The next step, for this example, would be to evaluate a 250 sq ft system to
see if it is more or less cost effective than the 200 sq ft system. Also a
given system can usually be made more cost effective by installing insulation
to reduce the building heat loss rate. This should always be considered. A
graph of SIR vs collector area would pinpoint the optimum SIR and collector
4.1.1 Example 1 - worksheets.