fluid flowing through it to transport the collected heat to somewhere useful, such as a hot water tank or household radiators. The solar panel is located in an area prone to ample light exposure throughout the day—usually on the roof, and a pump circulates the heat-transfer liquid throughout the system. Also available are “solar hot air” systems that are simpler in design and basically heat air drawn through panel and then recirculate back into the room. The systems are typically used as a supplemental heat source. Solar thermal systems can be quite expensive to install, and they also require unobstructed expo- sure to the sun, meaning they’re installed on roofs and walls where many homeowners don’t like the obtrusive appearance of the pan- els. Although solar systems are expensive, they do qualify for 30- percent Federal tax credit in the U.S. SPACE HEATING Don’t overlook space heating as a simple but effective tactic to reduce energy bills. The average annual cost to heat an average 1,500 square-foot house at 70 degrees is roughly $1,800. With such high costs, it makes good sense to heat only the rooms in which you spend the most time, rather than heat the whole house. Although it does rely on tradi- tional electrical power, targeted heating with space heaters can be a clean, easy and unobtrusive method of reducing overall energy usage.