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A Complete Homeowner’s Guide (From Dor-Mar)
If you’re tired of running out of hot water mid-shower or staring at a bulky tank taking up half your utility room, a tankless water heater might be exactly what your home needs. This guide covers everything from how these systems work to what they cost, how to size one correctly, and why proper installation matters more than most homeowners realize.
Quick Answer: Is a Tankless Water Heater Right for Your Home?
A tankless water heater – sometimes called an on demand hot water heater or instant hot water heater – heats water only when you turn on a faucet. Cold water flows through the unit, passes over a heat exchanger, and exits at your desired temperature. There is no storage tank keeping dozens of gallons hot around the clock. Tankless heaters provide hot water on demand without storage, which means an endless supply of hot water as long as the unit is properly sized for your household.
The three questions homeowners ask most often are straightforward. First, will you get endless hot water? Yes – within the unit’s flow rate limits. Second, what does it cost? In Central Ohio, professionally installed whole-house models typically run between $4,000 and $7,500 depending on the unit, venting, and any gas line or electrical upgrades. Third, will you save money? Tankless water heaters can save 24 to 34 percent on energy bills compared to a standard 40- to 50-gallon tank, according to DOE research.
Here’s a real example: a family in Gahanna, Ohio, replaced their 50-gallon gas tank water heater with a natural gas tankless unit rated for roughly 9 GPM. Before the switch, two back-to-back morning showers regularly drained their tank. After the install, they run multiple showers and the dishwasher simultaneously without a drop in comfort.
Who’s a great candidate?
- Homes with an existing natural gas or propane gas line
- Busy families needing hot water from multiple fixtures at once
- Homeowners looking for space savings in a tight utility area
Who might need upgrades first?
- Homes with smaller electrical panels considering an electric tankless water heater
- Properties with undersized gas piping or limited venting paths
- Households with extremely high simultaneous hot water demand
If you’re considering the switch, Dor-Mar Heating, Air Conditioning & Plumbing can size, install, and maintain tankless water heaters for homes across Central Ohio, backed by a long-standing reputation as a family-owned HVAC and plumbing company. Call 740-345-6639 or schedule online at dormarhvac.com.
How a Tankless Water Heater Works (Gas & Electric)
Understanding how tankless water heaters work helps you make a smarter buying decision. The process is simpler than most people expect.
- Cold water enters the unit from your home’s water supply.
- A flow sensor detects water flow and signals the system to activate.
- A gas burner ignites (gas models) or electric heating element banks energize (electric models).
- Water passes through the heat exchanger, where it absorbs heat rapidly.
- Hot water exits and travels to your fixtures – shower, sink, dishwasher.
- When you close the tap, the unit shuts off. No wasted energy heating water that sits idle.
A gas tankless water heater uses natural gas or propane and is rated by BTU input – whole-house gas models commonly range from 150,000 to 199,000 BTU/h. These units require proper venting and adequately sized gas connections. An electric tankless water heater uses high-amperage heating elements measured in kilowatts (typically 18–36 kW for whole-house units) and needs no venting, but may require significant electrical panel capacity.
This on demand process eliminates standby heat loss – the energy a traditional tank water heater wastes just keeping stored water hot. Many modern tankless units also include a digital display for temperature settings and diagnostics, and some offer Wi-Fi or smart controls for remote monitoring.
Tankless vs. Traditional Tank Water Heaters
Here’s how the two water heating system types compare on the metrics that matter most:
| Feature | Tankless Water Heater | Traditional Tank Water Heater |
|---|---|---|
| Hot water delivery | On demand, continuous | Limited to tank capacity |
| Energy savings | 24–34% less energy consumption | Higher standby losses |
| Lifespan | 15–20+ years | 10–15 years |
| Space | Wall-mounted, significantly less space | Floor-standing, 40–80 gallons |
| Upfront cost | Higher ($1,000–$3,000+ for unit alone) | Lower ($1,000–$2,000 installed) |
| Maintenance | Annual descaling recommended | Anode rod replacement, periodic draining |
| Key advantages of tankless: |
- Consistent hot water that doesn’t run out mid-shower
- Longer equipment life when properly maintained
- Reducing energy consumption by eliminating standby heating
- Compact design that frees up valuable floor space
Where tank water heaters still make sense:
- Lower upfront cost for both equipment and installation
- Simpler installation in homes already configured for tanks
- Less sensitivity to simultaneous flow rate limits
Consider a typical Columbus-area home with a 50-gallon gas tank (efficiency factor around 0.60). In winter, that tank loses heat overnight and takes time to recover after heavy use. Replace it with a 9 GPM natural gas tankless unit, and the household can supply hot water to two showers and a dishwasher running at the same time – no recovery wait needed.
Pros and Cons of Tankless Water Heaters for Homeowners
Use this checklist to prepare your questions before calling Dor-Mar for a consultation.
Pros:
- Endless hot water within flow rate limits – no more cold surprises
- Energy savings of 24–34% over standard tanks, reducing energy consumption over time
- Tankless models occupy less space than traditional heaters, ideal for condos, small utility rooms, and garages
- Reduced risk of catastrophic tank leaks and water damage
Cons:
- Higher upfront cost – equipment plus professional installation for venting, gas line upgrades, or electrical work
- Tankless models may struggle with high simultaneous hot water demand if the unit is undersized
- Power dependency – even gas units need electricity for controls and ignition, so they won’t function during outages
- Some homes need gas line upsizing or electrical panel upgrades before installation is possible
Installed prices nationally range from roughly $2,000 to $6,000+ depending on the fuel type, unit capacity, and site conditions. Dor-Mar provides free estimates to pinpoint costs specific to your Central Ohio home.
Understanding Flow Rate: Will You Really Have “Endless” Hot Water?
A tankless water heater’s flow rate is measured in GPM (gallons per minute), and it’s the single most important number when determining whether a tankless unit can handle your household’s hot water needs.
Typical fixture flow rates:
- Shower: 2.5 to 3 GPM
- Bathtub faucet: 4 GPM
- Kitchen faucet: 1.5 GPM
- Clothes washer: 2–2.5 GPM
Here’s a practical example: a family in Westerville, Ohio, installs a unit with a maximum flow rate of 7.5 GPM – like the Stiebel Eltron Tempra 36 Plus, which delivers a maximum flow rate of 7.5 GPM. Running two showers (about 5 GPM total) and a dishwasher (about 2 GPM) simultaneously stays within that 7 GPM window. They get reliable hot water across all three fixtures.
Some higher-capacity models can deliver up to 10 GPM for multiple fixtures. The Rinnai RX180iN, for instance, has a maximum flow rate of 10 GPM, and the Takagi tankless water heater also provides a flow rate of 10 GPM, making either suitable for larger homes.
“Endless” hot water means the unit won’t run out of stored water the way a tank does. But tankless heaters can struggle to provide hot water during peak usage times if combined fixture demand exceeds the unit’s rated GPM. When hot water demand exceeds the unit’s capacity, the temperature can drop noticeably.
Temperature rise matters too. This is the difference between your incoming cold water temperature and the desired temperature at your tap. In Central Ohio winters, inlet water can be 40–45°F. Heating to 120°F means you need a 75–80°F rise. A higher temperature rise reduces how many GPM the unit can actually deliver, which is why climate plays a direct role in sizing.
Gas vs. Electric Tankless Water Heaters
Choosing the right tankless water heater depends heavily on your available fuel type, existing home infrastructure, and local utility rates.
Gas tankless water heater advantages:
Gas models – including both natural gas and propane – deliver higher flow rates, making them the go-to for whole house applications in colder climates like Central Ohio. A condensing gas unit can typically deliver 7–11 GPM at moderate temperature rise, handling multiple showers, sinks, and appliances simultaneously. Gas tankless heaters require proper venting (stainless steel for non-condensing, PVC or polypropylene for condensing) and gas connections sized for high BTU input.
Electric tankless water heater considerations:
Electric models shine as point-of-use solutions or in homes with milder climates where temperature rise is smaller. Tankless heaters have efficiency ratings up to 99% in electric configurations – the Rheem RTEX-13 offers a 99 percent efficiency rating, the Stiebel Eltron Tempra 36 Plus has a 99% efficiency rating, and the Rheem RTEX-36 delivers a 99.8% energy efficiency rating. However, electric tankless units for whole house use require substantial electrical service (often 150–200 amps or more), and many Central Ohio homes would need panel upgrades. Electric tankless heaters also tend to deliver lower GPM – the Rheem RTEX-36 can deliver up to 8.8 GPM under favorable conditions, but that drops in cold-inlet climates.
On operating costs, gas units are typically cheaper to run despite lower unit efficiency numbers. One analysis shows annual costs of roughly $2,150 for a condensing gas model versus approximately $6,900 for an equivalent electric unit at standard utility rates (source).
Dor-Mar’s licensed electricians and plumbers can evaluate whether your home’s panel and gas service are suitable for tankless, saving you from costly guesswork.
Condensing vs. Non-Condensing Tankless Units
Non condensing water heaters use a single heat exchanger. Exhaust gases exit at high temperatures, requiring more expensive vent materials like stainless steel. Non condensing units typically have a UEF (Uniform Energy Factor) of around 0.80–0.85 and cost less upfront.
Condensing units add a secondary heat exchanger that captures latent heat from exhaust gases before they vent. This results in cooler exhaust temperatures, allowing the use of less expensive PVC or polypropylene venting. Condensing units achieve UEF ratings of 0.90–0.97, translating to meaningfully lower energy costs over the unit’s life. The Rinnai RX180iN, a popular condensing gas model, carries an efficiency rating of 93–96%.
The trade-off is a modestly higher equipment cost and the need for condensate drainage (sometimes with a neutralizer kit). For 2024–2026 installations, condensing units have become the preferred solution where long-term energy savings and lower utility bills are priorities. Dor-Mar handles condensate routing as a standard part of every condensing installation.
When deciding between the two, weigh the higher upfront cost of a condensing model against years of reduced fuel bills. In most cases, the condensing unit pays for the difference within a few years.
Indoor vs. Outdoor Tankless Installation
Central Ohio: indoor installation is standard. Freezing winter temperatures make outdoor installation risky unless the unit has robust freeze protection and weather-rated enclosures. Most Central Ohio homes mount their tankless unit in a basement, garage, or utility room. Indoor considerations include vent location and routing, gas line access, condensate drain placement, and proximity to main hot water distribution lines to minimize wait time.
Dor-Mar is experienced with both indoor and outdoor installation approaches and can advise which makes sense based on your climate, home layout, and local building codes.
Key Features to Look For in the Best Tankless Water Heaters
Use this checklist when comparing models online, then bring your priorities to a Dor-Mar consultation for professional installation guidance.
Performance features:
- Adequate flow rate (GPM) for your household – a household with four or more people may need 8 to 9 GPM
- Condensing technology for higher energy efficiency and lower operating costs
- Wide modulation range for consistent hot water temperature across varying flow demands
- Strong energy efficiency ratings – look for Energy Star certification, which indicates high energy efficiency ratings, and a UEF of 0.90 or above for gas models
- Advanced flow control technology for stable water temperature during demand changes
Comfort and convenience features:
- Digital display for precise temperature control and error code readout
- Remote or Wi-Fi connectivity for monitoring and adjusting temperature settings from your phone
- Recirculation compatibility for instant hot water at distant fixtures
- Safety shutoff systems for overheating, exhaust blockage, or combustion issues
Maintenance-friendly features:
- Scale-detection programming and maintenance reminders
- Easy-access inlet filters for quick cleaning
- Compatibility with Dor-Mar’s annual maintenance visits
Bring a short list of “must have” features – like outdoor installation capability, a specific GPM requirement, or smart-home integration – to your Dor-Mar consultation so technicians can match you to the right tankless model.
How to Properly Size a Tankless Water Heater for Your Home
Sizing a tankless water heater isn’t about square footage or bedroom count. It comes down to two variables: peak hot water demand (total GPM from all fixtures running at once) and temperature rise (how much the unit needs to heat your incoming water).
Step 1: Calculate peak GPM. Add up the GPM of every fixture you might use simultaneously during your busiest time. Two showers (5–6 GPM) plus a washing machine (2–2.5 GPM) puts you at roughly 7–8.5 GPM.
Step 2: Determine temperature rise. In Central Ohio, winter inlet water is often 40–50°F. To reach 120°F, the unit needs a 70–80°F rise.
Step 3: Match BTU rating. Gas input must be sufficient for both the flow rate and the temperature rise. Heating water from 40°F to 120°F requires about 100,000 BTUs per hour – whole house gas models at 150,000–199,000 BTU/h can handle the higher demands of cold-climate homes. The BTU rating is essentially how much heating power the burner can produce; more BTU means more hot water at higher rises.
Whole-house models provide hot water to multiple fixtures simultaneously, but only when sized correctly. Dor-Mar technicians use real-world data, manufacturer sizing charts, and local climate knowledge to recommend properly sized equipment – avoiding both the frustration of undersizing and the waste of oversizing.
Real-World Benefits: Energy Savings, Comfort, and Space
Energy savings you can actually feel on your bills. When replacing an older, lower-efficiency tank with a high-efficiency tankless unit, homeowners typically see energy savings of 24–34%. That translates to meaningful reductions in energy bills year after year, with the tankless unit often paying back its higher upfront cost within 5–12 years depending on usage and fuel costs. The key to these savings: your tankless unit only fires when you actually need hot water, eliminating the wasted energy of keeping 40–80 gallons constantly heated.
Comfort that goes beyond “enough hot water.” No more scheduling showers around tank recovery time. Long showers, running the dishwasher while someone bathes, filling a soaking tub – it all works within the unit’s rated GPM. Water temperature stays consistent thanks to modulating burners or elements that adjust output in real time.
Space savings that surprise homeowners. A wall-mounted tankless unit takes up significantly less space than a floor-standing tank. One Dor-Mar customer in Newark, Ohio, gained a full storage closet after replacing a bulky 50-gallon tank with a compact wall-mounted natural gas tankless water heater – a change that mattered in their smaller ranch home.
There’s an environmental angle too: reduced fuel consumption over the unit’s 20-year lifespan and fewer tank replacements headed to landfills contribute to lower overall resource use. How much energy you save depends on your specific setup, but the direction is consistently positive.
Installation: What to Expect from a Professional Dor-Mar Tankless Install
Here’s the typical process when Dor-Mar handles your water heater installation:
- In-home assessment. A technician evaluates your current water heating system, measures your household’s hot water demand, inspects gas/electric capacity, and reviews venting options.
- System selection. Based on the assessment, Dor-Mar recommends the appropriate fuel type, capacity, and tankless model for your home.
- Site preparation. This may include upgrading your gas line, adjusting venting, running condensate drains, or upgrading electrical panels – especially in older Central Ohio homes.
- Old unit removal. Your existing tank is disconnected, drained, and hauled away.
- Installation and commissioning. The new tankless unit is mounted, connected, and tested. Dor-Mar performs gas leak tests, verifies proper vent termination, checks condensate routing, confirms electrical safety, and validates correct flow rates and outlet temperatures.
Installation of tankless units typically costs more than traditional heaters due to the added complexity of venting, gas connections, and potential infrastructure upgrades. Professional installation is usually required to maintain manufacturer warranties and ensure code compliance – DIY installation for whole-house gas models is strongly discouraged.
Dor-Mar offers free or low-cost estimates and provides clear written proposals before any work begins, so there are no surprises on installation day.
Maintenance and Longevity of Tankless Water Heaters
Tankless water heaters typically last 20 years or more when properly installed and maintained, compared with 10–15 years for many standard tanks. That extended lifespan is one of the strongest arguments for the higher upfront cost – but it depends on consistent maintenance.
Key maintenance tasks:
- Flush tankless water heaters annually with vinegar to dissolve mineral scale (use a 5-gallon bucket and a small pump to circulate the solution through the unit)
- Clean inlet water filters to maintain proper water flow
- Inspect venting systems for gas models regularly to ensure safe exhaust gas discharge
- Verify combustion settings and burner operation on gas units
Maintenance is important for tankless systems to prevent mineral buildup, and this is especially true in Central Ohio, where hard water is common in many neighborhoods. Scale accumulation on the heat exchanger reduces efficiency and can shorten equipment life. Dor-Mar can also recommend water treatment solutions to help manage hardness before it reaches your unit.
Professional servicing is recommended once or twice a year. Dor-Mar’s Home Comfort Membership can include regular water heater checks, priority service, and discounts on repairs – a smart way to protect your investment and complement our HVAC maintenance packages.
Neglecting maintenance leads to error codes, reduced flow, temperature fluctuations, and a shortened equipment life that erases the longevity advantage tankless systems are known for.
Dealing with Scale Build-Up and Error Codes
Minerals in hard water – primarily calcium and magnesium – form scale on the heat exchanger over time. This coating reduces heat transfer efficiency, restricts water flow, and can eventually trigger error codes or cause the unit to shut down entirely. Check for scale build-up to prevent malfunctions before they become expensive repairs.
Warning signs to watch for:
- Fluctuating water temperature during use
- Noticeably reduced flow rate from hot water fixtures
- Error messages appearing on the digital display
- Unusual rumbling or clicking noises from the unit
While some minor cleaning (like rinsing inlet filters) can be handled by a handy homeowner, most descaling and troubleshooting for gas tankless systems should be performed by a licensed professional for safety reasons. A proper descaling flush involves circulating a vinegar solution through the heat exchanger using a small submersible pump and a 5-gallon bucket – a straightforward procedure for a trained technician.
Dor-Mar technicians service many popular brands and can interpret brand-specific error codes, quickly isolating issues with sensors, ignition systems, or flow detection, a level of professionalism reflected in our customer reviews and testimonials. If you see recurring error codes, call for service rather than ignoring them – delayed attention can lead to costly heat exchanger damage.
Costs: Purchase, Installation, and Operating Expenses
Let’s break down what you’ll actually spend.
Equipment costs (unit only):
- Gas whole-house tankless (condensing): $1,200–$2,500
- Gas whole-house tankless (non-condensing): $1,000–$2,000
- Electric whole-house tankless: $300–$900
- Tankless heaters cost $1,000 to $3,000 before installation for most quality whole-house units
Installation costs (Central Ohio, 2026):
- Basic whole-house gas install: $4,000–$5,000
- Premium condensing install with full upgrades: $5,500–$7,500+
- Traditional tank models, by comparison, cost $1,000 to $2,000 installed
Higher upfront costs are associated with purchasing and installing tankless systems, but the math changes when you factor in longevity and energy savings. Installation of tankless units typically costs more due to venting, gas line work, permits, and sometimes electrical upgrades.
Long-term operating savings:
A Central Ohio home switching from a standard gas tank (EF ~0.60) to a condensing gas tankless (UEF ~0.95) can expect to reduce utility bills on water heating by roughly 25–34% annually. Over a 15- to 20-year life, those savings often total several thousand dollars – more than offsetting the higher upfront cost.
Small point-of-use electric units for single sinks or remote bathrooms cost far less ($100–$400 plus installation) and can solve specific hot water delivery problems without a whole-house overhaul.
Dor-Mar offers financing options where available, plus transparent quotes so you can budget confidently. Our Columbus HVAC and plumbing services team can help you evaluate tankless options locally. Request a free estimate to see exact pricing for your situation.
Special Applications: Bathrooms, Additions, and Vacation Homes
Tankless water heaters aren’t just for whole-house replacement. They solve specific problems in specific spaces.
- Bathroom remodels and additions: A compact point-of-use electric water heater installed under a vanity provides instant hot water to a distant powder room or basement bathroom without running long pipe from the main heater.
- Vacation homes and condos: Vacation homes benefit from tankless units that sit idle without wasting energy, then deliver hot water immediately when occupants arrive. The space savings matter in smaller condos and tight Central Ohio homes served by our Westerville HVAC and plumbing team.
- In-law suites and rental spaces: A dedicated tankless unit gives a separate living space independent hot water without overloading the main home’s system.
- Spa tubs and specialty fixtures: A booster heater sized for high-flow fixtures keeps the main system from being overtaxed.
Dor-Mar can design hybrid systems – pairing a main whole-house gas tankless with smaller electric point-of-use units for problem locations, an approach frequently used by our Westerville heating and plumbing experts. If you’re planning any renovation or addition, talk with Dor-Mar’s plumbing team early in the process to size and locate future tankless units correctly.
Dor-Mar’s Recommendations for Choosing the Right Tankless Water Heater
Since 1962, Dor-Mar has helped Central Ohio families make smart decisions about home comfort. Here’s how we approach tankless recommendations.
We prioritize reliability over price tags. The cheapest online model often lacks local parts availability, strong warranty support, and proven field performance. We recommend units with solid manufacturer backing, accessible parts, and a track record in our service areas.
Example homeowner profiles:
- Small Columbus condo (1 bath, 1–2 occupants): A compact electric tankless unit or small gas non-condensing model. Lower flow rate needs, minimal upgrades, budget-friendly.
- Four-bath Westerville home (family of 5): A condensing natural gas tankless model rated for 9–10 GPM, with BTU input of 150,000–199,000. Handles multiple showers, dishwasher, and laundry simultaneously.
- Cape Coral, FL, home (2 bath, outdoor mount): An outdoor-rated gas or electric unit taking advantage of warm inlet temperatures and simpler venting. Less power consumption needed for temperature rise.
- Detached in-law suite in Gahanna: A point-of-use electric unit paired with the main home’s whole-house gas tankless for a hybrid approach, similar to solutions our Worthington HVAC and plumbing specialists provide for multi-space properties.
Dor-Mar weighs fuel costs, flow rate needs, climate, home layout, and your budget when suggesting the best tankless water heaters for your situation, drawing on decades of experience as a leading Columbus heating and cooling contractor. We’re brand-flexible and focused on matching the system to your family’s comfort and safety requirements.
FAQs About Tankless Water Heaters
Will I save money every month? Most households see energy savings of 24–34% on water heating costs. The exact savings depend on your current system’s efficiency, your usage patterns, and local energy costs.
Can a tankless water heater run multiple showers at once? Yes, if the unit is sized correctly. A gas model rated for 8–10 GPM can handle multiple showers and additional fixtures simultaneously. Showers typically use 2.5 to 3 GPM of hot water, so two showers plus a dishwasher require roughly 7–8 GPM.
How long do tankless water heaters last? Tankless water heaters typically last 20 years or more with proper maintenance – nearly double the lifespan of many traditional tanks.
Do they work during power outages? No. Both gas and electric models require electricity for controls, sensors, and ignition. A backup power source (generator or battery) would be needed for hot water during outages.
How often should they be serviced? Professional servicing is recommended once or twice a year, with annual descaling especially important in hard-water areas like Central Ohio.
What about electrical requirements for electric models? Electric tankless units for whole-house use often require 150–200 amps of electrical service. Many Central Ohio homes need panel upgrades to support this power consumption, which adds to installation cost. This is a major consideration when choosing between gas and electric models.
Are there rebates or incentives available? Some federal, state, and utility rebate programs apply to high-efficiency tankless units, particularly those with Energy Star certification. Programs change frequently – Dor-Mar can help you identify current incentives during your consultation.
What are some of the best tankless water heaters on the market? Several models stand out. The Rinnai RX180iN has a maximum flow rate of 10 GPM with an efficiency rating of 93–96%. The Rheem RTEX-13 boasts a 99% efficiency rating for point-of-use applications. The Rheem RTEX-36 can deliver up to 8.8 GPM with a 99.8% energy efficiency rating. And the Takagi tankless water heater provides a flow rate of 10 GPM for demanding whole-house applications. Your Dor-Mar technician can help match the right model to your specific needs.
Have a question not listed here? Call Dor-Mar directly at 740-345-6639 or schedule a consultation online.
How Dor-Mar Can Help: Consultation, Installation, and Membership
Dor-Mar Heating, Air Conditioning & Plumbing has been helping homeowners with water heater installation, repair, and maintenance since 1962. Our licensed technicians handle everything from simple point-of-use installs to complex whole-house condensing gas systems as part of our comprehensive HVAC and plumbing products and services.
Here’s how a typical consultation works:
- We assess your existing water heater and measure your household’s hot water needs.
- We inspect your gas, electric, and venting infrastructure.
- We present options with clear written estimates – no hidden costs.
For emergency situations – like a water heater failure in a Central Ohio January – Dor-Mar offers priority service to restore your hot water as quickly as possible.
Our Home Comfort Membership helps protect your tankless investment through routine checks, priority scheduling, and discounts on repairs. It’s the simplest way to keep your system running at peak efficiency for its full 20-year potential.
Ready to find out if tankless is right for your home? Call Dor-Mar at 740-345-6639, or book online at dormarhvac.com. We serve homeowners across Central Ohio, and we’d love to help your family enjoy reliable hot water for years to come.
