For the past eight years, I have been teaching solar electricity workshops for Solar Energy International (SEI). It’s always been important to me to practice what I teach, so I can help students from firsthand experience. The funny thing is that my life keeps changing, and every time it does, I am again faced with a new home upgrade to meet my sustainability goals.
When my husband Mike and I were first married, we rented a little two-bedroom, one-bath apartment. Since we didn’t own the place, we weren’t in a position to invest in a solar-electric (photovoltaic; PV) system, but we did what we could to make the apartment low impact in terms of our energy use. We installed compact fluorescent (CF) lightbulbs, purchased blocks of wind power from the local utility, and even succeeded in talking our landlords into upgrading the apartment’s ancient refrigerator with a new, energy efficient model.
When our daughter Ruby came along, we decided it was time to purchase a home that would accommodate our growing family. We bought an existing house, instead of building from the ground up, for a couple of reasons. First, it would immediately provide more space for the three of us. But more importantly, we liked the idea of buying, rather than building, for environmental reasons—think of it as house “recycling.”
Upgrading older homes for energy efficiency almost always results in a net decrease in resource consumption, because fewer construction materials need to be harvested, manufactured, and transported. With this in mind, we set out to reduce our energy use in this 3,000-square-foot home, and install a solar-electric system to meet all of our electricity needs.
When we moved into our new home, the first thing we did was replace all incandescent lightbulbs with compact fluorescents, which only consume about a quarter of the electricity of incandescent bulbs, while providing the same amount of light.
Next, we used a watt-hour meter to determine which of our appliances use energy even when they are turned “off.” We placed all of them—computer equipment, TV, VCR, and DVD player—on plug strips so we could conveniently and completely shut them down when not in use. Finally, we replaced the old pink 1970s-era refrigerator, dishwasher, and washer/dryer set with new Energy Star models (see Appliance Upgrades table for details).
The average U.S. home consumes about 940 kilowatt-hours (KWH) of electricity each month. The simple efficiency upgrades we made allowed us to bring our average monthly electricity consumption down to 210 KWH per month—or 7 KWH per day—less than a quarter of what a typical household consumes.
These basic energy efficiency strategies reduced our electric bill and also helped us meet our environmental goals. For every KWH we do not use, about 2.2 pounds of carbon dioxide (CO2), a greenhouse gas, is kept out of the atmosphere, along with other pollutants emitted from the coal-based power plants that provide most of the utility electricity here in Colorado.
While our motivation for reducing electricity demand was primarily environmental (at about 8 cents per KWH, electricity rates in our town are relatively cheap), our goal of reducing our natural gas usage was primarily economic. During the first winter in our new home, we faced gas bills in excess of $360 per month! To reduce our natural gas consumption, we added another 12 inches of blown-in insulation on top of the fiberglass batts in the attic, and undertook the expensive project of replacing all the old, leaky aluminum-framed windows with new, top-quality double-pane, vinyl-framed windows. The new windows and increased insulation alone reduced our natural gas consumption by more than 25 percent.
Finishing our energy efficiency upgrades just happened to coincide with some favorable legislation that got our PV system off the “wish list” and out into the sun, generating clean, renewable energy. Last year, Colorado voters passed Amendment 37, which requires investor-owned utilities (IOUs) servicing Colorado to obtain 3 percent of their electricity from renewable energy resources by 2007 and 10 percent by 2015. As a result of this legislation, Xcel Energy is offering a solar-electric rebate program to customers in their territory.
Though we are not serviced by Xcel Energy, for a limited time, they also offered to buy renewable energy credits (RECs) from PV systems in Colorado that are outside of their service territory and purchase the RECs with a one-time payment of $2.50 per DC watt of installed PV. The Xcel Energy REC purchase offer, combined with the $2,000 federal tax credit now available for solar-electric and solar hot water systems, gave us the financial incentives we needed to design, purchase, and install our PV system immediately (see PV System Costs table).
Our local utility, Delta Montrose Electric Association (DMEA), offers net metering for systems up to 25 KW. Ironically, while DMEA is one of the progressive utility cooperatives in Colorado, their $20 monthly minimum utility bill policy can undermine the financial benefits of residential-scale grid-tied PV systems. The result is that even if you offset all of your electricity consumption with a solar-electric system, you will still be charged $240 each year for electricity! While this policy significantly reduces (or may even negate) the financial payback of a grid-tied PV system in their service territory, and is in direct conflict with energy efficiency and green power strategies otherwise promoted by DMEA, we refused to be deterred from accomplishing our green power goals.
Our initial goal was to design a grid-tied PV system that would offset 100 percent of our annual electricity use. The next consideration was whether to include batteries to provide a backup energy source for some of our household appliances when the utility grid goes down. We rarely experience utility outages at our location, and when we do, they are typically short in duration and don’t inconvenience us much, so we opted for a batteryless system. In fact, we look at utility outages as a nice little break from all the technology that surrounds us day in and day out.
We used our average annual electrical consumption of 2,520 KWH to size our PV array (see System Sizing Calculations sidebar) and, after making a few calculations, determined that a 1.7 KW array would meet our electrical needs. Our home’s roof faces east and west, and has trees blocking the sun on both sides. Thankfully, we didn’t have to do much tree trimming to allow the south wall of our house full solar access from 9 AM to 3 PM—the optimal solar window. The two-story construction of the house allowed us to design an awning structure to support a PV array that would both generate electricity and, during the summertime, shade our first-floor windows, while admitting full sun through the windows during the winter months.
We decided to use Mitsubishi modules (sourced from Bob-O Schultze of Electron Connection) and a Fronius inverter. We also ordered a prefabricated Direct Power and Water (DP&W) mount that we could simply attach to the house. Jeff Randall from DP&W helped us adapt their standard mounting structure for our particular situation. The roof–ground mount is normally installed so that the adjustable legs sit underneath the top of the array. For wall-mounting, we flipped the mount so that the legs would be adjustable from the bottom of the array.
Our PV project coincided with one of SEI’s PV Design and Installation workshops, and we were fortunate to have several of the students volunteer to help with the installation. Their skills and attention to detail were top notch. We spent two and a half days mounting and wiring all the system components—PV array, AC and DC disconnects, inverter, and an AC PV system production meter (required by our local utility)—along with mounting the junction box and wiring gutter, running and securing the conduit, pulling the wire, and, finally, completing all wiring connections.
On the last day of the installation, after double-checking our wiring and connections, it was finally time to bring the system online. Once the inverter was energized and producing electricity, we all rushed over to see the electrical meter merrily spinning in reverse! And as all of us were cheering, I was reminded that this was the first grid-tied PV installation these students had been involved with, and what a thrill it is to see solar energy hit the grid for the first time.
The system has worked flawlessly since its installation. When the sun is shining, the PV array produces more electricity than we typically use around the house. In this case, our electrical meter spins backwards and the utility gives us a “credit” for the surplus kilowatt-hours generated. When the PV array produces less electricity than we consume, we simply pull whatever amount of additional electricity is needed from the grid, dipping into our surplus credits.
The Fronius inverter and its wireless display have proven to be very user-friendly, and overall system production has been impressive. On bright, sunny days during the fall, our 1,700-watt array produced about 10 AC KWH each day. Around the winter solstice, the system produced about 8 AC KWH on sunny days. This past year we experienced an unusually cloudy late fall and early winter, so our total KWH production has been lower than expected. But considering that our PV modules will generate electricity for 30 years or more, there’s a lot of sunshine—and solar electricity—coming our way!
It has been a fun and exciting project to blend our growing family needs with our “green power” goals. If your primary goal is environmental, it’s best to pursue energy efficiency strategies first. Once a home’s energy efficiency has been addressed, installing a PV system to meet the remaining electrical demand makes good sense, both financially and environmentally.
By investing in a PV system when we did, we were able to take advantage of solar incentive programs that reduced the up-front cost, while hedging ourselves against future electricity rate increases. But the primary factor that motivated us to invest in energy efficiency and PV technology wasn’t money or cutting-edge PV gear; we did it to create a cleaner environment for our daughter Ruby and the generations that follow.
Justine Sanchez, Solar Energy International, 39845 Mathews Ln., Paonia, CO 81428 • 970-527-7657 • Fax: 970-527-7659 • www.solarenergy.org
Electron Connection • 530-475-3401 • www.electronconnection.com • Equipment supplier
Direct Power and Water Corp. • 800-260-3792 • www.directpower.com • PV rack
Fronius USA LLC • 805-683-2200 • www.fronius-usa.com • Inverter & display
Mitsubishi Electric Corp. • 714-229-3814 • www.mitsubishielectric.com/products/solar.html • PVs