Calculate peak GPM demand, BTU input, and temperature rise using Florida's 60β76Β°F groundwater temperatures. Size gas or electric tankless units correctly for FL's unique conditions
FL GROUNDWATER 60β76Β°FEnter the quantity of each hot-water fixture. Peak demand = simultaneous use (e.g., 2 showers + dishwasher running at once).
Low (1β3 GPM): 1 shower + kitchen faucet. Studio, condo, or 1BR apartment.
Moderate (3β5 GPM): 2 showers + dishwasher. Standard FL 3BR/2BA home β most common sizing range.
High (5β8 GPM): 2+ showers + tub fill + dishwasher. Larger home, master bath with rainfall head.
Very High (>8 GPM): Multiple showers + heavy commercial use. Two units or a commercial-grade system.
FL tip: Clothes washers rarely run on hot in Florida's warm climate β most FL residents use cold wash year-round. Don't oversize for the washer unless it's specifically used for hot cycles.
Why FL is ideal for tankless: Florida's warm groundwater (60β76Β°F year-round) means far less temperature rise than cold-climate states (40β50Β°F groundwater). A unit rated for 5 GPM in Minnesota may handle 8+ GPM in South FL at the same BTU input.
No seasonal penalty: Unlike northern states where groundwater drops to 40Β°F in winter and forces oversizing, FL groundwater stays nearly constant year-round. The unit you size for summer is the unit you need in January.
| FL Region | Groundwater | ΞT to 110Β°F | vs. Northern ΞT |
|---|---|---|---|
| South FL | 76Β°F | 34Β°F | 48% less BTU |
| SW FL | 75Β°F | 35Β°F | 46% less BTU |
| Central FL | 72Β°F | 38Β°F | 40% less BTU |
| Space Coast | 70Β°F | 40Β°F | 36% less BTU |
| NE Florida | 67Β°F | 43Β°F | 31% less BTU |
| N Central FL | 63Β°F | 47Β°F | 24% less BTU |
| Panhandle | 60Β°F | 50Β°F | 20% less BTU |
| Northern US | 40Β°F | 70Β°F | Baseline |
Why tankless units are vulnerable: The heat exchanger in a tankless unit has narrow channels (some under 1/16" wide) that concentrate mineral deposits. Unlike a tank water heater where scale sinks to the bottom, in tankless units it coats the heat exchanger directly β the highest-heat area. At 15+ GPG, visible scale can build within 6β12 months.
Scale protection options (FL-specific):
β’ Annual descaling flush (minimum): $125β$250/year service call. White vinegar or citric acid flush circulated through the heat exchanger. Required in most FL counties to maintain warranty.
β’ Polyphosphate scale inhibitor filter: $75β$200 installed, $40β$80 cartridge every 6 months. Low cost, reduces (doesn't eliminate) scale. Good for moderate hardness (<14 GPG).
β’ Electronic/magnetic scale inhibitor: $200β$500 installed. No salt, no waste water. Effective for hardness under 16 GPG. Reduces crystal size but doesn't eliminate minerals.
β’ Water softener (best protection): $800β$2,500 installed. Eliminates scale entirely via ion exchange. Required by Navien, Noritz, and some Rinnai models to maintain warranty in FL. See our Water Softener Sizing tool for FL-specific sizing.
| FL County | Hardness | Scale Risk | Recommendation |
|---|---|---|---|
| Collier | 22 GPG | Extreme | Softener required |
| Lee | 20 GPG | Extreme | Softener required |
| Miami-Dade | 19 GPG | Very High | Softener required |
| Broward | 17 GPG | Very High | Softener required |
| Palm Beach | 15 GPG | High | Softener recommended |
| Sarasota | 14 GPG | High | Softener recommended |
| Hillsborough | 13 GPG | High | Scale inhibitor minimum |
| Orange / Orlando | 8 GPG | Moderate | Annual descale |
| Brevard | 10 GPG | Moderate | Scale inhibitor or descale |
| Duval | 6 GPG | Low | Annual descale only |
| Factor | Gas Tankless | Electric Tankless |
|---|---|---|
| Unit cost | $600β$1,800 | $250β$700 |
| FL install cost | $800β$2,200 | $400β$1,200 |
| FL annual energy cost | ~$220β$350/yr | ~$400β$650/yr |
| Max flow rate | 4β11 GPM | 2β4 GPM |
| Hurricane outage | Works (battery pilot) | No hot water |
| Scale sensitivity | Moderate | Higher (element coils) |
| Lifespan | 20β25 years | 10β15 years |
| Best for | Whole-house | Point-of-use / supplement |
| Item | Low | High |
|---|---|---|
| Gas tankless unit (condensing) | $900 | $1,800 |
| Gas installation labor (FL) | $800 | $2,200 |
| Gas supply line upgrade | $400 | $1,500 |
| Electric tankless unit | $250 | $700 |
| Electric installation (FL) | $400 | $1,200 |
| Panel upgrade (if needed) | $1,200 | $3,500 |
| Water softener (recommended FL) | $800 | $2,500 |
| Scale inhibitor filter | $150 | $400 |
| FL permit (typical) | $75 | $350 |
| Annual descaling service | $125 | $250 |
Built for Florida homes - accounting for Florida's hard water, hurricane-season demands, and county permitting.
Serving Palm Beach County & Florida - get matched with a licensed plumber
On this page, Florida tankless sizing estimates run about $800-$2,500, depending on home size, materials, and project scope. Use the calculator above for a Florida-specific estimate.
Pricing depends on the size and layout of your home, the pipe materials and fixtures you choose, your Florida region and local labor rates, and permit fees. Work that is more complex or harder to access generally costs more.
In Florida, minor maintenance may be DIY, but anything beyond that generally calls for a licensed plumber, and many jobs require a permit and inspection. When a permit, gas work, or your main water or drain lines are involved, hire a Florida-licensed plumber.
It depends on the cause and your specific policy. Sudden, accidental damage is more often covered than gradual wear-and-tear or maintenance - confirm the details with your insurer.
Many common jobs are completed the same day, while larger projects can take longer. Your licensed plumber can confirm a timeline after assessing your home.
Planning estimate, not a quote — confirm with a licensed Florida plumber. Confidence is qualitative: ranges reflect this page’s Florida assumptions, not a guaranteed price.
Estimates on this page are Florida-specific and reflect Tankless Sizing for typical Florida homes.
From this page: On this page, Florida tankless sizing estimates run about $800-$2,500, depending on home size, materials, and project scope. Use the calculator above for a Florida-specific estimate.
Your actual cost depends on your home's condition, layout, and local labor and permit rates.
From this page: Pricing depends on the size and layout of your home, the pipe materials and fixtures you choose, your Florida region and local labor rates, and permit fees. Work that is more complex or harder to access generally costs more.
Generally raises cost: harder access, older homes, added permits and inspections, premium fixtures or materials, and emergency or after-hours work.
Generally lowers cost: easy access, bundling several items in one visit, standard fixtures, and off-peak scheduling.
Curated Florida tools and resources related to this page.
Last reviewed: July 1, 2026 (US Eastern)
Reviewed by the FL Plumbing Tools editorial team.
Sources: Florida plumbing cost research and Florida Building Code / local authority-having-jurisdiction (AHJ) permit references.
Florida reference: Estimates and guidance reflect Florida labor rates, permitting, hard water, humidity, and coastal conditions.
Updates: Reviewed periodically and updated as Florida codes, permit fees, and market rates change.