Solar water heating systems for homes are used to produce hot water for showers, washers, sinks, and dishwashers. Technical advances in the last two decades have made solar collectors much more efficient and less costly, than the systems installed in the 70s. Considering the increased cost of fuel and adding the available federal tax credits, makes a solar hot water system affordable for many. Remember though that your system must provide at least 50% of your hot water requirement in order to qualify for the tax credits.

Domestic solar water heating systems are either an open loop system or a closed loop system. Open loop systems are used in regions where temperatures don’t drop below freezing and where the water is soft. The domestic water loop is open to the solar collectors in these systems, and the incoming cold water is run directly through the solar collectors and from there to the solar storage tank. In a closed loop system, the domestic water is isolated from the solar collector loop by a heat exchanger. The liquid running through the collector loop is freeze proof and is usually a glycol solution. Unfortunately, the closed loop systems required in colder areas and regions with hard water, cost more because of the added heat exchanger.

The type of solar collectors you select to install will determine the number and size of the solar collectors, for a given hot water demand. The two most common types are the flat plate collectors and the evacuated tube collectors. Evacuated tube collectors have a higher efficiency and are recommended for colder climates and areas with a high number of cloudy and overcast days. These collectors however, are also more costly. An analysis of cost versus improved efficiency and output, can help you decide which type of collectors to use.

It is important to know that a solar water heating system needs to have a regular water heater as a backup to make sure that you have enough hot water during, and after, a number of days of cloudy weather. I like to look at a residential solar water heating system as a system that PRE-heats the incoming cold water on most days and on some days it heats all your hot water up to the required 130degF. The water heated in the solar collectors is stored in the solar storage tank from where it flows into your regular water heater to be fully heated as needed. With a well designed system, enough hot water will be produced in the solar collectors on clear days so that you don’t need the regular water heater.

I assume you will put the solar collectors somewhere on the roof of your home. The location of the collectors is probably the most important decision you will make. Not enough direct sunlight will result in unsatisfactory system performance. Choose well! If you need someone to help you, call a local solar system installer (they just might do a free analysis for you), or buy/rent a solar radiation tool and do it yourself. Make sure you include any trees that shade your roof.

Once you have determined where on the roof you want to install the solar collectors, talk to a contractor about the requirements for re-inforcements necessary to mount the collectors and frames. Also ask the contractor about the roofing. Several roof penetrations will have to be made. These must be sealed at the end to keep your roof absolutely waterproof.

Ok, let’s move into the house. Here you will need space for the solar storage tank, pump and maybe a small expansion tank, if you will have a closed loop system. How much space? For initial planning purposes, allow at least 2 1/2 times as much space as your existing water heater uses. This needs to be right next to the water heater. Allow enough space for easy access for maintenance.

All right, the collectors are on the roof, the solar storage tank is in the basement. How will the pipes be run between the two? You will need to run two 3″ pipes. That is based on 1″ pipes with 1″ insulation. Scout out which walls you can use to run the pipes up through, all the way from the basement, or first floor, to the roof. If possible, avoid having to build pipe enclosures. That gets costly and might not look very nice. Corners in built-in closets are great places to tuck a set of pipes into.

Done. At least with a lot of the important initial research. Use the knowledge you will have gained after answering all the questions raised. You are now in a good position to either know what else you need to know to be able to design and install a solar hot water system for your home yourself, or hire a contractor for the work.

Avoid the mistakes others have made in the past when they were designing and installing a solar hot water system. Get educated and learn how to plan and prepare for a successful system.