The short version: Tankless water heaters heat water on demand instead of storing 50 gallons hot 24/7. They cost $3,895-$7,495 installed in Montgomery County, last 20+ years (double a tank), save a family of four about $95-$200 per year in energy, and come with up to $1,400 in stackable rebates. They're the right call for most homes with 3+ bathrooms and gas service. They're the wrong call for single occupants, short tenures, or all-electric homes. This guide covers every detail.
What a tankless water heater actually is
A tankless water heater — also called an "on-demand," "instantaneous," or "continuous flow" water heater — is a wall-mounted appliance that heats water only when you turn on a hot water tap. Unlike the 50-gallon storage tank in your basement, there's no water stored and no standby heat loss.
Physically, it's about the size of a large carry-on suitcase. It mounts on a wall, vents through an exterior pipe, and connects to your gas line, cold water supply, hot water distribution, and a 120V electrical outlet. A modern condensing tankless in Maryland is roughly 27 inches tall, 17 inches wide, and 10 inches deep.
How a tankless water heater works
Every time you open a hot water tap — shower, dishwasher, laundry — here's what happens inside the unit, in about two seconds:
- Flow sensor activates. A sensor inside the unit detects water flowing and wakes up the control board.
- Gas burner ignites. The gas valve opens and a burner lights — typically 150,000-199,000 BTU, roughly five times the burner on a gas range.
- Water passes through heat exchanger. Cold water runs through a stainless steel or copper coil directly over the flame. It exits hot.
- Temperature modulates. A sensor reads outlet water temperature continuously and adjusts the gas flame up or down to maintain your set point (typically 120°F).
- Condensing unit recaptures heat. If you have a condensing unit (we only install condensing), exhaust gases pass through a secondary heat exchanger that captures additional heat from the water vapor, lifting efficiency to 0.96 UEF.
- Tap closes, unit shuts down. Flow sensor reads zero, burner extinguishes, fan purges the combustion chamber, system returns to standby.
The entire cycle — from turning the tap to hot water flowing — takes about 5-10 seconds for a unit near the tap, or 30-45 seconds for a tap at the far end of the house without recirculation.
The four types of tankless water heaters
Not all tankless units are created equal. They divide along two axes: fuel source and heat recapture.
By fuel source
Gas tankless (natural gas or propane). Most common in Maryland. Fires hard and heats fast — a 199K BTU gas unit handles 3-bathroom simultaneous demand easily. Requires venting, gas line of adequate diameter, and a 120V outlet for controls. This is what we install for 95% of Montgomery County jobs.
Electric tankless. Smaller, cheaper, no venting required. Limitation: electric tankless is usually underpowered for family-sized hot water demand in Maryland. A whole-home electric tankless strong enough for a 3-bath home needs a 150-amp dedicated circuit — a panel upgrade most homes don't have. Better suited to point-of-use applications (single sink, cabin, apartment).
See our detailed gas vs. electric tankless comparison for the decision framework.
By heat recapture
Non-condensing tankless. Single heat exchanger. Exhaust leaves the unit around 300°F — a lot of wasted heat. Vents out through stainless steel pipe. Efficiency peaks at about 0.82 UEF. Cheaper upfront but no longer our recommendation.
Condensing tankless. Secondary heat exchanger captures heat from exhaust gases, cooling the exhaust enough to vent through ordinary PVC. Efficiency reaches 0.96 UEF. Slightly more expensive. Significantly more efficient. This is what we install.
The real benefits — not the marketing version
Every tankless manufacturer advertises the same bullet points. Here's what actually plays out in Montgomery County homes after install:
Endless hot water (properly sized)
This is the headline benefit and it's real — if you buy the right size. A properly sized tankless delivers hot water forever. Your fourth shower is as hot as your first. Teenage morning routines stop colliding. A long soak in the master bath doesn't end the household's hot water budget.
Caveat: undersized units deliver lukewarm showers and cold finishes. We size carefully because this is the #1 complaint online about tankless — almost always traceable to an undersized install.
20+ year lifespan
Properly maintained tankless units routinely run 20-25 years. Tank heaters last 10-15. Over a typical 20-year Montgomery County homeownership tenure, you'll replace a tank once while owning the same tankless the whole time. The math: one $2,200 tank + one $2,500 replacement in year 12 = $4,700 over 20 years. One $3,895 tankless (net of rebates: ~$2,745) = $2,745 over 20 years. The tankless is cheaper over tenure.
Energy savings
Washington Gas estimates family-of-four savings around $95/year vs. a standard gas storage tank. Energy Star's lab testing shows condensing tankless units 24-34% more efficient for households using 41 gallons of hot water per day (the Energy Star test condition). That's not a life-changing number — roughly $8/month — but it compounds over 20 years to $1,800+ saved.
Reclaimed floor space
A 50-gallon tank occupies 4 square feet of basement or utility room floor. A wall-mounted tankless occupies zero floor space. In a Silver Spring rambler or a Potomac garage utility closet, that corner matters.
No flood risk
When a tank dies, it usually leaks — sometimes catastrophically. 50 gallons of water in your finished basement is a $10,000 insurance claim. Tankless units can't flood (there's nothing to hold water). A small leak from a fitting is measured in drops per minute, not gallons.
Rebates
Up to $1,400 in stacked rebates for Montgomery County homeowners. Tank heaters get essentially none. See the rebates page for the full four-rebate stack.
Ready for a real quote?
Skip the research — our 30-second instant estimator tells you your tier, fixed price, and rebate total.
The honest drawbacks
We're a tankless-only company, and we're still going to tell you where tank heaters win. These are the real downsides:
Higher upfront cost
A tankless install runs $3,895-$7,495 in Montgomery County. A tank runs $1,800-$2,800. The $2,000-$4,000 upfront premium is real. You make it back over 10-15 years through energy savings and the avoided tank replacement.
No hot water during a power outage
Even gas tankless units need 120V power for the fan and control board. During a power outage, you lose hot water. Tank heaters keep your water hot for 2-3 days after power dies. If you're on a well with frequent outages, this matters.
Annual maintenance in hard water areas
Montgomery County water is moderately hard. Tankless heat exchangers scale up over time. Annual descaling (~$150-195 professionally, or DIY for ~$60) is recommended. Tanks require anode rod replacement every 3-5 years ($150-250) which most homeowners skip entirely.
Gas line or electrical upgrades sometimes needed
A 199K BTU tankless draws 5x the gas of a 40K BTU tank. Older Montgomery County homes (pre-1980) occasionally need gas line diameter upgrades ($495 on our menu). Newer homes rarely do.
Minimum flow threshold
Tankless units require a minimum flow (typically 0.5-0.75 GPM) to fire up. A dribbling bathroom faucet may not trigger heating. This is rarely an issue in practice but occasionally surprises people.
Cost: the full breakdown
Our fixed-price tiers in Montgomery County:
| Tier | Fixed Price | Net of Rebates | Best For |
|---|---|---|---|
| Essential | $3,895 | ~$2,745 | 2-3 bathroom homes |
| Signature | $5,295 | ~$4,145 | 3-4 bathroom homes, recirc included |
| Whole-Home Pro | $7,495 | ~$6,345 | 4+ bathroom estates |
Full cost breakdown — unit vs. labor vs. permits vs. rebates — is on our dedicated Maryland cost guide.
Financing
0% APR for 12 months available through Wisetack on balances up to $10,000 (no impact on credit score). Longer-term options through GreenSky at competitive fixed APRs. Typical 60-month payment on a Signature tier install: ~$95-130/month.
How to size a tankless water heater
Sizing is the single most important decision in your install. Undersized units = lukewarm showers. Here's the short version of our full sizing guide:
You need to calculate two numbers:
- Peak simultaneous GPM demand — sum of all fixtures likely to run at the same time. Shower = 2.5 GPM. Sink = 1.5 GPM. Dishwasher = 1.5 GPM. Laundry = 2.5 GPM.
- Temperature rise required — typically 75-80°F in Maryland winter (45°F incoming water to 120°F outgoing).
Most 3-bathroom Montgomery County homes need a 10+ GPM unit at that temperature rise, which maps to our Signature tier (Navien NPE-240A2 or Rinnai RX160iN).
Brands worth buying
We install three brands only. Skipping the rest isn't snobbery — it's experience with 200+ installs.
Navien — our most-installed brand
Built-in recirculation, best Wi-Fi, highest max GPM. Why it works for 55% of our installs.
See the breakdown →Rinnai — the reliability benchmark
Simplest to service, quietest operation, best for 15+ year ownership horizons.
See the breakdown →Rheem — the value pick
US parts network, slightly lower price, 12-year warranty. Good for budget-sensitive 2-3 bath homes.
See the breakdown →Best tankless water heater 2026
Our ranked recommendations by home size, budget, and use case — with real install data.
See rankings →Installation — what actually happens
We've documented the full install experience on our how it works page, but the short version:
- Day 0: Get your instant estimate online (30 seconds) or book a free consult.
- Days 1-2: In-home consult. 45 minutes, licensed master plumber. Locked-in quote at the visit.
- Days 3-9: We pull Montgomery County permit (5-7 business days). Equipment ordered.
- Day 10: Install day. 6-8 hours on site. Old tank out by noon, new unit commissioned by mid-afternoon, first hot shower by dinner.
- Days 11-15: County inspector visits, signs off. Install officially complete. Rebate checks arrive in following weeks.
Maintenance — what's actually required
Tankless units aren't maintenance-free, but they're less needy than tanks. The core annual task is descaling — running a vinegar or commercial solution through the heat exchanger to dissolve mineral buildup. In Montgomery County's moderately hard water, this matters.
- Annual flush: $150-195 professional, or ~$60 DIY with a pump kit. We include the first year in every install.
- Air filter check: Most units have a small filter that needs a quick vacuum every 6 months.
- Condensate trap: Check annually for blockage. Takes 30 seconds.
- Error code watch: Wi-Fi-enabled units notify you via app. Most error codes are simple resets.
Our verdict — is tankless right for you?
Pick tankless if: You have 3+ bathrooms OR 3+ occupants, you have natural gas service, you plan to stay in your home 5+ years, and you want to capture the Maryland rebates. This describes roughly 75% of Montgomery County homeowners we talk to.
Stick with a tank if: You're selling within 3 years (payback period too long), you live alone with minimal hot water use, or you don't have natural gas service (electric tankless rarely pencils out).
Consider a heat pump water heater if: You have electric-only service and basement space for the heat pump footprint. Pepco offers up to $1,600 in rebates for heat pump water heaters — often a better electric solution than electric tankless.
Next steps
If you're still weighing the decision:
- Use our instant estimator to see your specific tier and net price
- Read our honest tank vs. tankless comparison
- See the full Montgomery County rebate breakdown
- Browse local pricing by city
- Book a free 45-minute consult — no commitment, no deposit