Tankless water heaters typically last 15 to 20 years with proper maintenance, and some units can operate for more than 20 years. The actual lifespan depends on water quality, maintenance, installation, proper sizing, household hot water use, and the condition of components such as the heat exchanger.
Quick Takeaways
Tankless water heaters typically last 15 to 20 years.- Well-maintained tankless units can sometimes last 20 years or longer.
- Hard water and mineral buildup can shorten water heater lifespan.
- Regular maintenance can help extend the life of the system.
- Proper installation and sizing affect long-term performance.
- Frequent repairs, leaks, temperature problems, and recurring error codes can indicate an aging tankless water heater.
How Long Does a Tankless Water Heater Last?
A tankless water heater typically lasts 15 to 20 years with proper care. Some well-maintained tankless units can operate for more than 20 years. Traditional tank water heaters usually last about 8 to 12 years, giving tankless systems a longer typical life expectancy.
Tankless water heaters work differently from traditional tank water heaters. A tank-style system keeps stored water hot until someone needs it. A tankless water heater heats water on demand as water moves through the unit.
Tankless design alone does not guarantee a 20-year lifespan. Water quality, maintenance, installation, sizing, and household demand all affect how long a tankless water heater lasts.
What Affects the Lifespan of a Tankless Water Heater?
Water quality, maintenance, installation, sizing, and household hot water use can all affect tankless water heater lifespan. Proper care can help a tankless unit reach its expected service life. Scale buildup and unresolved mechanical problems can shorten it.
Water Quality and Mineral Buildup
Hard water can shorten tankless water heater lifespan by causing mineral buildup inside the unit. Minerals in the water can form scale on the heat exchanger and other internal surfaces.
The heat exchanger transfers heat to water as the water passes through the system. Scale can interfere with that heat transfer and reduce performance.
Water quality can therefore affect both maintenance needs and long-term reliability. Homes with hard water may need more frequent descaling based on the water heater manufacturer’s recommendations.
Maintenance
Regular maintenance can help a tankless water heater reach its expected 15- to 20-year lifespan. Flushing and descaling are especially important when mineral buildup develops inside the water heater.
Tankless water heater maintenance can include:
- Flushing or descaling the system
- Cleaning applicable water filters
- Inspecting water and gas connections
- Checking the burner on gas models
- Inspecting the venting system
- Checking for leaks, corrosion, or error codes
Annual flushing is commonly recommended for many tankless units, but maintenance requirements vary. Water quality, usage, and the manufacturer’s instructions should determine the maintenance schedule.
Installation Quality
Proper installation helps a tankless water heater operate within the manufacturer’s specifications. Poor installation can create performance problems and place unnecessary stress on the water heating system.
Depending on the model, tankless water heater installation may require the correct:
- Gas supply
- Electrical capacity
- Venting
- Water pressure
- Water connections
- Drainage
- Equipment clearances
Gas and electric tankless water heaters have different installation requirements. The manufacturer’s installation instructions should be followed for the specific unit.
Tankless Water Heater Size
Proper sizing helps a tankless water heater meet peak hot water demand without being routinely overloaded. An undersized tankless unit may struggle when several showers, faucets, or appliances require hot water at the same time.
Tankless water heater sizing is based primarily on flow rate and temperature rise. Flow rate measures how many gallons of hot water the home needs per minute. Temperature rise measures how much the incoming cold water must be heated to reach the desired temperature.
If you’re choosing a new system, learn what size tankless water heater you need based on your home’s flow rate, temperature rise, and simultaneous fixture use.
Household Hot Water Usage
Heavy hot water demand can increase how often and how long a tankless water heater operates. Higher usage means burners, heat exchangers, valves, and other components spend more time working.
Tankless units heat water on demand rather than keeping stored water hot. A large household that frequently runs several hot water fixtures at once can place greater demand on a tankless system than a smaller household with staggered usage.
Proper sizing helps the water heater handle that demand as designed.
How Can You Make a Tankless Water Heater Last Longer?
Regular maintenance and early repairs are two of the best ways to extend the life of a tankless water heater. Preventing heavy scale buildup and addressing performance problems early can reduce unnecessary stress on the water heating system.
To help a tankless water heater last longer:
- Follow the manufacturer’s maintenance schedule: Service requirements can vary by brand and model.
- Address hard water and mineral buildup: Scale can collect on the heat exchanger and reduce heat transfer.
- Flush the system when recommended: Flushing or descaling removes accumulated minerals from the water heater.
- Clean applicable filters: Clogged inlet filters can restrict water flow.
- Keep vents clear on gas models: Gas tankless water heaters need proper airflow and exhaust venting.
- Repair leaks promptly: Small leaks can damage components and surrounding materials.
- Investigate recurring error codes: An error code identifies a condition that may need service.
- Maintain appropriate water pressure: Excessive water pressure can put unnecessary stress on plumbing components.
- Have recurring problems diagnosed: Repeatedly resetting a malfunctioning water heater does not fix the underlying problem.
Proper care does not guarantee a specific lifespan. It does give the heat exchanger and other components better conditions to operate as designed.
What Are the Signs a Tankless Water Heater Is Wearing Out?
Frequent repairs, inconsistent hot water, leaks, recurring error codes, and declining performance can indicate that a tankless water heater is wearing out. One symptom does not automatically mean the unit needs replacement, but repeated problems deserve professional diagnosis.
Common warning signs include:
- Inconsistent hot water: The water repeatedly becomes hotter or colder than expected.
- Reduced hot water flow: The tankless water heater no longer delivers its previous flow rate.
- Recurring error codes: The same fault returns after resetting or servicing the unit.
- Unusual noises: New sounds can point to mineral buildup or a mechanical problem.
- Leaks: Water around the tankless unit can indicate a failing connection or internal component.
- Corrosion: Visible corrosion can indicate deterioration around connections or components.
- Frequent repairs: Several repairs within a short period can signal an aging system.
- Declining performance: The water heater increasingly struggles to meet normal household hot water demand.
Mineral buildup, clogged filters, ignition problems, and other repairable issues can cause similar symptoms. A plumber can diagnose the problem before deciding that the tankless water heater has reached the end of its life.
Should You Repair or Replace an Older Tankless Water Heater?
An older tankless water heater does not automatically need replacement just because it reaches 15 or 20 years. The water heater’s condition, repair history, performance, parts availability, and current repair cost matter more than age alone.
Repair can make sense when the problem involves a replaceable component and the rest of the water heater remains in good condition. A 15-year-old unit that has received proper care may still have useful service life remaining.
Replacement becomes more practical when:
- Repairs are becoming frequent.
- A major component has failed.
- The heat exchanger is damaged or leaking.
- Replacement parts are difficult to obtain.
- The unit has significant corrosion.
- The water heater can no longer meet normal hot water demand.
- The cost of repair is difficult to justify for the age and condition of the unit.
A newer tankless water heater may also offer better energy efficiency than an older model. However, age by itself is not a reason to replace a tankless system that still operates safely and reliably.
FAQs
Can a Tankless Water Heater Last 20 Years?
Yes. A tankless water heater can last 20 years, and some well-maintained units operate longer. A.O. Smith lists a typical tankless water heater lifespan of about 15 to 20 years and notes that properly maintained units can last beyond 20 years.
Water quality, maintenance, installation, sizing, usage, and component condition all affect whether a specific water heater reaches or exceeds 20 years.
Can a Tankless Water Heater Last 30 Years?
A tankless water heater can potentially remain operational for 30 years, but 30 years is longer than the typical life expectancy. Homeowners should generally expect about 15 to 20 years rather than assuming every tankless unit will reach 30 years.
A very long service life depends on the specific equipment, water quality, maintenance history, operating conditions, repairs, and availability of replacement parts.
Do Gas or Electric Tankless Water Heaters Last Longer?
Gas or electric power alone does not determine tankless water heater lifespan. Equipment quality, installation, maintenance, water quality, usage, and operating conditions can have a major effect on how long either type lasts.
The manufacturer’s expected service life and maintenance requirements provide a better comparison than fuel type alone.
Does Hard Water Shorten a Tankless Water Heater’s Lifespan?
Yes. Hard water can shorten tankless water heater lifespan when mineral buildup is allowed to accumulate inside the system. Scale can collect on the heat exchanger and reduce the system’s ability to transfer heat efficiently.
Regular descaling can help control mineral buildup. Homes with hard water may require more frequent maintenance based on the manufacturer’s recommendations.
How Often Should a Tankless Water Heater Be Serviced?
Tankless water heater maintenance should follow the manufacturer’s recommended schedule. Many systems receive annual service or flushing, but water quality, usage, and the specific model can change how often maintenance is needed.
Hard water can increase scale formation and may require more frequent descaling. The owner’s manual for the specific tankless water heater should provide the starting maintenance schedule.
Is It Worth Repairing a 15-Year-Old Tankless Water Heater?
A 15-year-old tankless water heater can be worth repairing when the repair is relatively minor and the rest of the unit remains in good condition. Fifteen years falls within the normal life expectancy of many tankless water heaters.
Repair history, parts availability, heat exchanger condition, performance, and repair cost should all be considered. Replacement may make more sense when an older unit requires repeated or expensive repairs.
Get More Years From Your Tankless Water Heater
Proper maintenance and timely repairs can help a tankless water heater provide reliable hot water for many years. Apollo Plumbing can inspect an aging system, diagnose performance problems, perform needed maintenance, and help determine when replacement makes more sense than another repair.
For professional tankless water heater service in Everett, WA, contact Apollo Plumbing for help with tankless water heater maintenance, repair, installation, and replacement.
