Tankless vs Tank Water Heaters: Which Fits Your San Diego Home?

How do the two designs differ?

A tank, or storage, heater keeps a fixed volume of water hot at all times. When you open a tap, hot water leaves the top and cold water enters the bottom to be reheated. Because the tank sits hot even when nobody is using it, some heat is lost through the walls. The Department of Energy calls this standby loss.

A tankless heater has no reservoir. Water passes through a heat exchanger only when a tap is open, and a gas burner or electric element heats it on the spot. That removes standby loss but limits how much hot water the unit can produce at one time.

How do they stack up?

The energy cost overlap in that table is worth noting. Real savings depend on how much hot water you use and whether the unit is sized and installed well.

Does tankless really save energy?

It depends heavily on household use. The Department of Energy estimates that for homes using 41 gallons of hot water a day or less, a tankless heater can be 24 to 34 percent more energy efficient than a conventional tank. For households that use a lot of hot water, around 86 gallons a day, the gain drops to 8 to 14 percent.

The DOE also warns that a gas tankless model with a standing pilot light can give back part of those savings. If you go tankless, look for a model with an intermittent ignition device rather than a pilot that burns all the time.

In short, a small household that uses modest amounts of hot water sees the strongest percentage savings, while a large family gains less per gallon but uses more gallons overall.

Can one unit keep up with your household?

A tank heater runs out when the stored hot water is used up. A tankless heater never runs out, but it can only heat so many gallons per minute. The DOE notes typical output of 2 to 5 gallons per minute, with gas units producing higher flow than electric ones. Run a shower and the dishwasher at once and a single undersized unit may not keep up.

Sizing is about peak demand, not tank volume. List the fixtures your household might run at the same time on a busy morning and add up their flow rates. The DOE suggests that homes with heavy simultaneous use can install two tankless units or a separate unit for a heavy-use appliance, while noting that extra units add cost and may not be worth it. HomeGuide lists small point-of-use units at $150 to $250 each for a single fixture, such as a far-off bathroom.

What does hard water mean for a tankless heater?

This is the San Diego-specific issue. The City of San Diego's 2025 water quality report lists average total hardness of roughly 14 grains per gallon at its treatment plants. Helix Water District reports about 12 grains per gallon for its plant water, and Escondido reports an average of 215 mg/L.

In a tank, minerals settle as sediment at the bottom. In a tankless unit, they build up as scale inside the narrow passages of the heat exchanger, which cuts efficiency and can trigger error codes or shutdowns. Regular descaling is part of owning a tankless heater here. HomeGuide describes the process as draining the unit and circulating a solution of half white vinegar and half water through it before flushing with clean water, and lists professional tankless flushing at $75 to $300.

A whole-house water softener slows scale buildup in either type of heater. For the bigger picture on local mineral levels, read how hard water affects San Diego homes.

What does switching from a tank cost?

Replacing a tank with another tank is usually a swap. Replacing a tank with a tankless unit is a small project, because the new heater needs different gas supply, venting or electrical service. HomeGuide's 2026 figures for a conversion include:

• Installation labor: $600 to $2,500, often three to ten hours.
• Gas line upgrade: $350 to $750, or up to $2,000 for a new line.
• New venting: $100 to $600, since old tank vents cannot be reused.
• Dedicated electrical circuit for electric models: $250 to $900, plus $850 to $1,700 if the panel needs replacing.
• Permits: $50 to $200.

Gas tankless models often need a larger gas line than the old tank used. If that is part of your plan, see gas line work in San Diego. For a full picture of plumbing prices in the area, the San Diego plumber cost guide lays out typical fees.

What permit will you need?

In the City of San Diego, a standard tank replacement on a non-historic home can go through the online No-Plan Plumbing/Gas Permit. Tankless units are specifically excluded from that path, so expect a Plan permit instead. Elsewhere in the county, rules differ by city. Escondido's permit exemption guideline exempts only minor repairs such as clearing stoppages or fixing leaks, so heater installs there need a permit; the Escondido tankless page has local details. In unincorporated communities, the County of San Diego's Building Division handles permits.

Whichever type you choose, California law requires residential water heaters up to 120 gallons to be braced or strapped against earthquakes, under Health and Safety Code section 19211.

When does a tank still make sense?

• You need a replacement today and want the fastest, simplest install.
• Your budget does not cover a gas line, venting or electrical upgrade.
• You expect to sell the home within a few years and will not recover the extra cost.
• Your household often runs several hot fixtures at once and a single tankless unit would be undersized.

For many households replacing a failed heater on short notice, a new tank is the practical choice. The repair or replace guide helps if you are not sure the old one is finished yet, and the tank replacement page covers the install.

When is tankless the better pick?

• You plan to stay in the house long enough to benefit from the longer service life.
• Your garage or closet space is tight, since a wall-hung unit frees floor area.
• Your hot water use is moderate and spread out during the day.
• You are willing to descale the unit on schedule.

If those fit, start with the tankless water heater page. Buying a home with an existing tankless unit? A plumbing inspection can check its condition and maintenance history before you close. Homeowners in North County can also look at plumbing help in Carlsbad.

Gas safety comes first

With either type, a gas smell means leave the house before anything else, then call 911 and SDG&E at 1-800-611-7343 from a safe place. Homes that use propane, or are all-electric, should check their bill to see which utility supplies them. The what to do if you smell gas guide has more detail.