That’s an important distinction to remember in the grand scheme of an energy and environmental message to home buyers: Photovoltaic panels produce energy; the only energy they save, per se, is the electricity they offset from the power grid.
Conservation, by contrast, comes from smart building products and practices. A better-built home may allow a smaller—and thus less expensive—PV array to offset most of what the grid provides, but even then, the system carves only a small slice of the green pie.
For instance, Warmington Homes gained only six extra points within a local green building rating system for the standard, 2-kWh-per-unit PV system at Vantage, a 76-unit townhouse condominium project in Palo Alto, Calif.
The real return for Warmington has been an enviable sales pace at Vantage that has even allowed two price increases amid the deep discounts and other sales incentives that competing projects are offering. “It’s helped us achieve our sales goals and reliable absorption, no question,” says sales manager Debi Garlick.
Kramer has seen similar results at Encore, with one sale a week. And he reports that offering homeowners the ability to monitor their energy use and PV-system offset of the grid power inspires them to conserve energy even more. Some Encore buyers have received monthly electric bills in the single digits, less than 10% of what they would likely pay for a code-minimum house without PV.
Encore’s electrical-use cost offsets average in the 70% range, aligned with what PV gurus promote as a reasonable and attainable peak-performance (ideal conditions) goal with a 2- to 4-kWh system. Not only does that size of a system significantly lower a homeowner’s utility cost burden, but a builder’s investment as well.
The industry-average cost per installed kilowatt of PV is about $10,000, perhaps less for more capacity and multiple-unit systems. Various rebates, tax credits, net metering, and other financial incentives to both builders and home buyers might cut that expense in half or more. At that scale and with those incentives, a PV system becomes more financially attractive, it’s cost more easily recouped in an accelerated home sales pace, if not a higher sales price under current market conditions.
Buyers also may appreciate knowing that solar-powered homes are hot on the resale market, as well. The National Appraisal Institute estimates that an annual energy-cost savings of $800 achieved with a PV system equates to perhaps a $16,000 or 20% bump in property value, a distinct market advantage.
But that window is closing. PV shipments to the residential sector have risen substantially every year since 2003, specifically 28% in 2006, the latest figures available from the Energy Information Administration. The combined factors of ever-rising energy costs; federal, state, and local incentives and mandates for green building (and PV, specifically); and built-in system designs that render the panels nearly unnoticeable signal continued growth.
“The way these homes are built is the way of the future,” says Kramer of the comprehensive approach Meritage took with Encore, including PV. “You might as well get ahead of the curve.”
Rich Binsacca is a freelance writer in Boise, Idaho.
How It Works
Parts of a Solar Power System
Solar Collectors: (On the roof.) Collectors deliver DC power to the system inverter.
Inverter: (Small blue box in cutout.) DC power from the solar collectors feeds into the inverter that converts it to utility-grade AC power.
Load Center: (Large white rectangle next to Inverter in cutout.) The load center distributes AC electricity to the house and grid as required.
Utility Meter: (Outside wall.) A utility meter tracks electrical use as well as solar energy fed into grid.
Residential photovoltaic (PV) systems consist of silicon-based, semiconductor-material solar cells that combine to create modules or panels, which are then ganged on the roof or on the ground as arrays to collect the sun’s energy. The layered design of the cells and panels, the precise components of which vary among manufacturers, collects as much solar energy as possible, even on cloudy days and in occasional shade. That being said, the ideal placement and orientation of any solar array is on a large, south-facing surface, preferably a roof, that is unencumbered by shade trees, roof penetrations, or other objects. Whether the weather is hot or cold is immaterial, though the seasonal location of the sun’s path does impact the amount of light to capture. Ideally, the array is angled to the location’s latitude to capture solar energy at its most intense level. Fewer daylight hours in winter result in proportionately less power generation.
While traditional rack-mounted systems still prevail, the latest evolution of solar cell technology features built-in panels that visually integrate into the roof finish and slope. Dimensional panels and tiles are designed to look like and replace roof shingles, standing-seam metal, or concrete roofing products to improve their aesthetic acceptance.
PV panels and their component parts have no moving parts and emit no pollutants in their operation. Standard electrical wires transmit the energy they collect as a direct current (DC) to a centralized inverter. The latest PV systems average about a 12% conversion ratio between the sunlight that hits the panels and the amount of energy they can collect, though conversion rates are rising—and panel sizes shrinking—as solar cell technology evolves. The inverter converts the DC power collected to alternating current (AC) power—usable electricity for most household needs—a process that itself sacrifices another 15% of the energy collected. The AC power is then sent to the load center, from which it is either distributed through the house or sent back to the utility as energy credits to be used later, a process called net metering.
In the past, a common—if idealistic—goal was to achieve a “net zero” electricity balance, in which a residential PV array and battery storage system generates all of a home’s electricity needs, thus rendering utility-grid power supplemental or unnecessary. Today, primarily to keep installation costs in check and maintain the reliability of an always-on utility power source, most residential PV systems are scaled to offset the peak-use times and rates of grid-provided power, usually in the mid-afternoon to early evening hours, and hopefully generate some energy credits to further reduce utility bills.