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  • WATER HEATER EFFICIENCY - CONTENTS: Hot Water Heater Efficiency Ratings, Factors, Improvements. Eficiency of different methods of producing domestic hot water. Recommendations that can cut hot water heating bills significantly
  • POST a QUESTION or READ FAQs about the efficiency ratings of different water heating methods & how to improve water heating efficiency or reduce hot water heating costs
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Water heater energy efficiency comparisons: this article describes and compares the energy efficiency or operating costs of different types of water heater systems.

We list methods for improving water heater efficiency and hot water usage, the efficiency of how we use hot water, and how to reduce the contribution of hot water heating cost to the total building energy bill.

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Hot Water Heater Efficiency Ratings, Factors, Improvements

Article Contents

A Quick Comparison of Water Heater Types by Efficiency

By 2010, according to the American Council for an Energy-Efficient Economy, water heater efficiencies could be organized and described by an energy efficiency factor. Water heater types are listed below in order of overall energy efficiency as follows:

Table of Water Heater Energy Efficiency Ratings

Energy source - fuel Type of water heater Energy Efficiency Rating - EF
Oil, No.2 home heating oil Conventional oil fired water heater 0.55
Gas, LP or Natural Conventional gas fired water heater 0.60
Gas, LP or Natural High efficiency gas fired water heater 0.65
Gas, LP or Natural Pilotless gas fired water heater 0.80
Gas, LP or Natural Condensing gas storage type water heater 0.86
Electricity Minimum-efficiency electric storage type water heater 0.90
Electricity HIgh efficiency electric storage type water heater 0.95
Solar Solar water heater, electric backup 1.20
Electricity Electric heat pump water heater 2.20

Notes to the table:

1. The energy efficiency ratings do not reflect water heater recovery times. For example, an electric storage tank type water heater will generally have a slower recovery time than a gas fired or oil fired heater of similar size.

See WATER HEATER COMPARISONS, PROPERTIES for a description of water heater life expectancy, recovery rates, costs and operating costs, and a comparison of other water heater types and properties.

2. Data sources [1] [2] [3] [4]

3. As we explain below, the local efficiency of a water heater may look great, but the true energy efficiency of a water heater depends on more broad considerations. For example, electric resistance heating is only as clean and efficient as the fuel (often coal) used at the electrical company's power plant. The cost, efficiency, and environmental impact of the fuel used at the electrical generating plant that powers your electric heater varies widely by geographic area.

4. Also see ENERGY STAR PROGRAM

Solar water heater (C) Daniel FriedmanBut, currently (2012) unless your electric utility company is offering preferential electricity rates (such as off-peak energy use or an "all electric home" discount), even though modern electric water heaters have a higher efficiency factor than oil or gas fired water heaters, don't assume that an electric water heater is the most sound environmental choice.

These energy efficiency factor ratings do not include variations in life expectancy of the water heater, but ACEEE rated all of the water heaters at an expected 13-year life except oil-fired that they rated at 8 years.

The shorter life of the oil fired equipment, combined with its lower EF (if these are accurate estimates) mean that the per-year operating cost of oil fired water heating equipment is more than its competitors. These ratings also do not compare BTUH input rates of the different equipment and thus don't say anything about the hot water recovery rate.

Also, the purchase and install costs of these different types of water heating systems vary widely, from a low of $820. for a typical high-efficiency electric storage type (tank) water heater, to $4,800. for a solar water heater with electric backup. Costs do not include installation labor nor the effect of financial incentives, to this cost for solar hot water is over-stated.

Hot Water Usage Efficiency Improvements You Can Make

Water heater timer control (C) Daniel FriedmanOften efficiency improvements in hot water use (or production) include include recommendations for installing restrictions on the flow rate of hot water in a building (flow restrictors or restrictors combined with an anti-scald valve), either right at the fixtures, or at the water heating device. You are trading off total flow rate for reduced water heating costs.

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