Overview: How a solar hot water system works
If you've ever left a garden hose lying across your lawn on a sunny day and felt the nice hot water coming out the end, you know that sunlight is an effective water heater. Solar hot water systems of yesteryear were often leaky, failure-prone and ineffective, but the industry has matured. Today, you can choose between super-efficient, professionally installed collectors and this less expensive DIY-friendly system. And if federal tax credits are available or additional state and local incentives, you may be able to recoup your investment in a few years, and enjoy cheaper hot water for years beyond that.
Using a solar water system doesn't mean surrendering the convenience of your regular hot water system. Solar hot water systems are designed to tie in to conventional electric and gas water heaters. The tank stores the solar-heated water and serves as a backup heat source. Even if the water from the collector isn't shower-hot, you'll still save money since your tank will have had a head start heating the water. With all solar water systems, it's vital that the panels be installed where they will receive the most direct sunlight. Ideally, you'll want to use a south-facing section of roof. An east- or a west-facing roof will also work, but you'll need additional panels to collect the same amount of heat.
Closed-Loop Solar Heating System
Here's how it works. When the controller senses that the sun is shining and your tank needs a warm-up, it signals the pump to send water through the black collector panels. The heated water then flows into the storage tank before it's channeled into the heat exchanger. There, it transfers its solar heat to the cooler water coming from your hot water tank. In this closed-loop system, the water in the panel never mixes with the water in the tank, so there's no chance of contamination. When the sun is down or the temperature drops, the controller protects the panel from freezing damage by automatically draining the rooftop panels into the storage tank.
A dependable, affordable DIY system
Until now, most solar hot water systems have required professional installation with a price tag of $4,000 to $8,000.
But here is an affordable (about $2,000) alternative that you can install in a weekend if you have rudimentary plumbing skills. FAFCO's Hot2O system (search fafco online) uses unglazed polymer collectors (photo above) instead of glazed flat-plates. Although the system is less efficient than professionally installed systems, the lightweight panels don't require roof reinforcement and are easy to install.
The kit includes everything you need to connect the solar panels to your existing electric water heater on a single-story house (you may need extra tubing for two-story homes). If you have a gas water heater, you'll need to add a second tank to store the solar-heated water and purchase a hook-up kit from FAFCO. Or you can use your old water heater as the storage tank and replace it with a new, more efficient water heater. The solar-heated water from the second tank is connected to your water heater, saving you energy and money.
Estimate the Payback
To estimate the cost, system size and payback of a solar hot water system for your home, go to the American Solar Energy Society's Web site, ases.org, and click on “Go Solar.” This site can also help you locate a professional installer for higher-efficiency systems to help determine the actual costs.