Harnessing the Sun's Power Solar Design, Heating Systems and Photovoltaics

Designing a New Home	Solar Water Heating	Photovoltaics
Solar Permit Fees	Solar Providers Guide	Solar Organizations

Heating Water with Solar Energy

What is a solar water heater?
A solar water heater uses the sun's warmth rather than electricity or gas to heat water for your home, pool or spa. A basic system consists of one or more black flat-plate collectors mounted on a roof. The collector absorbs the sun's heat and transfers it to water that circulates through tubing in the collector.

What are the benefits of a solar water heater?
It produces no air pollution or greenhouse gas emissions. It will lower your energy bills, especially if your current water heater runs on electricity and you use a lot of hot water. And it's easy to operate and requires little maintenance. How do I get hot water if the sun is not shining? A solar water heater is usually set up to serve as a pre-heater for a conventional water heater—ensuring you always have plenty of hot water.

Is a solar hot water system right for me?
It requires an unshaded location—ideally one that's south-facing to maximize exposure to the sun. Rooftop installations are the most common, but the collectors can also be mounted on the ground or a south-facing wall. They're great for heating pools and spas, but don't make as much sense if your household uses little hot water during the day. Solar water heaters can also be used to supply hot water to radiant heating systems that warm rooms by circulating hot water through pipes in the floor slab.

How much does a solar hot water system cost?
Costs depend on system size and other details. For a solar water heater for a pool, costs vary widely so get several quotes. A system for household use or space heating typically costs from $4,000-$8,000 installed. Rebates are not currently offered by the State.

Whole Building Design Guide: Solar Water Heating, comprehensive information on solar water heaters.

Generating Electricity with Photovoltaic Systems

What is solar power and what are its benefits?
Photovoltaic (PV) systems convert sunlight directly into electricity. Today's PV systems integrate easily with your home's existing electrical system. They produce clean energy—no air pollution, no greenhouse gas emissions. And they can greatly reduce—or even eliminate—your electricity bills.

How is a PV system installed?
PV systems can be mounted on a roof or trellis or even on the ground. They require a south-facing location with good sun exposure and no shading from trees or buildings. A device called an inverter converts the DC electricity produced by PV cells into the AC electricity required by our homes. The inverter is installed in a garage or utility room, or in an outside cabinet.

What is the difference between off-grid and grid-connected systems?
Off-grid PV systems aren't connected to the local utility's electricity network. They're more common in remote locations where it's expensive to hook up to the utility grid. Grid-connected systems are more common in cities and suburbs. Grid-connected systems feed excess electricity you produce into the grid and draw electricity from the utility when the sun isn't shining or when you need more energy than you're creating.

What is net metering?
It's special electricity metering and billing arrangement offered to California homeowners with grid-connected PV systems. When the sun shines, your home first uses the electricity from your PV system. If you need more, it's drawn from the utility grid. Any excess electricity you generate goes back to the grid, spinning your meter backwards! You're billed annually only for the net amount of electricity you used over the previous 12 months (total electricity used minus total electricity your system generated). If you install a PV system in an older home, you may need to replace the existing electricity meter with a new bi-directional meter.

What size PV system do I need?
System size depends on many factors, including available roof space, how much electricity your household uses and how much you want to generate. An average California household uses about 6,500 kilowatt-hours (kWh)of electricity annually. Taking advantage of Time-of-Use Net Metering, a 2.5 kilowatt (kW)PV system might be all that's needed to reduce this average electric bill to about $7 per month. PV retailers can help determine the best size to meet your needs based on your shading, roof orientation, usage patterns and location.

Do I need battery backup?
Off-grid PV installations usually include batteries that store electricity for use at night or other times when the sun is not shining. Batteries add a lot to the cost of a PV system. If you have a grid-connected system, you don't need battery backup unless it's critical that your power not be interrupted during local electricity outages.

What's the difference between crystalline silicon and thin-film PV?
These are the two basic types of PV technology. Crystalline silicon products usually take the form of 2X4-foot panels (size can vary). Thin-film PV is a newer technology—the PV cells are made into thin, flexible sheets or shingles. Unlike crystalline silicon panels, which are mounted on top of the roof, thin-film PV products can actually take the place of conventional roofing materials. Thin-film PV produces electricity less efficiently than crystalline silicon, but performs better in areas with less light, fog or partial shading.

Are rebates or tax credits available?
The State of California has been offering attractive rebates and tax credits to purchasers of PV systems. These incentives may not last, so check their availability before purchasing.

How much does a PV system cost?
Cost depends on size, type of system and other factors. Average cost (after rebates and tax credits) is $6,000-$8,000 per kilowatt. A 2-kilowatt (kW) system may cost from $13,500-$16,000 installed, after rebates and credits. Battery backup can add $3,000 to $6,000 or more.

The following organizations have detailed information on photovoltaic systems, rebates, and policy:

California Solar Center The California Solar Center website provides timely and accurate information to help develop the market for solar energy technology and design practices in California and to assist consumers, businesses, and policy makers move toward a clean energy future without compromising the environment or the economy.

Emerging Renewables Rebate Program The California Energy Commission is offering cash rebates on eligible renewable energy electric-generating systems through its Emerging Renewables Program.

Northern California Solar Energy Association NorCal Solar is a chapter of the American Solar Energy Society. NorCal Solar provides a variety of forums for exchange of information on solar energy applications and research through its website, the annual solar home tour, and the quarterly publication of The Northern California Sun.

American Solar Energy Society The County of San Mateo RecycleWorks Solar Tour is part of the seventh annual National Tour of Solar Homes and Buildings coordinated by The American Solar Energy Society (ASES). ASES is a national organization dedicated to advancing the use of solar energy for the benefit of U.S. citizens and the global environment. ASES promotes the widespread near-term and long-term use of solar energy.

PV Watts PV Watts calculates electrical energy produced by a grid-connected photovoltaic (PV) system. Currently, PV Watts can be used for locations within the United States and its territories. Researchers at the National Renewable Energy Laboratory developed PV Watts to permit non-experts to quickly obtain performance estimates for grid-connected PV systems. This is a useful calculator to determine how much energy your system will generate and how much you will save. To make the information the most useful, you should know what size system you might want (start with 2KW if you don't know), the slope of your roof, does it face south or somewhat SW or SE, and the cost per kwh that you pay.

Renewable Energy Policy Project REPP's goal is to accelerate the use of renewable energy by providing credible information, insightful policy analysis, and innovative strategies amid changing energy markets and mounting environmental needs by researching, publishing, and disseminating information, creating policy tools, and hosting highly active, on-line, renewable energy discussion groups.

Interstate Renewable Energy Council The Council is a non-profit organization dedicated to moving renewable energy resources into the marketplace.

Solar Tour 2004