Depending on where you live, the solar system may NOT "be on your roof for the nest 25 years". Here, most were gone within 10 years of installation, either because the panels froze and busted, or the storage tank/heater started leaking. In either case, repairs were expensive and therefore the systems were abandoned in favor of a conventional unit. Solar also does not work good with gas water heaters. Solar, like tankless heaters, have their place in the market, but do not overhype them as a panacea for all installations. And, I would hope the person had more than just "some help" because they are NOT a DIY installation.