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AGE of WATER HEATERS
ALTERNATIVE HOT WATER SOURCES
ANODES & DIP TUBES on WATER HEATERS
ANTI SCALD VALVES
APPLIANCE EFFICIENCY RATINGS
AQUASTAT CONTROL Functions
BACKDRAFTING HEATING EQUIPMENT
BACKFLOW PREVENTER, HEATER WATER FEEDER
CARBON MONOXIDE - CO
CHECK VALVES, WATER SUPPLY
CLOGGED SUPPLY PIPING
CROSS CONNECTIONS, PLUMBING
DEBRIS in WATER SUPPLY, Water Heater
DRAIN a WATER HEATER TANK
ELECTRIC WATER HEATERS
FLOODED WATER HEATER REPAIR
FREEZE-PROOF A BUILDING
GALVANIC SCALE & METAL CORROSION
GAS BURNER Flame & Noise Defects
GAS FIRED WATER HEATERS
GAS PIPING, VALVES, CONTROLS
HEATING COST SAVINGS METHODS
HOT WATER SUPPLY
HOT WATER IMPROVEMENTS
HOT WATER DELIVERY SPEED UP
HOT WATER EFFICIENCY IMPROVEMENT
HOT WATER PRESSURE EXPANSION RATE
HOT WATER PRESSURE LOSS
HOT WATER PROBLEM DIAGNOSIS
HOT WATER QUANTITY IMPROVEMENT
HYDROGEN SULFIDE GAS
INDIRECT FIRED WATER HEATERS
MANUALS & PARTS GUIDES - HVAC
MIXING / ANTI-SCALD VALVES
NO HEAT - NO HOT WATER: HEATER DIAGNOSIS
NOISE, WATER HEATER
ODORS IN WATER
PIPING IN buildings, Clogs Leaks Types
RELIEF VALVE LEAKS
RELIEF VALVES - Water Heaters
SCALE REMOVAL, WATER HEATERS
SEWER GAS ODORS
SOLAR HOT WATER HEATERS
TANKLESS WATER HEATERS
THERMAL EXPANSION of HOT WATER
THERMOSTATS, WATER HEATER
TIMERS for ELECTRIC WATER HEATERS
WATER HEATER ALTERNATIVES
WATER HEATER ANODES, DIP TUBES
WATER HEATER AIR INLET
WATER HEATER DEBRIS FLUSH
WATER HEATER DRAIN PROCEDURE
WATER HEATER EFFICIENCY
WATER HEATER FLUSH PROCEDURE
WATER HEATER NOISES
WATER HEATER PROBLEM DIAGNOSIS
WATER HEATER PROPERTIES
WATER HEATER SCALE
WATER HEATER SAFETY
WATER HEATERS for HOME HEATING USE?
WATER ODORS, CAUSE CURE
WATER PIPES, Clogs Leaks Types
WATER PRESSURE TOO HIGH: DANGERS
WATER PRESSURE LOSS DIAGNOSIS & REPAIR
WATER QUANTITY IMPROVEMENT
WATER SOFTENERS & CONDITIONERS
WINTERIZE A BUILDING
Hot water heater properties: this article describes how to compare the operating characteristics such as safety, capacity, life expectancy, and operating cost of alternative methods of providing domestic hot water for washing and bathing.
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Thanks to Carson Dunlop, a Toronto Home Inspection Firm and Home Inspection Educator, for permission to use sketches shown in this article.
This article on water heater characteristics describes and compares the following properties of different kinds of water heating systems and appliances:
Water Heater Life Expectancy Comparisons
The following articles discuss alternative ways to produce domestic hot water for washing and bathing.
Here is a rough guess at the relative life expectancy of these types of water heaters, provided all other water heater life factors (discussed at AGE of WATER HEATERS) are the same (comments are invited Contact Us) - water heaters are listed in their order of typical life from shortest to longest:
Conditions Affecting Water Heater Life
Keep in mind that conditions besides the type of water heater can dominate its life expectancy. Some of these water heater life expectancy factors include:
For complete information about water heater life and things that affect how long a hot water heater will last, see our full article at AGE of WATER HEATERS.
How to Evaluate the Present and Future Relative Operating Cost of Different Types of Water Heaters: definition of therms
In the U.S. natural gas is sold to consumers sometimes measured in therms (th). Therms is also used in Energy Guide ratings useful for comparing alternative water heater operating costs.
A therm is the amount of natural gas used to generate 100,000 BTUs of energy.
A therm (th) is thus also a measure of heat content, or a measure of energy usage.
Since this is a simple fixed number, it's easy to compare gas-fired water heater efficiencies.
Example: If water heater A uses 1 therm to produce 100 gallons of hot water heated up from 40 degF to 120 degF, and water heater B uses 2 therms to produce the same 100 gallons of hot water heated up from 40 degF to 120 degF, then water heater A will cost half as much to operate as water heater B. In other words, the fewer therms/gallon or therms/estimated-annual-usage-in-gallons, the higher is the efficiency and lower the operating cost of a given water heater.
In order of cost from least-costly to most-costly to purchase and maintain we estimate this order of types of water heater:
Hot Water Quantity: A Comparison of the Relative Total Hot Water Capacity of Different Types of Water Heaters
Any water heating method that stores hot water in a tank will provide about the same total hot water capacity if the tank is the same size. This includes electric, gas, oil fired water heaters and side-arm coil water heaters or range boilers, all of which use a water storage tank.
Instantaneous water heaters, also called tankless water heaters, can provide effectively endless hot water but usually in limited quantity to the one or two fixtures supplied by the heater.
Tankless coils provide a more limited quantity of hot water, depending on the amount of heat stored in the heating boiler (a function of its size and materials of construction - steel has less heat storage than cast iron), the temperature of the incoming water, the use of mixing valves, and the flow rate through the coil.
Most tankless coils are rated as capable of providing a specific temperature degree rise across the coil, from input to output, at a specified boiler temperature and at a specified water flow rate in gallons per minute (often 5 gpm). If the water flow rate is faster than specified the coil will not heat water to as high a temperature.
Relative Hot Water Recovery Rate/Speed of Different Types of Water Heaters - What is the recovery rate of a water heater?
As we illustrate with Carson Dunlop's sketches shown here, in order of speed of re-heating or hot water recovery time, listing slowest-recovery time to fastest recovery time we'd list water heater types as follows:
Don't confuse water heater recovery rates (how fast we can heat water) with water heater operating costs, which we discuss at Water Heater Operating Cost Comparisons. Recovery rate is measured in gallons per hour or gph. Water heater operating costs are compared using a standard measure of energy cost in therms.
See our complete list of water heater safety features and devices found at WATER HEATER SAFETY.
Most critical in determining the safety of any water heater is that the heater is properly installed and includes the required safety controls such as those responsible for limiting temperature and pressure. Any water heater should include a temperature and pressure relief valve installed of the proper type and at the correct location. Gas-fired devices also should include flue-gas spillage detectors. Oil-fired devices should also include a fire-safety valve that shuts off fuel to the appliance in case of fire.
We guess that proper installation, inspection, and maintenance make more difference in the safety of a water heater than the innate differences among heater types, fuels, etc.
Some Hot water heater safety devices and features
See our complete list of water heater safety features and devices found at WATER HEATER SAFETY. Excerpts are below.
Frequently Asked Questions (FAQs)
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Technical Reviewers & References
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