DOING THE MATH
Florida provides rebates for photovoltaic systems of 2 kilowatts or bigger. A system that size will generate 8 to 10 kilowatt hours a day.The cost averages $12 a watt installed with enough hardware to hold the panels on the roof in 150-mile-per-hour winds, said Dan Morris with Vergona Bowersox in Boca Raton, an electrical contracting firm with a PV division. That would total $24,000 for a 2-kilowatt system.Florida pays $4 a watt to offset the cost, or $8,000 on the 2-kilowatt system. The federal tax credit for homeowners is a flat $2,000.Therefore, with a $10,000 total rebate, the $24,000 system will cost a homeowner in Florida $14,000.
And while the south side purposely presents a demure if somewhat pinched facade, the north demeanor is typically Keys-ean with stately porches, wide overhangs and French doors opening to the buttonwoods, beach and Florida Bay.
John Hammerstrom, an airline pilot, and Diane Marshall, a creative writing teacher at Florida International University, built the home in 2002. Former Californians with an eco-consciousness, the couple couldn't find the features they wanted in existing Keys houses, so they bought a lot, did their research and created their green dream.
Alternative energy is coming back into fashion as environmental concerns grow and temperatures climb along with the price of oil, hovering near $80 a barrel. The sun's potential power is greatest in the southwestern desert states, but Florida gets some 75 percent of the maximum daily sunshine, enough to power many appliances.
''We're getting all kinds of inquiries,'' said Paul Landino, owner of eMarine in Fort Lauderdale. ``We have been selling self-contained power systems to the islands and doing a lot of land-based stuff here, too.''
State and federal rebates are making systems more affordable. Interest in photovoltaic systems as emergency power during hurricanes is increasing as well.
During Hurricane Wilma, Hammerstrom and Marshall stayed put. With hurricane shutters, solar power, a cistern and steel-reinforced concrete pillars securing their porches, they felt confident enough to ride out the storm.
''During the few times that the power goes out, we get very conservative,'' Hammerstrom said of their energy use.
Learning how to put together the systems that make their home green turned the couple into local experts. Marshall, who wanted to share what they learned, helped create the Keys GLEE Expo (Green Living and Energy Education), an annual workshop that showcases green materials, building techniques, landscaping and even solar cars. (The next one will be May 9 through 11 in Marathon.)
While it is possible to disconnect from an electric power grid with photovoltaics (PV), the couple opted to stay attached and have the utility-generated power run the air-conditioning system, the microwave and dishwasher. Any time their PV system produces an excess of energy, they can send it back to the Florida Keys Electric Cooperative and receive credit.
LIGHTS AND FANS
Their PV system powers compact fluorescent lights and fans in the three bedrooms and three baths, the living room, plus the Energy Star refrigerator, computers, pumps on the water circulation system and washing machine -- about 30 percent of the electricity used in the home throughout the year.
The 2,450-square-foot home, with an additional 1,400 square feet of porches and decks, cost about $300 a square foot (including the ample amounts of interior woodwork), or 15 to 20 percent more than a conventional home, said Hammerstrom.
Their highest electric bill has been $138; in the spring, when the doors and windows can be opened, that amount drops to $20.
The PV system cost $25,000, but rebates worth $11,000 took a significant bite out of that. In addition to the 24 panels on the roof, the system includes eight 6-volt golf-cart batteries to store the energy and an inverter. The inverter, which Hammerstrom calls the brains of the system, converts the DC power to AC and sends it to the appliances and lights. It also monitors the batteries and keeps them full.
The interconnection agreement with the Electric Coop is the first ever written in the Keys, said Hammerstrom.
Energy efficiency makes the PV system work, Hammerstrom said. He saves $10 on energy for every $1 he spent making the house energy efficient. The couple opted for the following:
• A white metal roof to reflect the sun's heat away from the house. They decided against a radiant barrier below this because it would only hold in heat rising from the house.
• Small windows and extra insulation on the south-facing wall.
• A 40-gallon solar water heater on the roof.
• Sealed, insulated duct work that is mostly contained within air-conditioned space.
• A gas range and cooktop.
• Miele low-energy and low-water dishwasher.
• Kenmore front-loading washer and gas dryer.
• A cupola with operable windows to draw warm air up and out of the house.
• Hampton Bay ceiling fans designed by Danny Parker of the Florida Solar Energy Center (sold at Home Depot).
• Low-flow shower heads.
• Bamboo floors and stairs. Bamboo is fast-growing and can be reharvested every five years.
• Formaldehyde-free insulation in the ceiling crawl space, exterior and interior walls.
• French doors with wood on the interior and vinyl-clad on the exterior with operable transom windows attached.
• Custom clerestory windows in interior walls for cross ventilation.
Following in a long Florida Keys tradition, Hammerstrom and Marshall also have a cistern. But this contemporary interpretation goes beyond the open, rain-fed concrete tanks of years ago. This one is rain-fed, but with slick differences.
Gutters direct rainwater from the roof to two large PVC pipes. The first rain off the roof, which holds the most dirt and debris, is allowed to drain away. Gradually, a Ping-Pong sized ball lowers into the drain and clean water then is backed into the cistern. After a day, the drain stopper gradually rises again.
CISTERN SPLIT
The cistern is divided in half, with the first compartment decanting water into the second. In addition, Hammerstrom has installed a series of filters on the cistern to clean the water before it is brought into the house: a 1-micron filter for fine sediment, a carbon filter for chemical contaminants and a UV filter chamber for water sterilization.
''The UV sterilizes in case there is any bacteria from bird poop, lizard poop or any other type of contamination that could get into the cistern,'' Marshall said. And like their solar/electricity set-up, Hammerstrom and Marshall have fashioned a split water system: They can use city water or cistern water, depending on their needs.
''We prefer to drink cistern water because it doesn't have chlorine and other chemicals required in the city water,'' Marshall said.
They sent up three valves to control where the water comes from and goes. Valve one delivers water to the kitchen island sink. Valve two delivers water to the sinks, laundry and showers throughout the house. Valve three delivers water to toilets and outdoor hose bibs.
The water in the kitchen sink is always from the cistern. If the cistern has more than 600 gallons of water in it, the laundry, sinks and showers draw from it, too. Early in the rainy season, the outside hoses and the toilet water comes from the cistern; as the season dries, the hoses and toilets are put on city water.
HOT AND COLD
To keep from wasting gallons of cold water while the hot water from the rooftop solar water heater circulates through the pipes, Hammerstrom has installed an ''on demand recirculation system'' that uses a small pump to move hot water more quickly. A button just beneath the light switch in each bathroom is pushed, ''you can change your clothes and in 90 seconds, there will be hot water for your shower,'' he said.
