Tips for Successful Solar Hot Water Installations

By Rick Gilbert, Special to Solar Power World


Installing a solar hot water system presents its own unique set of challenges, and those inexperienced to SHW can get into trouble quickly by not following a few simple best practices.

Throughout recorded history humans used either fire or the sun to heat water. Some communities now have solar water in over 90% of their homes. SHW is often the “forgotten solar” among many professionals nowadays, as PV prices continue to fall and more people are drawn toward the appeal of generating their own electricity. Nonetheless, SHW represents the largest solar market on Earth, and is an affordable alternative to PV that is reliable, environmentally friendly and saves people money.

The average SHW system is the equivalent of a 2-kW PV system. Consumers qualify for the 30% tax credit and many utilities offer additional incentives on top of that. Utilities are traditionally friendlier toward SHW than its PV cousin, partially because SHW’s built-in storage helps reduce morning peak loads (especially in the winter months). SHW is generally viewed as the least costly way to reduce an electric bill. Depending on whether a family lives in a warmer or colder climate, systems range from $5,000 to $7,500, with full payback averaging four years.

Installing a SHW system presents its own unique set of challenges. Those inexperienced to SHW can get into trouble quickly by not following a few simple best practices. Some simple tips for quality installations are as follows:

  • You will need a well-rounded crew that is familiar with roofing, plumbing and light electrical work.
  • Whenever possible, mount the collectors in portrait orientation, not landscape. Most are designed with the risers inside running lengthwise allowing for easy draining and eliminating riser sag that can cause freeze damage. This is a critical mistake often made by new installers.
  • Do not mount too low down into the eaves area of the roof. This area is very difficult to reach from inside the attic space and can cause the installer to have to run plumbing lines outside of the house.
  • The tendency is to think of lowering the high limit on the differential controller. In reality, this is the opposite of what should be done, especially in warmer climates. SHW works very well, so the water coming out of the collector can be extremely hot. Raising the high limit keeps the water circulating, which reduces the chances of melting freeze valves or blowing pressure relief valves. A mixing valve or anti-scald valve should also be installed in these situations.
  • Install the appropriate kind of system for the region. There are several different kinds of SHW systems. Become familiar with words like active, passive, drain back and evacuated tube. Sometimes companies get caught up in using a single product for every application. This is completely wrong and can cause problems later. Always check with the local utility to see if they require a certain type of installation in to qualify for rebates.

The average residential system can be installed by two workers in about one day. Many contractors like these jobs because they are easier to finance, quick to install and can generally get paid the same day. Typically, your phone rings and the customer on the end states they “want to go solar.” Most of the time, this can be translated to “I want to save money.” SHW gives homeowners a less expensive alternative to PV. It reduces the homeowner’s utility bill by saving electricity versus creating it.

As solar has become more mainstream, new advances in technology are revolutionizing the industry. For instance, there are newer polymer collectors that prevent corrosion. Currently, there is movement toward PV-to-tank hot water systems that completely eliminate the SHW collector, something a solar electric contractor should find very appealing. If you’re strategizing new ways to grow your solar business and add to your existing product line, SHW may be the answer you’ve been seeking. SHW will not only help you gain new customers, it gives you another reliable product to go back and sell to your existing customers, helping them save even more money and further reduce carbon emissions. SPW

Rick Gilbert is Executive Vice President of Florida-based Solar Source, a SPW Top 400 Contractor specializing in residential, commercial and industrial projects.