Rheem’s SolPak solar hot-water heating package contains two solar collectors, a heat-exchanger tank, an adjustable pump, an expansion tank, a controller, and four gallons of glycol solution. Collection panels come in 3-by-8-foot and 4-by-8-foot sizes, and tanks in 80 gallons and 119 gallons. Pricing starts at about $4,000. Rheem, 800/621-5622, rheem.com.