What Hot Water Heater is Best for You?

Ecologically sound solutions for heating your home’s water supply can also save you money.

| March/April 2002

  • The AquaStar Model 125B on-demand (tankless) water heater provides instant energy savings.
    Photo courtsey Gaiam Jade Mountain

Many people are not aware that hot water doesn’t come cheap. Consider this: Over its 13-year lifespan, a $350 electric water heater will cost you more than $5,500 in energy bills and will emit more than 32.5 tons of carbon monoxide. But you don’t have to sacrifice hot showers to live an environmentally conscious lifestyle. Today, you can choose from a variety of efficient water-heating options. Depending on your location and budget, you can find a system to supplement or provide all your hot water needs that uses significantly less (or no) fossil fuel energy.

You may even decide to give your old tank-style system early retirement. In most cases, hot water heaters consume more energy as they get older; for example, a sediment-filled 10-year-old water heater may be running at just 50 percent efficiency.

Sun showers

Solar water heaters are a sound environmental and economic choice. Although they cost more up front—from $1,200 to $4,000—solar systems cost less when you consider annual energy costs and realize that they can outlast two or three tank-style water heaters. The Florida Solar Energy Center (FSEC) has found that solar systems can pay for themselves in four to eight years (and will continue to operate for an additional seven to thirty years). In addition, some state and local governments offer rebates and tax incentives to encourage residents to invest in solar technologies, so check with your local energy office before you buy.

Solar water heaters can be grouped into two subcategories: passive or active. Passive systems have no breakable electric components; consequently, they’re more reliable, easier to maintain, and less expensive. The downside is that they are generally less efficient than active systems, which use electric pumps, valves, and controllers to circulate the heat-transfer fluid through the solar collectors. Because of the extra hardware, active systems are generally more expensive, but they can produce more hot water per square foot of collector space, and can be adapted for areas that are subject to extended freezing temperatures. Active systems are also easier to retrofit on existing homes because the collectors can be located away from the storage tank.

Passive and active solar water heaters can be either “open-loop” or “closed-loop.” Open-loop, or direct, systems circulate household water through the collector. Closed-loop systems circulate water or another heat-transfer fluid (such as antifreeze) through the collectors, then transfer only the stored heat to the water supply through a heat exchanger (double-walled heat exchangers prevent the heat-transfer fluid from mixing with the drinking water). Closed-loop systems are more complex and more costly, but they protect the collectors against freeze damage.

If you live in an area that doesn’t experience hard-freeze winters, the simplest and least expensive solar heating system available is the batch, or “breadbox,” heater. This open-loop, passive system consists of one or more storage tanks within an insulated box. The tanks are designed to absorb solar energy and limit solar loss. Combining the collector and storage tank eliminates pumps, controllers, and wiring. Batch heaters start at about $1,000, but you can build one yourself for as little as $300.

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