealer/installer to get the equipment ordered and shipped as soon as possible. A buy-down, or rebate, of $4,500 was paid directly to the homeowner upon completion of installation, signoff by the local electrical inspector and inspection by NCAT staff.

The original proposal called for installing 15 one-kilowatt systems. From May through September 22 homeowners applied to receive and were selected to be participants, but for various reasons half of them dropped out of the program. Nevertheless, 10 systems were installed in 2001 and one was installed in mid-January 2002; the total capacity of the installed systems is 14.2 kilowatts.

Because the money for 15 systems funded under this year’s program was not fully allocated, the money for the four systems not installed ($18,000) was carried over to the 2002 program. The Residential Solar Electric Demonstration Program in 2002 was proposed to install 15 kW of residential photovoltaic capacity; with the carry-over funds, the 2002 program will fund up to 19 kW of installed capacity for grid-connected, net metered residential photovoltaic systems.

All 11 residential photovoltaic systems were installed in the MPC electric service territory. All of the systems are net metered. Two systems have a battery bank with an automatic transfer switch that isolates the home and provides electricity to selected circuits while the utility grid is down. Of the roughly 20 megawatt-hours (mWh) that are estimated to be produced by the systems over a year’s time, about 8 MWh are expected to be fed into the utility grid and 12 MWh to be directly used by the typical household. These systems are expected to produce electricity at about $0.24 per kWh.

In the previous year’s program, 24 PV systems were installed by one dealer at an average cost of $9.81/Watt. In this year’s program five dealers installed the systems and the costs ranged from $8.16/Watt to $15.48/Watt of installed capacity. The ground-mounted systems (2) installed cost averaged $8.77/Watt; the roof-mounted systems (6) averaged $10.81/Watt; and the pole-mounted systems (3) averaged $11.58/Watt. Significant variables that increased the system cost were pole-mounting the array, trenching for wire burial, adding a tracking system, including back-up battery storage, and the distance of travel for the dealer/installer. The lowest cost ($/Watt) installations were generally ground-mounted. The most expensive system ($/Watt) installed in this year’s program was pole-mounted with two-axis tracking and a back-up battery storage system ($15.48/Watt).


Worldwide demand for photovoltaic products is increasing rapidly, resulting in expanded manufacturing capacity and a corresponding reduction in manufacturing costs. These lower manufacturing costs will reduce hardware prices substantially when a better balance exists between supply and demand. More and more homeowners and building owners have expressed interest in renewable technologies as a means to preserve a greener environment and reduce dependence on depletable resources.

Installation Information

Installation Standards. New interconnection standards, revisions to the National Electrical Code, and testing of inverters to new Underwriters Laboratories’ standards will help alleviate utility concerns about safety, equipment protection, power quality, and reliability of service. The systems installed under this program satisfy the following:

• IEEE P929 interconnection standard, which defines the equipment and functions necessary to ensure compatibility between the PV system and the utility.

• UL 1741 inverter test standard, which deals with safety issues of grid-tied PV inverters, addressing electric shock hazard, fire hazard and utility compatibility. A utility-interactive inverter that passes UL 1741 will be a non-islanding inverter and satisfy the interconnection requirements of IEEE P929.

• The 1999 National Electrical Code, which requires all utility-interactive PV systems to use listed inverters that pass UL 1741. In effect, any small utility-interactive PV system in compliance with the 1999 NEC will automatically be in compliance with IEEE P929.

Site Selection. All NorthWestern Energy residential customers were eligible to participate. However, each applicant was required to complete a site assessment form to ensure that a building was suitable for a PV system. Factors considered during this site assessment included roof slope, roof orientation, roof material, and shading.

Size. The size of the systems ranged from 0.9 to 2.4 kilowatts (peak DC) capacity.

Net Metering Requirements. All the PV systems utilize net metering.

Participant Building Characteristics

All buildings participating in this demonstration project are within the NorthWestern Energy electric service area. Each was required to be connected to the NorthWestern Energy (NWE) distribution system and to have a NWE electric meter.

Additionally, each building is occupied by the homeowners (or long-term renters) year around. The building owner had to provide the building’s electric bills for the previous 18 months or allow NCAT access to the bills (for a baseline determination), and to sign a net metering agreement with the NorthWestern Energy.

The buildings are all single-story structures. NCAT chose this type of building because of safety considerations for the installation crew and for ease of installation.

One of the building’s roofs had to be south-facing and have an area of at least 300 square feet. While PV arrays do not require guaranteed access to sunlight from sunrise to sunset, participating buildings were evaluated to ensure that they experienced minimal shading between 8:30 a.m. and 3:30 p.m. solar time, when nearly 90 percent of the sun’s energy reaches the site. With any solar energy system, shading should be avoided and solar access maximized, as even partial shading on a PV array will significantly reduce the system’s electrical output.

Although the PV system should ideally face true south, a deviation of 45 degrees or less from true south was permitted because it did not substantially reduce a roof-mounted system’s annual performance. Therefore, a building’s roof oriented 45 degrees or less from true south was considered for the PV system installation.

The preferred roof slope was 45 degrees (a 12/12 pitch), but roof slopes between 23 degrees (5/12 pitch) and 60 degrees (21/12 pitch) were considered acceptable. Although most roofs can support the added weight of a PV system, homeowners were asked to check the condition of the rafters and determine if the roof could safely support the added dead load of the PV array and mounting rack and the temporary live load imposed by the installation crew. The PV array and mounting rack add approximately 3 pounds per square foot of dead load to the roof.

The south-facing roof had to be near the main electrical service entrance. To minimize wiring runs, the breaker panel containing the building’s main disconnect switch and the household’s electrical end-use breakers had to be easily accessible and relatively close to the PV array. The breaker panel had to have space available for installing a 120/240V breaker; this is the PV system’s connection to the electrical grid.

Participant Recruitment

NCAT issued a news release (see attachment) on April 18, 2001, announcing the project and soliciting applicants. The release was sent electronically to all Montana daily and weekly newspapers. A hardcopy of the press release was faxed to the Billings Gazette, Bozeman Daily Chronicle, The Montana Standard (Butte), The Missoulian, Independent Record (Helena), The Daily Inter Lake (Kalispell), Livingston Enterprise, Miles City Star, and the Great Falls Tribune. The release also was sent electronically to all Montana solar dealers with email addresses, and a hardcopy was mailed to those dealers who did not have email capability.

Qualifying Applicants

Each applicant submitted a completed application to NCAT, which included site photographs and a bid from the contractor who would provide the hardware and complete the installation.

NCAT strived to attain a wide geographical distribution when selecting sites for the project. The locations and number of installations are:

  • Anaconda 1 system
  • Billings 1 system
  • Bozeman 2 systems
  • Butte 1 system
  • Lewistown 1 system
  • Missoula 2 systems
  • Red Lodge 1 system
  • Ryegate 1 system
  • Three Forks 1 system

For more information, see the Site Addresses and Photos attachments.

NCAT entered into individual agreements with each homeowner. This NCAT/homeowner agreement provided a description of the work to be performed and the warranties provided by the contractor. The homeowner signed this agreement before work began. The homeowners assumed ownership of the PV systems, after acceptance.

Installation Contractors Used in the Project

Tony Boniface
Independent Power Systems
1627 W. Main St
Bozeman, MT 59715
Phone: 406-587-5295
E-mail: [email protected]

Stan Nash  
Anaconda Electronics Co.  
111 Woodstack Trail  
Anaconda, MT 59711  
Phone: 406-560-2109  

William von Brethorst  
Planetary Systems  
Box 340   

Ennis, MT 59729  

Phone: 406-682-5644 
E-mail: [email protected]  

Lee Tavenner
Solar Plexus
130 West Front Street
Missoula, MT 59802

Phone: 406-721-1130

E-mail: [email protected]

Henry & Barbara Dykema
Sundance Solar Systems
P.O. Box 404

Luther, MT 59051
Phone: 406-425-1153
[email protected] 

Solar Electric System Specifications

Solar Modules. The contractors provided each home with photovoltaic modules to make up arrays with an output ranging from 0.9 to 2.4 kilowatts (peak DC). The modules were framed and composed of flat-plate monocrystalline silicon cells. The modules had a UL 1703 listing and were warranted by the manufacturer to provide no less than 90 percent of rated power for 10 years, and 80 percent for 20 years.

Mounting Structure. The contractors provided all the materials for mounting the PV array flush on the roof, anchored to the ground, or mounted on a pole. The mounting structure is capable, at a minimum, of withstanding winds of up to 90 mph, and is constructed of corrosion-resistant steel or aluminum.

The Inverter.
Contractors supplied and installed an inverter for each system to allow grid connection (120VAC, 60Hz). The inverter has a UL- or ETL-1741 listing, contains maximum power point tracking, islanding protection, over/under voltage disconnect, over/under frequency disconnect, automatic fault condition reset for loss of grid and voltage/frequency variations, GFI protection, AC and DC disconnect switches, and a five-year warranty.

Disconnect Switch. Contractors provided a lockable AC disconnect switch located in an outdoor-rated enclosure mounted near the main electric meter for utility personnel use. The disconnect switch was mounted within 10 feet of the electric meter and labeled "Solar Electric Generator Disconnect Switch." In cases where the meter was far away from the PV system, the contractor labeled the meter base with "This net meter is connected to a solar electric generating system."

Miscellaneous Electrical Equipment. Contractors provided all the wire, conduit, and hardware required to connect the PV modules, source combiner box, inverter, outdoor AC disconnect switch, residential meter base and watt-hour meter, and AC connection to the breaker panel.


Depending on the inverter installed at the home, the homeowner may view data from their PV system on an inverter display. Data available on this display are AC volts, amps, frequency, DC volts, output power (watts), and daily watt-hour production. A cumulative watt-hour meter was installed on ten homes to keep track of the PV system’s AC electrical output; one home is able to download the accumulated kWh production from the inverter.

Lessons Learned/Experiences

This project was carried out during a year that experienced an energy crisis, which created a huge demand for large wattage photovoltaic modules in California. In addition, the year showed an increased demand in third world countries for photovoltaic systems. Thus, it was impossible to meet the initial October 15, 2001, installation deadline for the residential systems. The last two installations were completed and signed off by NCAT staff on December 22. In one case, the inverted requested by the homeowner was backordered and the installation is delayed until mid-February 2002. While the long lead times for acquiring the equipment was beyond NCAT’s control, it was frustrating nonetheless. Homeowners who subsequently withdrew their applications from the program caused another delay. A total of 22 homeowners initially applied to participate in the program. Of those 22 sites, 10 homes were equipped with photovoltaic systems in 2001, 11 homeowners withdrew from the program, and one system installation was delayed until mid-January 2002 because of a backordered inverter.

Reasons for withdrawing from the program varied. In two cases, one spouse wanted the system and the other didn’t. Two additional homeowners were laid-off from their jobs and couldn’t afford the systems. The remaining seven homeowners decided the PV system was not a cost-effective use of their money.

While withdrawals are perhaps to be expected, having such a high number of withdrawals did delay the project and ultimately meant that NCAT was only able to install 11 systems instead of the available 15.

Last year, NCAT collected the required co-payments from the homeowner and paid the PV dealer/installer when the PV system was installed. This year, NCAT paid the $4,500 rebate to the homeowner after the system was installed, the local electrical inspector signed off on the installation, and NCAT staff verified the system. This second approach is the preferred method of dealing with the homeowner, the money, and the dealers/installers of the PV systems, as it affords a much simpler process. Last year, one dealer/installer was used in the program; this year, five Montana dealers/installers benefited from the project by installing from one to four systems each.

Because the money for 15 systems funded under this year’s program was not fully allocated, the money for the four systems not installed ($18,000) was carried over to the 2002 program. The Residential Solar Electric Demonstration Program in 2002 was proposed to install 15 kW of residential photovoltaic capacity; with the carry-over funds, the 2002 program will fund up to 19 kW of installed capacity for grid-connected, net metered residential photovoltaic systems.

Follow Up

At the end of 2002, NCAT will provide a performance report of the electrical outputs for the PV systems installed in 2001.

Solar Program Lets Homeowners 
Generate Their Own Green Power

Homeowners connected to Montana Power Company’s electric distribution service may be eligible to participate in an exciting solar electric demonstration projects that will save money and protect the environment by generating "clean" energy from a free resource—the sun.

The National Center for Appropriate Technology, through Montana Power Company’s universal system benefits fund, will provide $4,500 incentive payments to selected homeowners who install a solar electric system. The systems must be at least 1 kilowatt in capacity. The owner will choose a solar dealer who will supply and install the system. NCAT will approve the system design and inspect the installation.

The grid-connected solar electric (often called photovoltaic, or PV, systems) will be installed on as many as 15 homes this year. Twenty-four homeowners installed solar electric systems through a similar incentive program in 2000.

The solar electric systems will be utility-intertied, which means the electricity they produce can be fed into the utility grid, in effect running the meter backward.

Solar electric systems are easy on the environment. They help reduce the use of fossil fuels and resulting greenhouse gas emissions.

A 1-kW solar electric system, for example, will eliminate the emission of more than 1,750 pounds of carbon dioxide and nearly a half-pound of nitrogen oxides annually. And solar electric systems save money by generating their own "clean" electricity from a renewable energy resource.

A solar electric system produces direct current electricity, which is converted by an inverter into alternating current (AC) electricity at the utility's voltage and frequency. The AC electricity is fed into the building’s main electric breaker panel.

AC electricity produced by the solar electric system is consumed in the building and any excess electricity produced by the system goes back into the utility grid. MPC will install electric meters that turn backward whenever excess power generated by the solar electric system is fed into the utility grid. The homeowner must sign a net metering agreement with MPC for this project.

Qualifying homeowner applicants must meet basic requirements such as having an acceptable solar installation site. A qualified dealer must install the system. NCAT will inspect each system before the homeowner will be reimbursed. Participants will be randomly selected from the pool of qualifying applications.

Funds for the project come from the universal system benefits charge, or USBC paid by all Montana Power Co. customers.

For information, contact John Walden at (406) 494-8641 or Ray Schott at (406) 494-8668.

NCAT, a national non-profit organization headquartered in Butte, promotes sustainable technologies and community-based approaches that protect natural resources and assist people in becoming more self-reliant.

2001 Solar Demo Homes
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