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How to Buy a Hot Water Heater

Updated June 12, 2014
By

There are two main types of water heaters: units that have an insulated storage tank to hold hot water until it is needed and “tankless” units, which only heat the water as it is needed.

Tankless models tend to be more energy efficient but have lower throughput—that is, produce less hot water in a given amount of time--than models with storage tanks. Both types of water heaters come in versions powered by electricity, natural gas, or liquid propane. In general, electric models cost the most to operate and are the least energy efficient.

Solar water heaters are starting to gain traction in the marketplace. They come in both passive and active configurations and can use several different types of collectors. Currently, solar water heaters are more expensive than other options but are typically cheaper to operate. Solar water heaters depend on line of sight access to sunlight, so carefully evaluate the proposed installation site with a professional before committing to solar.

 

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Hot Water Heater

Water heaters are made by a wide variety of heating and cooling (HVAC) companies, including:

How much Capacity do you Need?

Capacity is an important factor in choosing a hot water heater. To determine how much capacity you need, estimate your home’s water usage during the heaviest hour of a typical day. Typically showers and faucets have a published flow rate that is measured in gallons (or liters) per minute. If you can't find the flow rate, you can measure it yourself:

  1. Get a stop watch and a bucket
  2. Place the bucket under the faucet, and turn it on full blast for 10 seconds
  3. Measure how much water is in the bucket, and convert it to gallons (1 cup = .0625 gallons)
  4. Since you only collected water for 10 seconds, you will need to multiply the number of gallons of water you collected by 6 to determine the gallons per minute.

For example, let's imagine that in 10 seconds, you collected 2.5 cups of water. You would convert that to gallons (2.5 x .0625 = .15625 gallons) for a total of .15625 gallons every 10 seconds. Next, multiply that by 6 to determine the number of gallons per minute (.15625 x 6 = .9375 gallons per minute).

You will need to ask yourself how many faucets and showers you expect to be able to run simultaneously. For most families you might want to be able to use the hot water at the kitchen sink while someone is taking a shower. To determine your estimated total usage, add the flow rate of the shower and the kitchen sink faucet. This will give you a maximum flow rate in gallons per minute.

Multiply the flow rate (in gallons per minute) times 60, to determine the number of gallons per hour you need at the peak hour of the day. This is sometimes known as the "peak hour demand".

Water heaters have a rating called the first-hour rating (FHR) or first-hour delivery that indicates the number of gallons per hour of hot water your water heater can provide. This number should be very close to your peak hour demand.

Tankless heaters generally produce 3.5 gallons per minute. Heavy users will likely find this insufficient.

Before selecting a hot water heater, it is also important to measure tank sizes and the available space in your home. It does no good to purchase a high capacity heater if it doesn't fit into your space. And while it is possible to extend plumbing lines to a different location, that can greatly increase the installation costs.

Another factor to consider is the material used to construct the storage tank in units that use them. Stainless steel tanks are expensive but do not rust. Steel tanks coated in ceramic or porcelain are also resistant to corrosion, unless they are scratched or dented. Tank corrosion may require you to replace the entire unit, while problems such as leaky valves or worn out electrical elements can be fixed with replacement parts.

Water Heater Warranties

Many water heaters come with long warranties (anything from 6 to 12 years) but the majority of these warranties cover only defective parts. For example, GE water heaters come with a full replacement warranty for the first year and a defective parts warranty for an additional 5, 8, or 11 years. Many other brands structure their warranties in a similar manner.

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