The best 50 gallon gas water heater is not one machine, it is two. A standard atmospheric vent tank and a power vent tank both come in 50-gallon sizes, both burn natural gas, and a list that ranks them by brand name alone skips the one fact that actually decides the purchase: what your flue can handle and how many showers you run back to back.
No public failure database exists for any tank by brand or by model, the same gap I laid out in the piece on water heater brands, so a ranking that pretends to know which name lasts longest is guessing. What can be compared honestly is the vent type each one needs and the recovery rate each one delivers, both of which sit right on the spec sheet. This page works through a standard 40,000 BTU atmospheric model and a 50,000 BTU power vent model at the same 50-gallon size, prices both against the same household, and tells you which flue situation and which shower schedule each one actually fits.
The short answer
- An existing masonry or metal B-vent chimney with good draft, and the tightest budget: the standard atmospheric model. It is the cheaper of the two to buy and asks nothing extra of the house.
- No usable vertical flue, or the vent run has to go out a side wall: a power vent model, or a direct vent unit if the combustion air has to come from outside too.
- Two or three showers running back to back most mornings: the power vent’s 97-gallon first-hour rating beats the atmospheric model’s 84 by enough to matter.
- Chasing the lowest running cost at this tank size without going tankless: the power vent’s higher efficiency saves about $46 a year, real money but modest next to what a tankless unit can save.
- Already running out of hot water on busy mornings at 50 gallons: that is a sizing question, not a vent question, and first-hour rating versus recovery rate walks through it.
- No gas line reaches the house: stop here and read gas versus electric instead, because the fuel question comes before the vent question.
How a 50-gallon gas tank splits in two
An atmospheric model pulls the air it burns from the room around it and lets the exhaust rise on its own through a vertical flue, the same way a furnace did for decades. It needs no electricity and no blower, which is part of why it is usually the cheaper tank to buy. A power vent model burns the same gas but pushes its exhaust out with a small electric blower, through narrower pipe that can run horizontally to a side wall instead of straight up through a roof. That blower is also why the power vent model in this comparison carries a bigger burner, 50,000 BTU against 40,000, and a better Uniform Energy Factor, 0.72 against 0.62: forced draft pulls combustion air through the burner on its own schedule instead of relying on heat rising up a chimney, and less of that heat escapes unused.
I have laid out the full venting decision, including when a direct vent model belongs in the conversation instead of either of these two, in direct vent versus power vent. This page assumes you already know roughly which vent type your house can take, and compares what you actually get at 50 gallons once you do.
Side by side
| criteria | ATMOSPHERIC40,000 BTU, UEF 0.62 | POWER VENT50,000 BTU, UEF 0.72 |
|---|---|---|
| First-hour rating | 84 galpublished spec sheet | 97 galpublished spec sheet+13 gallons |
| Running cost per year | $330220 therms at $1.50 | $284189 therms at $1.50cheapest to run |
| Ten-year energy | $3,300site model | $2,840site model |
| Equipment price | $700 to $1,30050 gallon gas tank, either vent typetends toward the lower end | $700 to $1,300blower and vent kit push it toward the top |
| What the house needs | A usable vertical fluemasonry or metal B-vent, no power | Electricity and narrow vent pipecan run sideways to a wall |
| Expected lifespan | 8 to 12 yrstank corrosion sets the clock | 8 to 12 yrssame clock, same tank |
Flue already in good shape and mornings are quiet? The atmospheric model is cheaper to buy and the $46-a-year gap will not pay that back fast. Flue is marginal, or two showers overlap most days? The power vent’s extra first-hour rating and lower running cost both earn their keep.
The $46 gap, and the one that actually moves the needle
Start from the heat, not the tank. The household this site models draws 64 gallons a day at a 70 °F rise, which is 136.4 therms of heat that has to land in the water every year no matter which of these two tanks makes it. Divide that by the appliance’s efficiency to see what the gas meter actually records. The atmospheric model at UEF 0.62: 136.4 ÷ 0.62 is about 220 therms, or $330 a year at $1.50 a therm. The power vent model at UEF 0.72: 136.4 ÷ 0.72 is about 189 therms, or $284 a year. That is a $46-a-year gap, $460 over ten years, real but not the kind of number that reorders a decision on its own.
What actually moves the needle is the first-hour rating: 84 gallons from the atmospheric model against 97 from the power vent, a 13-gallon difference that shows up every morning two showers overlap, while the $46 shows up once a year on a bill nobody reads line by line. Quiet mornings, bank the $46 and buy the cheaper tank. Busy ones, the recovery gap is worth more than the running-cost gap ever will be.
What the flue decides before the price does
Whether your house can even take an atmospheric tank is a question about the chimney or B-vent that already serves it, not about which water heater you like the look of. A flue that is undersized, blocked, or shared with another appliance in a way current code no longer allows can rule out the atmospheric option before price ever enters the conversation, and a power or direct vent model sidesteps the whole problem by routing its own exhaust through narrow pipe instead. Figuring out which situation your house is actually in, and what a vent run would require, is a question for a licensed plumber who can see the chimney, not a spec sheet on a page like this one.
Where this verdict is wrong
I would not pay the power vent premium for a household of one or two people whose mornings never overlap. The atmospheric model’s 84-gallon first-hour rating already outruns what they will ever draw, and the $46 a year saved by the more efficient burner takes a long time to cover a higher equipment price. The power vent earns its keep in a busier house, or a flue-constrained one, not as a default upgrade bought on the strength of a slightly better efficiency number.
Sources
- A.O. Smith ProLine atmospheric vent 50-gallon spec sheet (hotwater.com): BTU input, first-hour rating, recovery rate and Uniform Energy Factor for the standard model.
- Lochinvar 50-gallon power vent spec sheet (lochinvar.com): BTU input, first-hour rating and Uniform Energy Factor for the power vent model.
- The modeling assumptions published on the method page: delivered-heat anchor and gas price.
Check the flue before you check a price tag on a 50 gallon gas water heater. Between a standard atmospheric model and a power vent model, the cheaper one to buy is not always the cheaper one to run, and the bigger first-hour rating usually matters more than either dollar figure. Every number on this page comes from the same household and the same assumptions, laid out in full on the method page.