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Tankless vs tank water heater: how to choose
A tank water heater costs less upfront and is the simplest swap. A tankless unit gives continuous hot water, saves space and, per the U.S. Department of Energy, can be 24% to 34% more efficient for homes using up to about 41 gallons a day. Heat pump tanks are a third option worth pricing.
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Quick answer: tankless vs tank at a glance
| Tank (storage) | Tankless (demand) | |
|---|---|---|
| Installed cost (US) | $1,200–$2,300 (This Old House, "How Much Does Water Heater Installation Cost?" (updated 06/17/2026; Home Depot data)) | $2,100–$4,000 (This Old House, "How Much Does Water Heater Installation Cost?" (updated 06/17/2026; Home Depot data)) |
| Efficiency | Standby heat loss | 24%–34% more efficient at up to ~41 gal/day (U.S. DOE Energy Saver, "Which Water Heater Is Right for You?") |
| Typical life | 10–15 years (U.S. DOE Energy Saver, "Which Water Heater Is Right for You?") | 20+ years (U.S. DOE Energy Saver, "Which Water Heater Is Right for You?") |
| Hot water supply | Limited by tank size | Continuous, limited by flow rate |
| Space | Floor space for the tank | Wall-mounted |
| San Diego permit | Simple no-plan permit in City of SD | Plan-required permit in City of SD (City of San Diego, Plumbing/Gas Permit) |
How each type works
Storage tank
A tank keeps 40–80 gallons hot and ready, so it loses some heat while it sits.
Tankless
A tankless unit heats water only when a tap opens, so there's no standby loss, but output is limited by flow rate when several fixtures run at once.
Heat pump water heaters
Heat pump (hybrid) tanks move heat from the air into the water. This Old House lists them at $2,500–$3,500 installed (This Old House, "How Much Does Water Heater Installation Cost?" (updated 06/17/2026; Home Depot data)).
Cost comparison
See the replacement cost guide for sourced national and San Diego prices.
Pros and cons of tankless water heaters
- + Continuous hot water and longer life (U.S. DOE Energy Saver, "Which Water Heater Is Right for You?")
- + Saves floor space
- − Higher upfront cost, and retrofits may need gas line, venting or electrical upgrades (This Old House, "How Much Does Water Heater Installation Cost?" (updated 06/17/2026; Home Depot data))
- − In the City of San Diego, needs a plan-required permit (City of San Diego, Plumbing/Gas Permit)
Pros and cons of tank water heaters
- + Lowest upfront cost and simplest like-for-like swap
- + Simple no-plan permit in the City of San Diego
- − Shorter life and standby heat loss (U.S. DOE Energy Saver, "Which Water Heater Is Right for You?")
- − Needs floor space and earthquake strapping (California Health & Safety Code §19211 (water heater bracing))
California and San Diego install considerations
Gas line and venting for tankless retrofits
Gas tankless units need enough gas supply and proper venting; budget for upgrades if your current line is sized for a tank (This Old House, "How Much Does Water Heater Installation Cost?" (updated 06/17/2026; Home Depot data)).
Permits and seismic strapping
Tanks must be braced or strapped under state law (California Health & Safety Code §19211 (water heater bracing)).
Rebates
TECH Clean California single-family heat pump water heater incentives have been reserved statewide since November 14, 2025 (TECH Clean California, Single-Family Incentives). Check SDG&E for current offers (SDG&E Rebates).
Which should you choose?
- Tight budget or an urgent failure: a like-for-like tank.
- Staying many years with moderate hot water use: price a tankless.
- Electric home with garage space: price a heat pump tank.
- Large household running several showers at once: ask about tank size or tankless flow rate.
Compare license-checked San Diego pros
See each pro's CSLB license, bond and workers' comp, then call 2 or 3 for written quotes. It is free.
VettedHeater may be paid by some pros in the future. Payment never affects which pros we list or the order they appear in.
FAQs
Is a tankless water heater worth it?
For households using up to about 41 gallons of hot water a day, DOE says demand water heaters can be 24% to 34% more energy efficient than conventional storage heaters. Upfront cost is higher, so it depends on how long you'll stay and your hot water use.
How long does a tankless water heater last vs a tank?
DOE's Energy Saver guide puts most tankless units at more than 20 years and storage tanks at 10 to 15 years.
Can I switch from tank to tankless in San Diego without upgrading my gas line?
Sometimes not. Tankless retrofits often need gas line, venting or electrical upgrades. Ask your installer to check gas capacity.
Do tankless water heaters need a permit?
Yes. In the City of San Diego, tankless replacements are excluded from the simple no-plan permit and need a plan-required Plumbing/Gas Permit.
Sources
- U.S. DOE Energy Saver, "Which Water Heater Is Right for You?" (checked October 22, 2026)
- This Old House, "How Much Does Water Heater Installation Cost?" (updated 06/17/2026; Home Depot data) (checked October 22, 2026)
- City of San Diego, Plumbing/Gas Permit (checked October 22, 2026)
- California Health & Safety Code §19211 (water heater bracing) (checked October 22, 2026)
- TECH Clean California, Single-Family Incentives (checked October 22, 2026)
- SDG&E Rebates (checked October 22, 2026)