The document compares the costs and benefits of solar water heating systems versus on-demand water heaters over a 30-year period. It finds that while solar systems have higher upfront installation costs that are about twice as much as on-demand heaters, solar systems provide greater overall savings and return on investment over the long run. Specifically, the analysis shows the solar system providing roughly twice the cumulative savings and a return of 31% compared to 18% for the on-demand heater. However, it notes the optimal choice depends on site-specific factors like solar access and water quality.