This Solar House

Solar, Part 1 (Dec 2003)
We moved into our 2,300-square-foot house around Thanksgiving 2003. Within a month, in order to make use of state rebates that would decrease after the first of the year, we purchased a 6-kilowatt photovoltaic (PV) system. Installation occurred in two phases. First, in December, we installed the 4-kW array of 35 sapphire-blue PV panels that you can see on the south-facing side of our main roof; eight months later we added the 2-kW set over the garage (see "Solar, Part 2" below). This 6-kW PV system supplies all our energy needs, from our home's heating and air conditioning to the "fuel" for our electric car. (To learn how PV panels work, see Inside a Solar Cell.) Cost: $36,000 (6-kW system; after rebates and tax incentives totaling $17,500, our out-of-pocket expenditures came to $18,500)

Insulation (Jan–Feb 2004)
As part of our goal to make our home net-zero-energy—that is, generating more energy than is consumed—we set about improving our home's insulation. In January, we contracted a company to inject cellulose (recycled paper) insulation into the walls, bringing them up to an R15 level. (The R-value indicates the resistance of a material to the passage of heat and cold.) The following month, we replaced our leaky, single-glaze aluminum windows with dual-pane thermal windows. These are so-called "low-emissivity" windows, which keep winter heat in and summer heat out. We left our front picture window (behind car in main image and at left) intentionally non-low-emissivity, so the winter sun could warm our living room—a passive solar technique. Cost: $1,300 (insulation), $10,000 (dual-pane windows)

Roof (Mar–Jul 2004)
To further increase thermal resistance, we decided to replace the roof and upgrade our attic insulation. In March, we removed the 4-kW solar array as well as the existing, substandard roof tiles. The following month, we brought the attic insulation up to an R30 level. Then, in June, we installed aluminized solar sheathing on the roof. This is a thermal reflective plywood that keeps external heat out and reflects interior heat back in. We also installed roof jacks (to hold up the solar array) and then a new composite shingle roof. Finally, in July, we put in a whole-house cooling fan and whole-house heat-recirculating system (as well as two skylights, one seen in the center of the roof). The fan cools the attic and ceilings when outside temperatures are high, while the heat fan shuttles warm air from the attic to the ground floor when outside temperatures are low. Cost: $300 (attic insulation), $23 per 4' x 8' board (solar sheathing), $4,000 (new roof), $600 (whole-house fan), $570 (whole-house heater), $1,450 (two skylights)

Solar, Part 2 (Aug 2004)
This month we reinstalled the 4-kW solar array over our main roof and put in place the 2-kW, triangle-shaped array of 14 panels over our garage. Our now 6-kW solar system includes a 4-kW inverter to convert the DC electricity coming from the solar panels into AC to power our appliances. Most homes wouldn't require a 6-kW system; we added the extra 2-kW solely to power up the 24 nickel metal hydride batteries in our Toyota RAV4 all-electric vehicle (seen in main image). In fact, because we now generate more solar energy than we can use, we welcome friends who own electric vehicles over to charge their car batteries for free. Cost: included in costs noted in "Solar, Part 1"

Battery Backup (Sep 2004)
To be prepared in case of blackouts, we installed an 8-kW battery reserve system. This includes an inverter and charge controller that regulate energy flow to and from the batteries. If the utility grid goes down and we have a string of very overcast days, our batteries will give us about three days worth of conservative electric use. If the sun is shining, we have unlimited energy, of course. Cost: included in costs noted in "Solar, Part 1"

Solar, Part 3 (Oct 2004)
This month we replaced our natural gas-fired water heater with an active, closed-loop solar hot water system (see the two gray solar panels visible on the left side of the roof) and a new 220-volt electric hot-water heater. Cost: $2,500

New Heating/Cooling (Jan 2005)
The final step in making our house comfortable involved replacing the old, five-ton heating, ventilation, and air conditioning (HVAC) system with a split-ductless heat pump/HVAC system. This is a three-zone system, with small units in the den, dining room, and upstairs master bedroom. The system has an outside central operating unit and a compressor-heat exchanger that is about half the size of a typical air conditioner. Cost: $4,200

Costs & Benefits
After $18,500 in rebates and tax incentives, the total cost for all our energy-efficient improvements and our solar system, including labor, came to $43,000. We calculated that, if we had not made the retrofit, our energy bills for 2004, including fuel and oil for a gas-powered car, would have come to $6,000. With the upgrades, we have no energy costs (except for $5 a month for the one therm of natural gas we use, mostly for cooking). Thus, our entire energy makeover will pay for itself in just over seven years ($43,000/$6,000 = 7.2). And because our loan for these improvements is based on home equity, the interest payments are tax-deductible.

Since we remain connected to the utility grid, Southern California Edison's time-of-use billing program measures our overall electricity consumption and production. Rates vary depending on season and peak versus off-peak hours. With normal sunshine, we can actually see our meter "feeding the grid." Our electricity production earns us "use-it-or-lose-it" credit from the utility. In summer peak hours (10 a.m. to 6 p.m.), we can earn over 40 cents per kilowatt-hour; even during off-peak summer hours and in winter, we can earn credit. Each year, our credit amounts to between $200 and $300.

It's true that we live in warm, sunny California, which has some of the best rebates and tax incentives for going solar in the nation. But wherever you live, you can benefit from energy-efficiency and renewable-energy upgrades to your existing home and become part of the solution to global warming. See Resources for more general information. For more specifics on the Williamsons' retrofit, see this article published in Solar Today Magazine, from which our feature was drawn.

*Note: "Zero-energy" here refers to energy purchased, not energy used.