Tankless heaters last longer and never run out mid-shower when sized right, but cost more to install and need more care in hard water. Here is how they compare for a San Diego home.
| Tank | Tankless | |
|---|---|---|
| Typical lifespan (DOE) | 10–15 years | Up to about 20 years |
| Equipment cost (DOE industry averages, gas) | About $700 | About $1,160–1,760 |
| Hot water supply | Limited by the first-hour rating | Continuous, limited by flow rate (GPM) |
| City of San Diego permit | Simple no-plan permit | Plan-required permit |
| Hard-water maintenance | Flush sediment (Rheem: every 6 months in hard water) | Descale the heat exchanger (Rinnai and Navien: at least yearly) |
Lifespan
The Department of Energy says tankless water heaters are generally considered to last up to 20 years, compared with 10 to 15 years for tank-type heaters.
Upfront cost
Tankless units cost more, and converting from a tank usually adds gas line, venting and electrical work. In the City of San Diego a tankless install also needs a plan-required permit, while a tank swap uses a simpler permit.
Sizing
Tankless heaters are sized by flow rate in gallons per minute and by how much they must heat the incoming water. Undersizing is the most common complaint: lukewarm water when two showers run at once.
Hard water
This is the San Diego-specific part. The City reports its water averages about 16 grains per gallon of hardness. The Department of Energy notes that hard water damages tankless heaters and that, above roughly 8 to 14 grains per gallon, manufacturers may require a water softener to protect the unit. It also recommends flushing anywhere from twice a year to every three years.
The City of San Diego, for its part, says it does not consider a softener necessary for drinking water and notes softened water is more corrosive to plumbing. Weigh both, and check the warranty terms of the unit you are considering.
Common questions
Is tankless worth it in San Diego?
It can be if you plan to stay in the home long enough to benefit from the longer life, and you are prepared for scale maintenance. If you want the lowest upfront cost and simplest permit, a tank replacement is easier.
General information, not professional or legal advice; follow your manufacturer's manual, and your installer and local permit office have the final word. Sources:U.S. Department of Energy, Building America: Transitioning to a Tankless Water Heater; City of San Diego, Plumbing/Gas Permit; City of San Diego, Water Quality (hardness); City of San Diego, Water Quality FAQ. SD Water Heaters is not affiliated with any manufacturer; brand names are used only to identify products, and codes can differ by model, so confirm in your own manual.
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