Tankless water heaters offer endless hot water and energy savings, but they cost more upfront than traditional tanks. If you're considering a tankless system for your Mount Pleasant, Charleston, or Daniel Island home, here's what to expect for installation costs in 2025.
Quick Cost Summary
| Tankless Type | Equipment | Installation | Total Cost |
|---|---|---|---|
| Electric (Whole Home) | $500-$1,500 | $800-$1,500 | $1,300-$3,000 |
| Gas (Whole Home) | $1,000-$2,500 | $1,500-$2,500 | $2,500-$5,000 |
| Point-of-Use Electric | $150-$500 | $150-$400 | $300-$900 |
Prices reflect Charleston, SC metro area rates for 2025
Gas Tankless Water Heater Costs
Gas tankless water heaters are the most popular choice for whole-home installation in the Charleston area due to their high flow rates and efficiency.
Equipment Costs
| Brand | Model Tier | Flow Rate | Price |
|---|---|---|---|
| Rheem | Entry | 6-7 GPM | $800-$1,200 |
| Rheem | Mid-Range | 8-9 GPM | $1,200-$1,600 |
| Rinnai | Mid-Range | 7-9 GPM | $1,200-$1,800 |
| Rinnai | Premium | 9-11 GPM | $1,800-$2,200 |
| Navien | Premium | 9-11 GPM | $1,800-$2,500 |
| Noritz | Various | 6-11 GPM | $1,000-$2,000 |
Installation Costs
Gas tankless installation is more complex than tank installation:
Basic Installation (replacing existing tankless): $1,000-$1,500
- Direct replacement
- Existing gas line adequate
- Existing venting adequate
Standard Installation (converting from tank): $1,500-$2,500
- New venting installation
- Possible gas line upgrade
- Electrical for controls
- Mounting and connections
Complex Installation: $2,500-$4,000+
- New gas line run
- Exterior venting through roof or wall
- Electrical panel upgrade
- Remote installation location
- Multiple unit installation
Additional Cost Factors
Gas Line Upgrade: $300-$1,000 Many older Charleston homes have 1/2" gas lines that are inadequate for tankless. Upgrading to 3/4" line is common.
Venting: $300-$800 Tankless units require stainless steel venting (Category III or IV). Most use direct vent through an exterior wall.
Condensate Drain: $100-$300 High-efficiency condensing units produce condensate that must be drained.
Permits: $50-$150 Required in Charleston County for gas appliance installation.
Electric Tankless Water Heater Costs
Electric tankless is simpler to install but requires significant electrical capacity.
Equipment Costs
| Type | Flow Rate | Price |
|---|---|---|
| Point-of-Use (single fixture) | 0.5-2 GPM | $150-$400 |
| Whole Home (small) | 3-4 GPM | $400-$700 |
| Whole Home (medium) | 4-6 GPM | $600-$1,000 |
| Whole Home (large) | 6-8 GPM | $900-$1,500 |
Installation Costs
Point-of-Use: $150-$400 Simple installation at a single fixture. Often DIY-able for handy homeowners.
Whole Home (adequate electrical): $800-$1,200
- Mounting and plumbing connections
- Electrical connections
- Testing and adjustment
Whole Home (panel upgrade needed): $2,000-$4,000
- Electrical panel upgrade: $1,000-$2,500
- New circuit installation
- Mounting and plumbing
Electrical Requirements
Whole-home electric tankless units require substantial power:
| Flow Rate | Power Required | Circuit |
|---|---|---|
| 4 GPM | 16-18 kW | 2-3 x 40A circuits |
| 6 GPM | 24-27 kW | 3-4 x 40A circuits |
| 8 GPM | 32-36 kW | 4 x 40A circuits |
Many Charleston area homes, especially older properties in downtown Charleston and established Mount Pleasant neighborhoods, require panel upgrades to support whole-home electric tankless.
Brand Comparison
Navien
Price Range: $1,800-$2,500 Best For: Premium efficiency, large homes Pros:
- Industry-leading efficiency (up to 0.97 UEF)
- Built-in recirculation pump option
- Excellent warranty
- Quiet operation
Cons: Higher price point
Rinnai
Price Range: $1,200-$2,200 Best For: Reliability, wide range of options Pros:
- Proven Japanese engineering
- Wide dealer network
- Multiple size options
- Good warranty
Cons: Some models louder than competitors
Rheem
Price Range: $800-$1,600 Best For: Value, availability Pros:
- Lower price point
- Widely available
- Good warranty
- Solid performance
Cons: Fewer high-end features
Noritz
Price Range: $1,000-$2,000 Best For: Commercial applications, reliability Pros:
- Japanese quality
- Good for high-demand applications
- Reliable performance
Cons: Smaller dealer network
Cost Comparison: Tankless vs. Tank
Is tankless worth the higher upfront cost? Here's a 15-year cost comparison:
| Factor | 50-Gal Gas Tank | Gas Tankless |
|---|---|---|
| Equipment + Install | $1,500 | $3,500 |
| Annual Operating Cost | $350 | $250 |
| Lifespan | 10-12 years | 20+ years |
| Replacement During Period | 1x ($1,200) | None |
| 15-Year Total Cost | $7,950 | $7,250 |
Tankless wins on long-term economics, plus provides unlimited hot water and saves space.
Installation Considerations for Charleston Homes
New Construction (Daniel Island, Park West)
New homes often include:
- Pre-run gas lines sized for tankless
- Electrical capacity for any system
- Ideal venting locations
- Lower installation complexity
Typical Cost: $2,500-$4,000 (gas tankless, installed)
Existing Homes (Established Mount Pleasant, Downtown Charleston)
Converting from tank to tankless may require:
- Gas line upgrades
- New venting runs
- Electrical work
- More complex installation
Typical Cost: $3,000-$5,000 (gas tankless, installed)
Coastal Properties (Sullivan's Island, Isle of Palms)
Special considerations:
- Salt air corrosion resistance
- Outdoor vs. indoor installation
- Hurricane strapping
- Limited natural gas (propane common)
Typical Cost: $3,500-$5,500 (gas tankless, installed)
Ways to Save on Tankless Installation
1. Utility Rebates
Check with Dominion Energy and local utilities for rebates on high-efficiency tankless water heaters. Rebates of $200-$500 are sometimes available.
2. Federal Tax Credits
High-efficiency water heaters may qualify for federal tax credits under the Inflation Reduction Act. Consult a tax professional.
3. Get Multiple Quotes
Prices vary significantly between contractors. Get 3+ quotes from licensed plumbers.
4. Consider Timing
Off-peak seasons (spring, fall) may offer better pricing and availability than emergency summer or winter replacements.
5. Bundle Work
If you need other plumbing work, bundling with tankless installation may reduce overall costs.
Choosing the Right Size
Proper sizing is critical for tankless satisfaction:
Flow Rate Calculation
Add up the flow rates of fixtures you'll use simultaneously:
- Shower: 2.0-2.5 GPM
- Bathroom faucet: 1.0-1.5 GPM
- Kitchen faucet: 1.5-2.0 GPM
- Dishwasher: 1.5 GPM
- Washing machine: 2.0 GPM
Example: 2 showers + 1 faucet = 5-6.5 GPM needed
Temperature Rise
Charleston's incoming water temperature is approximately 65-70°F. To reach 120°F output, you need 50-55°F temperature rise.
Sizing Rule: Higher temperature rise = lower flow rate capacity
A unit rated for 9 GPM at 35°F rise may only deliver 6 GPM at 50°F rise.
Service Areas
Water Heater Doctors installs tankless water heaters throughout the Charleston Lowcountry:
Mount Pleasant - All neighborhoods including Park West, Dunes West, I'On, and Belle Hall.
Daniel Island - Complete residential and commercial coverage.
Charleston - Downtown, West Ashley, James Island, Johns Island.
Sullivan's Island - Full service for island homeowners.
Isle of Palms - Including Wild Dunes.
FAQ: Tankless Installation Costs
How long does tankless installation take? Straightforward installations take 4-6 hours. Complex installations with gas line work or venting may take 1-2 days.
Is tankless cheaper to install than a tank water heater? No, tankless installation costs more upfront. However, lower operating costs and longer lifespan often result in lower lifetime costs.
Do I need to upgrade my gas line for tankless? Often yes. Many homes have 1/2" gas lines that are inadequate for tankless. Your installer will assess this.
Can I install tankless myself? Gas tankless requires licensed installation. Electric point-of-use units are sometimes DIY-friendly, but whole-home electric typically requires an electrician.
What brands do you recommend? Navien and Rinnai for premium applications, Rheem for value. We're factory-certified for all major brands.
Ready for a tankless water heater quote? Water Heater Doctors provides free estimates for tankless installation throughout Charleston, Mount Pleasant, Daniel Island, Sullivan's Island, and Isle of Palms. Call (843) 990-6524 to schedule your consultation.