Solar Hot Water Heaters: What Size Do You Need? Solar Hot Water Heaters: What Size Do You Need?

Installing a solar hot water heater has gained considerable popularity over the last decade. The main reason why is the potential energy savings a homeowner can enjoy. The use of such hot water heater can save a household up to 25 percent on a monthly electricity bill. It may take a few years to get a return on investment but it is well worth it, not only for the long-run savings but also for the immediate environmental benefits.

How Solar Hot Water Heaters Works

Using solar energy is an easy way to heat an entire household water supply. A glass collector has to be installed on the south side of the roof. It has to be positioned in a way to get as much sun as possible without any obstructions such as trees or shade from other nearby buildings.

A typical type of collector may consist of a ray of copper pipes surrounded by an absorbing plate in an insulated box. The box is covered by glass. The collectors are connected to a storage tank which holds preheated water.

The sun shines through the glass and heats up the plate, usually a copper plate, which is laminated to a heat transfer tubing that carry the  liquid to a heat exchanger such as a water tank. Then that stored heat is used to warm the water inside in the tank.

This system can be integrated in a house using the existent water heating tank. Sometimes an additional water tank is needed to store as much preheated water as possible.

How to Determine the Size Needed

To size the system to be installed most solar hot water heater specialists first look at how many people are living in a household. The rule of thumb is to figure 20 square feet of collectors for every two people living under the roof.

An additional 8 square feet is added for every additional person if the house is located in a sunny climate. If the house is located in a colder, less sunny climate such as Northern United States or Canada, an additional 12 to 14 square feet should be added for every extra person in the household.

Sizing the Storage Tank

The goal is to have a system that meet 90 to 100 percent of the hot water demands in the summer months. For a small family of three people, a small 50- to 60-gallon tank is usually big enough. For a household of three to four people, a medium size tank of 80 gallons is needed to meet the demand. Bigger tanks have to be used for households with more than four people.

Sometimes when the demand for hot water is low, the system can be prone to overheating. The formula to prevent this to happen is 1.5 gallons of storage for every square foot of collector. It is recommended in very sunny areas to increase the formula to 2 gallons of storage per foot of collector.

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