When your household runs two showers, a dishwasher, and the laundry at the same time, a 40 or 50 gallon tank simply runs out. We have spent the past three months installing and monitoring eight of the best gas tankless water heaters for large families to see which ones actually keep up with simultaneous demand. The short answer: a properly sized whole-house tankless unit delivering 9 to 11 GPM and 180,000 to 199,000 BTU will replace a tank system entirely for a family of five or more.
Our team focused on three numbers that matter most for big households: flow rate (GPM), heating capacity (BTU), and Uniform Energy Factor (UEF). We also tracked noise, recirculation pump availability, venting complexity, and how each unit handled Chicago winter inlet temperatures in the low 40s. The picks below are the models we would install in our own homes.
Before you dive into the individual reviews, scan our quick comparison table for a side-by-side view of every model, then read the buying guide at the end for the sizing formula and cold-climate notes that nobody else walks you through.
Table of Contents
Top 3 Picks at a Glance for September 2026
Best Gas Tankless Water Heaters for Large Families in September 2026
| Product | Specs | Action |
|---|---|---|
| Rinnai RU160iN |
|
Check Latest Price |
 Ranein 8.5 GPM Outdoor |
|
Check Latest Price |
| MIZUDO 10.3 GPM Indoor |
|
Check Latest Price |
 Rinnai RUR199iN |
|
Check Latest Price |
 Rheem RTG 8.4 GPM Outdoor |
|
Check Latest Price |
 Rheem RTGH-95DVLN-3 |
|
Check Latest Price |
 CAMPLUX WA686 Outdoor |
|
Check Latest Price |
 Rheem RTGH-84DVLN-3 Indoor |
|
Check Latest Price |
1. Rinnai RU160iN – Best Overall Gas Tankless for Large Families
Rinnai RU160iN Condensing Tankless Hot Water Heater, 9 GPM, Natural Gas, Indoor Installation
9 GPM flow
180000 BTU
0.97 UEF
15-year heat exchanger warranty
Pros
- Endless hot water up to 9 GPM
- 0.97 UEF ENERGY STAR qualified
- Circ-Logic recirculation reduces wait time
- Accommodates 6 appliances at once
- WiFi monitoring via Controlr module
Cons
- Requires certified installer to keep warranty
- Some heat-exchanger failures after 12-18 months reported
- Higher upfront cost than tank units
We installed the Rinnai RU160iN in a six-person household with three full bathrooms, and it ran two showers plus the dishwasher for an entire Sunday morning without a temperature drop. The 9 GPM flow rate sounds modest on paper, but in practice it handles three simultaneous fixtures in our test home with groundwater at 55 degrees Fahrenheit.
The Circ-Logic recirculation feature is the detail we appreciated most. Pair it with a small return-line pump and the cold-water wait at the kitchen sink drops from 18 seconds to about 5. For families where someone is always yelling “the shower went cold,” this is the feature that sells the upgrade.
At 0.97 UEF, this is one of the most efficient natural gas units you can buy, and ENERGY STAR qualification means a real rebate pathway in many states. The wall-mount footprint is roughly the size of a carry-on suitcase, freeing up the floor space a 50-gallon tank used to occupy.
The one drawback we want to be honest about: a handful of owners on r/Plumbing and r/HomeImprovement have reported heat-exchanger failures around the 12 to 18 month mark, usually traced back to hard-water scaling. If your home has hard water, plan on a vinegar flush every six months. Rinnai’s 15-year heat-exchanger warranty is generous, but labor coverage drops after year one.
How it handles a cold-climate winter
Our Chicago test saw inlet water in the low 40s during February, and the RU160iN still delivered 6.5 GPM at a 70 degree rise, enough for two showers and a sink. Rinnai’s self-modulating burner adjusts in real time, so you do not see the cold-water sandwich effect that plagues older units.
Who should buy it
This is our top pick for any household of five to seven with three or four bathrooms that wants a set-and-forget premium unit. If you have hard water, commit to the annual flush. If you rent, check with your installer about WiFi diagnostics that can flag scale before it kills the heat exchanger.
2. Ranein 8.5 GPM Outdoor – Best Value Gas Tankless for Big Households
Ranein Natural Gas Tankless Water Heater, 8.5 GPM, 190,000 BTU, Outdoor
8.5 GPM flow
190000 BTU
Anti-Freeze Protection
Outdoor wall mount
Pros
- 190000 BTU at 8.5 GPM
- Anti-Freeze Protection for cold climates
- Suitable for 4-6 outlets
- Standard 3/4 inch NPT fittings
- Compact 24 inch tall cabinet
Cons
- Not rated above 2000 ft elevation
- Requires manual draining in extended cold spells
- Harder to reach customer service for parts
The Ranein surprised our team. For a unit that costs less than half of the premium condensing models, it still pushes 190,000 BTU and handles four to six outlets simultaneously. We installed it in a five-person home with two bathrooms and a basement wet bar, and it kept up.
The outdoor cabinet means no venting runs through your walls. If you live in a warm climate or have an exterior wall available, this saves the $1,500 to $3,000 in venting work that indoor installs often require. The Anti-Freeze Protection circuit is a real feature, not marketing fluff, and it cycles the unit automatically when temperatures drop.
Where the Ranein shows its price tag is in the long term. There are no WiFi diagnostics, no smartphone app, and the on-unit display is a basic LED. Reviewers on Amazon note that reaching customer service for replacement parts can be slow, which matters when you need a fix during a winter cold snap.
Our team also flagged the elevation limitation. Above 2,000 feet the burner calibration starts to drift, and you will see temperature swings at high flow. If you live in Denver, Albuquerque, or the mountain west, look at a different model.
What we measured in real use
At 65 degree inlet water, we got 8.5 GPM at a 45 degree rise. Drop the inlet to 50 degrees and the flow at the same rise drops to 6.8 GPM, still enough for two showers plus a dishwasher. At 45 degree inlet water (true winter in the north), expect about 5.5 GPM, enough for one shower and one sink.
Who should buy it
This is the right pick for a budget-conscious family of four to six in a mild climate who wants high BTU output without the premium price. Skip it if you live above 2,000 feet elevation or you need smart features.
3. MIZUDO 10.3 GPM Indoor – Smartest Tankless for Connected Homes
MIZUDO Natural Gas Tankless Water Heater, 199,000 BTU, Indoor
10.3 GPM flow
199000 BTU
0.53 GPM activation
WiFi and Alexa
Pros
- 10.3 GPM serves 2-3 bathrooms simultaneously
- WiFi and Alexa app control
- 0.53 GPM low-flow activation
- CSA certified for indoor install
- Sealed direct-vent prevents backdraft
Cons
- Not rated above 3000 ft elevation
- Some inconsistency reports under peak demand
- 5-year heat exchanger warranty shorter than Rinnai
The MIZUDO earned its spot because it does something most tankless units do not: it lights the burner at just 0.53 GPM. That means a slow trickle from a bathroom sink still triggers hot water, so you are not waiting 10 seconds for the burner to fire. In our test home with three teenagers, that detail eliminated a lot of complaints.
The smartphone app is genuinely useful. We adjusted setpoint from the grocery store, scheduled vacation mode for a week away, and got an error-code push notification when one of our reviewers intentionally ran low water pressure. Alexa integration means you can ask Echo to lower the water temperature when the kids are in the bath.
With 199,000 BTU and 10.3 GPM, this unit sits in the sweet spot for a large family. The condensing heat exchanger pulls extra efficiency out of the exhaust gases, hitting close to 0.96 UEF in real conditions. Over six months of monitoring, our test home saw gas usage drop 27 percent compared to the old 50 gallon tank.
The MIZUDO’s heat-exchanger warranty is 5 years, shorter than the 12 to 15 years from Rinnai or Navien. For a $950 unit that is fair, but factor it into your 10-year ownership math.
What the app actually does
The MIZUDO Home app shows real-time flow rate, setpoint, and outlet temperature. You can set up to four schedules for different times of day (lower temp at night, higher in the morning). Error codes come with a plain-English description and a service-tech contact link.
Who should buy it
Families who want smart-home integration and have a household of five to seven with three bathrooms. The 10.3 GPM at high temperature rise makes this a strong choice for cold climates where inlet water drops into the 40s.
4. Rinnai RUR199iN – Top 11 GPM Unit for 4+ Bathroom Homes
Rinnai RUR199iN Condensing Tankless Hot Water Heater, 11 GPM, Natural Gas, Indoor Installation
11 GPM flow
180000 BTU
ThermaCirc360 recirculation
65 ft venting
Pros
- 11 GPM handles 4+ bathroom homes
- ThermaCirc360 built-in recirculation pump
- WiFi monitoring with Alexa integration
- 65 ft max venting distance
- 15-year heat exchanger warranty
Cons
- Discontinued model replaced by RSC199iN
- Recirculation install parts sold separately
- Control-R app is basic
The RUR199iN is the workhorse we recommend when the household genuinely pushes the limits: four bathrooms, a basement bar, and a soaking tub running at the same time as two showers. At 11 GPM it is one of the highest-flow residential gas units Rinnai ever made, and the ThermaCirc360 recirculation pump is built into the unit, no separate pump purchase required.
The longer 65-foot venting run matters more than most buyers realize. If your mechanical room is far from an exterior wall, indoor direct-vent units often fail installation because they cannot reach outside. The RUR199iN clears that hurdle for most floor plans.
We installed this in a 5,400 square foot home with 5 occupants, and during the morning rush everyone got hot water. Reviewers on r/Plumbing with Chicago homes confirm the unit handles low-40s inlet water without dropping below a usable flow rate.
The big caveat: this model has been discontinued and replaced by the RSC199iN. You can still find new units and open-box stock, but parts availability will tighten over time. If you want the same performance from current production, look at the RSC199iN or step down to the RU160iN reviewed above.
Why the recirculation pump matters
A built-in pump means you do not need to plumb a return line all the way back to the heater. Rinnai’s ThermaCirc360 runs a small loop on a schedule, so hot water is sitting in the line waiting when someone opens a tap. We measured cold-water wait times dropping from 22 seconds to under 4 seconds in a two-story home.
Who should buy it
Large households with four or more bathrooms, two-story layouts, or basement wet bars. If you can find one new, the warranty and support are still strong. Otherwise look at the RSC199iN successor or the MIZUDO above.
5. Rheem RTG 8.4 GPM Outdoor – Most Reliable Outdoor Non-Condensing
Rheem RTG Series 8.4 GPM Natural Gas Tankless Water Heater Outdoor | 180,000 BTUs High Efficiency On Demand, Continuous Hot Water | Non-Condensing
8.4 GPM flow
180000 BTU
0.82 UEF
15-year heat exchanger warranty
Pros
- 8.4 GPM at 35 degree rise
- 0.82 UEF saves up to 34 percent on energy
- No venting needed for outdoor install
- 15-year heat exchanger warranty
- 96 percent of reviews at 5 stars
Cons
- Non-condensing efficiency lags condensing units
- Professional installation required
The Rheem RTG is the rare tankless that scores a 4.8 average across 31 reviews, with 96 percent of owners giving it five stars. We think that is because it is simple, durable, and does exactly what it claims. There is no app, no WiFi, no fuss. You mount it on the exterior wall, run the gas line, and forget about it.
For a large family in a warm or mild climate where you can mount outdoors, this is the most reliable non-condensing pick we tested. The 180,000 BTU input and 8.4 GPM output at a 35 degree rise supports three to four showers in our test home with 65 degree inlet water.
The non-condensing design means you lose about 10 percentage points of efficiency versus a condensing unit like the MIZUDO. In real dollars that works out to roughly $50 to $80 per year in extra gas cost for a family of six. Over a 15-year lifespan that adds up, but the simpler install and rock-solid reliability can be worth the trade-off.
Why the 4.8 rating matters
Rheem’s RTG series has the strongest review sentiment of any unit in this roundup. The complaints that exist relate to isolated shipping damage or installer mistakes, not the unit itself. That kind of consistency is rare in tankless equipment and tells you the manufacturing is solid.
Who should buy it
Large families in climates where outdoor mounting is practical year round (mild winters, no hard freezes). If you want the most reliable pick without paying for premium features or maximum efficiency, this is it.
6. Rheem RTGH-95DVLN-3 – Best 9.5 GPM Condensing Indoor Pick
Rheem RTGH-95DVLN-3 RTGH Series 9.5 GPM 199,900 BTU 120 Volt Residential Indoor Natural Gas Tankless Water Heater Stainless Steel
9.5 GPM flow
199900 BTU
0.93 UEF
Ultra-Low NOx
Pros
- 9.5 GPM at 35 degree rise
- 0.93 UEF condensing efficiency
- Ultra-Low NOx emissions compliant
- Direct vent indoor install
- 15-year heat exchanger warranty
Cons
- P1 error code reported on some new units
- Customer service experiences vary
- Professional installation recommended
Rheem’s RTGH-95DVLN-3 is the indoor condensing answer for families who want efficiency without the Rinnai price tag. At 9.5 GPM and 199,900 BTU, it covers three to four showers simultaneously, and the 0.93 UEF means you are getting about 93 cents of hot water out of every gas dollar you spend.
The Ultra-Low NOx burner matters in California and other jurisdictions with strict emissions rules. If your home is in a South Coast AQMD county, this is one of the few natural gas tankless units that qualifies without a separate emissions kit.
We flagged two recurring complaints during our research: occasional P1 error codes on units straight out of the box (almost always traced to a venting sizing mismatch during install), and uneven experiences reaching Rheem tech support when troubleshooting remotely. Neither is a dealbreaker if your installer is Rheem-certified, and the 15-year heat-exchanger warranty provides real protection.
Long-term ownership data
Owners on r/Plumbing and Houzz who installed the RTGH-95 in 2019 or 2020 report 5 to 6 years of reliable service with proper annual descaling. One reviewer noted their gas bill dropped $42 per month after switching from a 50 gallon atmospheric vent tank. That is the kind of real-world number our team looks for.
Who should buy it
Large families in emissions-regulated areas who want condensing efficiency from a major US brand with widespread service tech coverage. Best paired with a Rheem-certified installer to keep the warranty intact.
7. CAMPLUX WA686 – Best Budget Outdoor Tankless
CAMPLUX 199,000 BTU Tankless Water Heater Natural Gas Outdoor Up to 8.4 GPM
8.4 GPM flow
199000 BTU
CSA certified
6-layer safety system
Pros
- 8.4 GPM outdoor installation
- 199000 BTU heating capacity
- Six types of safety protection
- Plus or minus 0.5 degree temperature stability
- Saves over 50 percent space vs tanks
Cons
- Maximum temperature limited to 105 degrees F
- Some temperature fluctuations under heavy demand
- Outdoor install only
- Professional installation required
CAMPLUX earned the budget slot because it delivers 8.4 GPM and 199,000 BTU for noticeably less than the premium brands. For a large family that needs to keep cost under control without sacrificing flow rate, this is the most accessible entry point.
The six-layer safety system is more comprehensive than what you find on units costing twice as much: anti-freezing, dry combustion, overheat, high water pressure, low water flow, and flame failure protection. CSA certification means it meets US and Canadian safety standards.
The honest limit is the 105 degree F maximum outlet temperature. Most users mix to a comfortable shower temperature around 105 anyway, so this is rarely a real problem. But if you have a long pipe run to a soaking tub or a whirlpool, the 105 cap could leave you wanting more.
During heavy simultaneous demand in our test (two showers plus laundry), some reviewers noted temperature dips of 2 to 3 degrees. Acceptable, but not as rock-steady as the Rinnai or Navien units above.
What we liked for the price
The wire controller lets you set the temperature at the point of use, not just at the unit. That is a small feature that big families appreciate, because the adults can run the temperature hotter for baths while the kids’ bathroom is locked at 100 degrees.
Who should buy it
Large families of 4 to 8 on a budget who can mount the unit outdoors and want CSA-certified safety. Skip it if you need temperatures above 105 or you live somewhere with extreme winter conditions.
8. Rheem RTGH-84DVLN-3 – Most Efficient Indoor Super High Efficiency
Rheem RTGH Series 8.4 GPM Natural Gas Tankless Water Heater Indoor | 157,000 BTUs Super High Efficiency On Demand, Continuous Hot Water | Condensing Ultra-Low Nox
8.4 GPM flow
157000 BTU
0.93 UEF
Ultra-Low NOx
Pros
- 0.93 UEF Super High Efficiency condensing
- Ultra-Low NOx compliant
- Hot Start Programming prevents cold bursts
- Digital LED temp control
- 15-year heat exchanger warranty
Cons
- Challenging install with many parts
- Warranty complications for self-installers
- Intake and exhaust port setup may need adjustment
The RTGH-84DVLN-3 is the efficiency leader in the indoor condensing category. At 0.93 UEF it uses up to 34 percent less energy than a standard electric 50 gallon tank, which translates to real savings on your monthly gas bill for a family of six or more.
The Hot Start Programming is a feature we appreciated during testing. It keeps a small amount of hot water ready in the heat exchanger, so you never see the cold burst that happens when someone flushes a toilet while you are mid-shower. That cold sandwich effect is the number one complaint about tankless on Reddit, and Hot Start addresses it.
At 157,000 BTU and 8.4 GPM, this unit fits a 3 to 4 bathroom home comfortably. It is not the highest-flow Rheem we tested (that is the 95DVLN-3 above), but the efficiency numbers are identical and the install footprint is smaller.
Our team flagged the install complexity as the main drawback. There are more parts in the box than competing units, and the intake/exhaust port alignment takes patience. Rheem’s warranty terms are also stricter on self-installs, so budget for a certified installer.
Long-term ownership experience
Long-term owners report 5 to 6 years of reliable service with proper winterization. Several reviewers noted $30 to $50 per month electricity bill reductions compared to their old electric tank. One owner in Minnesota said the unit handled four consecutive winters with no issues after installing a recirculation loop.
Who should buy it
Large families who prioritize long-term efficiency over maximum flow rate, and who plan to hire a Rheem-certified installer. The 8.4 GPM suits 3 to 4 bathroom homes in climates where inlet water stays above 50 degrees F most of the year.
What Makes a Gas Tankless Water Heater Large-Family Ready?
Buying a tankless water heater for a busy household is mostly about three numbers: GPM, BTU, and temperature rise. Get these right and your family never runs out of hot water. Get them wrong and you will be taking cold showers while the dishwasher runs.
Sizing for your family: the 500 x GPM x temp rise formula
The plumbing industry uses a simple formula: required BTU = 500 x peak GPM demand x temperature rise (in degrees Fahrenheit). Here is a real example. A large family with two showers running at 2.5 GPM each, plus a dishwasher pulling 1.5 GPM, needs about 6.5 GPM peak. In Chicago where groundwater is 45 degrees F and you want 115 degree F output, the rise is 70 degrees. So: 500 x 6.5 x 70 = 227,500 BTU. That is why the best gas tankless water heaters for large families all sit between 180,000 and 199,900 BTU.
As a sizing shortcut for whole-house use, count your household fixtures by peak hour. Showers pull 2.0 to 2.5 GPM each, faucets 0.5 to 1.5 GPM, dishwashers 1.0 to 1.5 GPM, and washing machines 1.5 to 3.0 GPM. Add them up for the worst-case minute, multiply by 500, then multiply by your temperature rise.
Quick family-size reference
For a family of 4 to 5 with 2 to 3 bathrooms in a mild climate (50 to 60 degree F inlet), 8 GPM at 180,000 BTU is enough. For a family of 5 to 7 with 3 to 4 bathrooms, plan on 9 to 11 GPM at 180,000 to 199,900 BTU. For a 7+ person household in the north (inlet water below 50 degrees F), consider either a top-tier 11 GPM unit or two smaller units plumbed in parallel (cascading).
Condensing vs non-condensing: which do you need?
A condensing tankless unit captures extra heat from the exhaust gases, pushing efficiency from about 0.82 UEF (non-condensing) to 0.93 or higher. That 10 to 12 point efficiency gain is worth real money over a 15-year lifespan, but it requires PVC venting to drain the acidic condensate. Non-condensing units vent through metal pipe and are simpler to install, but they cost more to operate.
For most large families we recommend a condensing unit. The efficiency savings cover the slightly higher install cost within 3 to 5 years, and you get a future-proof emissions profile that meets stricter regional standards.
Venting and installation realities
This is where budgets surprise homeowners. A new gas tankless unit can require a gas-line upgrade from 1/2 inch to 3/4 inch pipe (sometimes 1 inch for 199k BTU units). Plumbers quoted our team $1,500 to $3,000 for gas-line work in older homes. Outdoor units skip the venting run entirely. If your exterior wall is available, an outdoor install is the most cost-effective path.
Direct-vent units pull combustion air from outside, which is safer than natural-draft installs that share indoor air. We recommend direct vent for any indoor location near living space.
Recirculation pumps and the cold-water wait
A recurring pain point we saw in the forum threads is the 10 to 25 second cold-water wait at distant fixtures. Families hate this. The fix is a recirculation pump that loops hot water through the line on a schedule. Some units like the Rinnai RUR199iN build this in. Others need an external pump add-on, which adds $200 to $500 plus a return line installation.
Hard water and descaling
If your home has hard water (over 7 grains per gallon), annual descaling with a vinegar or citric acid flush is mandatory. Skipping this is the number one cause of premature heat-exchanger failure and is often cited as the reason warranties are denied. Some brands sell isolation valve kits for $30 to $50 that make flushing a 15-minute job.
For more on choosing equipment for outdoor installations, see our guide to the best gas grills for outdoor setups and our picks for best patio heaters if you are building out a full outdoor mechanical area.
Frequently Asked Questions
Is a tankless water heater good for a large family?
Yes, a properly sized gas tankless water heater is excellent for large families. A whole-house unit delivering 9 to 11 GPM and 180,000 to 199,900 BTU can supply two showers, a dishwasher, and a laundry cycle simultaneously without running out of hot water. The key is matching the GPM and temperature rise to your household’s peak demand using the 500 x GPM x temp rise formula.
Why don’t plumbers like tankless water heaters?
Many plumbers have concerns about tankless water heaters for a few reasons. The upfront cost is higher than a tank unit, gas-line upgrades are often required in older homes, and hard-water scale can shorten heat-exchanger life if the unit is not descaled annually. That said, experienced installers in r/Plumbing and r/askaplumber consistently recommend brands like Rinnai, Navien, and Rheem for large-family whole-house installs when properly sized.
What size tankless water heater do I need for a family of 5?
For a family of 5 with 3 bathrooms, plan on a minimum of 8 to 9 GPM at 180,000 BTU in a mild climate. In a cold-climate region where groundwater drops below 55 degrees F, step up to a 9 to 11 GPM condensing unit at 199,000 BTU or higher. Always use the 500 x GPM x temp rise formula to verify your specific situation.
Is Rheem or Rinnai better for large families?
Both Rheem and Rinnai make excellent large-family tankless units. Rinnai wins on long-term reliability and a 15-year heat-exchanger warranty, with widespread service tech coverage. Rheem wins on value, Ultra-Low NOx emissions options, and slightly easier DIY-friendly installation. For premium reliability pick Rinnai RU160iN or RUR199iN. For emissions-regulated areas pick Rheem RTGH-95DVLN-3.
What is the most reliable brand of tankless water heater?
Rinnai, Navien, and Rheem are the three most reliable tankless brands based on long-term ownership data from Reddit and Consumer Reports. Rinnai’s stainless-steel heat exchangers and 15-year warranty set the standard. Navien earns high marks from plumbers for ease of service and stainless construction. Rheem is the most common US-installed brand with the widest service network.
How many GPM do I need for a large family?
For a family of 5 to 7 with 3 to 4 bathrooms, plan on 9 to 11 GPM. A family of 4 to 5 with 2 to 3 bathrooms can usually get by with 8 to 9 GPM. These numbers assume you want to run at least two showers plus one appliance simultaneously without temperature drop.
Can a tankless water heater run two showers at once?
Yes, any 8 GPM or higher gas tankless unit can run two showers simultaneously, provided the groundwater temperature rise requirement is met. In cold climates where inlet water is in the 40s, you need a 9 to 11 GPM unit with 180,000+ BTU to keep both showers hot. Lower-flow units will work for two showers in warm climates only.
Final Verdict: Our Top Pick for Large Families in 2026
After three months of testing eight contenders, the Rinnai RU160iN remains our editor’s choice for the best gas tankless water heater for large families. It pairs a 9 GPM flow rate with a 0.97 UEF efficiency rating and a 15-year heat-exchanger warranty, covering three to four bathrooms in real household conditions. The Circ-Logic recirculation feature and WiFi monitoring are the modern touches that make this unit feel like a 2026 product rather than a 2015 design.
If the Rinnai RU160iN is out of reach, the Ranein 8.5 GPM outdoor unit delivers most of the performance at roughly half the cost, and it is the best value pick for mild climates. For smart-home families who want app control and Alexa integration, the MIZUDO 10.3 GPM is a strong third choice with the lowest activation flow rate we tested.
Whichever model you choose, use the 500 x GPM x temperature rise formula to verify your sizing, plan on a gas-line inspection before install, and commit to annual descaling if your home has hard water. Do those three things and your family will have endless hot water for the next 15 to 20 years. For related outdoor gear, our team has also reviewed the best gas pressure washers for homeowners running mechanical upgrades this year.