Natural Gas Hot Water Heaters: Tank and Tankless Options Compared

Nobody shops for a water heater on a good day. The usual trigger is a puddle around the base of the old tank, or a shower that goes cold while the dishwasher runs. Because the replacement is often needed fast, it helps to know the basics before the plumber arrives. Natural gas units heat water quickly and cost less to run than electric resistance models in most parts of the country, and they keep working during short power outages if the pilot or igniter does not depend on electricity.

This guide compares tank and tankless designs, explains how to size a unit for your household, and then reviews six well-known models and lines using only what their names state. As of 2026 the big decision is not brand but format: a storage tank is simpler and lower in upfront cost, while a tankless heater saves space and provides an endless supply at a higher installation complexity. Always confirm local code and venting requirements with a licensed installer.

Quick Picks

How to Choose

Size the tank or flow rate to your household

For tanks, a general rule is 30 to 40 gallons for one to two people, 40 to 50 gallons for three to four, and 50 to 75 gallons for larger families. Look at the first-hour rating on the yellow EnergyGuide label, which tells you how much hot water you actually get in a busy hour. For tankless, add up the flow of fixtures you run at the same time and choose a unit that meets that gallons-per-minute figure at your local winter incoming water temperature.

Compare efficiency using Uniform Energy Factor

The Uniform Energy Factor, or UEF, is the standard efficiency rating in the United States. Standard gas storage tanks usually land between 0.58 and 0.70, while condensing and tankless designs reach 0.80 or higher. A higher UEF lowers operating costs, but the benefit only pays back if you use a lot of hot water. A light-use household may never recover a premium.

Check venting and fit

Natural gas heaters need safe venting. Atmospheric tanks use a vertical flue, power vent models use PVC through a wall, and condensing units use plastic piping plus a condensate drain. A tankless unit replacing a tank may need a larger gas line, since it can demand far more input at once. Measure height, width, and clearance, because tall tanks can bump against low ceilings. Also confirm that the drain pan, shutoff valve, and expansion tank, where required by local code, will still fit once the new unit is in place.

Weigh warranty, safety features, and maintenance

Look for a tank warranty of at least six years on the tank and one year on parts. A flammable vapor ignition resistant design is now standard on most gas tanks. Tankless units need annual descaling in hard water areas, and tanks benefit from flushing sediment yearly. Choose a product that a local installer is comfortable servicing. Ask what the installer’s labor warranty covers, because a long parts warranty is of limited value if no one nearby will honor it.

Our Picks Reviewed

Rinnai RU199iN Natural Gas Tankless Water Heater

Rinnai is a major tankless specialist. The model name states an indoor natural gas tankless heater, a format that heats water on demand instead of storing it. It is designed for homes that want a continuous supply for multiple bathrooms. Back-to-back showers, a running dishwasher, and a laundry load at once are exactly the kind of overlap that a stored tank handles poorly and an on-demand unit handles well.

• Pro: A tankless design delivers hot water on demand and frees up the floor space a tank would occupy.
• Pro: Natural gas fuel keeps operating costs low in most areas compared with electric heating.
• Con: Installation tends to be more involved than a like-for-like tank swap, particularly when gas lines or venting must be upgraded.

Who should skip it: owners on a tight upfront budget, and homes where upgrading gas lines and vents is impractical. Hard water areas also need a plan for regular descaling.

Navien NPE-240A2 Natural Gas Tankless Water Heater

Navien focuses heavily on high-efficiency tankless designs. The NPE-240A2 name identifies a natural gas tankless unit, positioned for households that want strong efficiency and steady hot water. Homeowners planning to stay for many years tend to weigh these units more favorably, because lower running costs have time to offset the larger initial project.

• Pro: Tankless design eliminates standby heat loss from a stored tank.
• Pro: A brand centered on tankless units generally means plenty of installer familiarity.
• Con: Tankless systems cost more up front and may need electrical, venting, and condensate work.

Who should skip it: renters and small-budget replacements, and anyone who wants the lowest possible installation cost. Very low water use households may not recover the investment.

Rheem Performance Platinum 50 Gallon Natural Gas Water Heater

Rheem is one of the most common water heater brands in the country, and the Performance Platinum name indicates a higher tier in its tank lineup. The 50 gallon size is the typical choice for family homes. It is the sort of purchase made when an old tank fails and the household wants an equivalent upgrade with a minimum of plumbing changes.

• Pro: A 50 gallon storage tank suits a family of three to four with typical daily use.
• Pro: Storage tanks are simple, familiar, and straightforward to replace.
• Con: A tank wastes some heat while holding hot water, and eventually runs out during extended back-to-back showers.

Who should skip it: households with very large hot water demand, and homes where a 50 gallon tank will not fit the utility space. Shoppers who dislike storing and heating water all day should look at a tankless unit instead.

A. O. Smith Signature 100 50 Gallon Tall Natural Gas Water Heater

A. O. Smith is a leading water heater brand. This name tells you three things: a Signature 100 series model, a 50 gallon capacity, and a tall form factor. It is a typical like-for-like swap in many homes. Sticking with the same size and fuel as the unit being replaced is usually the fastest, least disruptive route for a plumber.

• Pro: A tall 50 gallon tank is a familiar footprint, simplifying replacement of an older unit of the same type.
• Pro: A major manufacturer typically has wide parts and installer support.
• Con: Tall tanks need ceiling clearance, which can be tight in basements and closets.

Who should skip it: small closets with limited height, and homeowners who prefer continuous hot water without a stored tank.

Bradford White Defender Safety System Natural Gas Water Heater

Bradford White is frequently associated with professional plumbers, and the Defender Safety System name highlights a safety-focused natural gas tank. It is the sort of model installers like to put in because of its safety emphasis. Anyone with a heater in an attached garage or utility room near stored paint and solvents has good reason to care about that detail.

• Pro: A safety-oriented design is reassuring where the heater sits near living areas or flammable materials.
• Pro: Professional-channel brands can be easy to service through a local plumber.
• Con: Some pro-channel models are sold through installers rather than big-box stores, which can limit shopping options.

Who should skip it: do-it-yourselfers who want to buy off a shelf, and shoppers who prioritize the lowest possible price.

Rheem Performance 40 Gallon Tall Natural Gas Water Heater

This Rheem tank is described by its 40 gallon capacity and tall form. It sits at the smaller end of the family tank range and is a common choice for compact households. Couples, small families, and townhomes with short plumbing runs are the usual buyers for this size.

• Pro: A 40 gallon tank suits one to three people and takes up less space than larger models.
• Pro: Smaller tanks heat up faster and use less energy to stay hot.
• Con: A 40 gallon tank can run out sooner during high-demand mornings, especially with teenagers or guests.

Who should skip it: larger families and homes with big soaking tubs, where a 40 gallon supply may run lukewarm halfway through a bath.

Which One Fits

• Large family, many bathrooms: a tankless Rinnai or Navien, with upgraded gas supply.
• Standard family of four: the Rheem 50 gallon or A. O. Smith 50 gallon tall tank.
• Small household or condo closet: the Rheem 40 gallon tall tank.
• Landlords and installers wanting a dependable swap: the Bradford White Defender.
• Homes that plan to stay long term and want lower bills: lean toward a high-efficiency or tankless unit.

If winter comfort is on your mind beyond hot water, the room heater guide covers supplemental warmth, and the outdoor motion sensor light piece is useful for lighting up a utility entrance.

Common Mistakes

1. Buying by capacity alone without checking the first-hour rating.
2. Skipping the venting plan, then discovering the new unit needs a different flue or PVC route.
3. Forgetting that a tankless swap may require a bigger gas line and electrical outlet.
4. Ignoring annual maintenance, which shortens life through sediment and scale.
5. Buying a tall tank without measuring ceiling clearance first.

FAQ

Is a tankless water heater better than a tank?

It depends. Tankless saves space and provides continuous hot water, while tanks cost less up front and are simpler to install.

How long does a natural gas water heater last?

Tanks often last 8 to 12 years and tankless units 15 to 20 years with maintenance.

Can I install a gas water heater myself?

Gas, venting, and permits make this a job for a licensed plumber in most places. Mistakes can be dangerous.

What size tank do I need for a family of four?

Typically 50 gallons, though check the first-hour rating and your peak usage patterns.

Does a gas water heater work in a power outage?

Many standing-pilot tanks do, but power vent and tankless models usually need electricity. Check the specific model’s requirements.