Rheem Gladiator vs A. O. Smith Signature 100
One is the safest electric tank on the retail shelf. The other delivers half as much hot water again. They are not competing on the same axis.
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If you have a gas line, the A. O. Smith Signature 100 wins on output — a 91-gallon first-hour rating from 50 gallons, against 63 for the Rheem Gladiator. If the heater is electric, or sits above a finished room, the Gladiator wins on risk: 360° leak detection with a factory-fitted automatic shutoff that limits a leak to no more than 20 ounces, plus a 12-year tank and parts warranty with 3-year labor.
These two come up together because they are what a homeowner sees side by side at the same nominal 50 gallons. They are not interchangeable. One burns gas up a flue and recovers fast; the other runs on 240 V, recovers slowly, and protects the ceiling underneath it.
Side by side on published figures
| Rheem Gladiator 50 | A. O. Smith Signature 100, 50 gal gas | Rheem Performance Platinum 50 | |
|---|---|---|---|
| Fuel | Electric, 240 V | Natural gas | Electric, 240 V |
| Capacity | 50 gallons | 50 gallons | 50 gallons |
| Heat input | 5,500 W double element | 50,000 BTU/h ultra-low NOx (a 40,000 BTU version is also sold) | 240 V elements |
| First-hour rating | 63 gallons | 91 gallons (77 on the 40,000 BTU model) | 63 gallons |
| Recovery | Not published separately | Not published separately | 21 gal/h at a 90°F rise |
| Efficiency | 0.92 UEF | Not published on the retail listing | 0.93 UEF |
| Leak protection | 360° LeakSense with auto shutoff; leaks limited to 20 oz | None | None |
| Venting | None | Atmospheric — chimney or B-vent required | None |
| Dimensions | Not published on the retail listing | 61 in H x 22 in dia (50,000 BTU model) | Short and tall variants |
| Warranty | 12-year tank and parts, 3-year labor | 6-year tank and parts with 1-year labor; 9-year with 2-year labor on the 40,000 BTU model | Not published on the spec sheet we hold |
Quick picks
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| # | Product | Best for | Price |
|---|---|---|---|
| 1 | Rheem Gladiator 50 gal electricThe electric tank to put above a finished floor: integrated leak detection with an automatic shutoff valve that limits a leak to around 20 ounces, plus a 12-year tank and parts warranty. | Electric tanks in finished spaces | Check price on Amazon No live price feed on this site, so we show none. #ad |
| 2 |  A. O. Smith Signature 100, 50 gal gasThe straightforward 50-gallon gas replacement, and the reason to pay attention to the burner size: the 50,000 BTU version is rated at a 91-gallon first-hour rating against 77 gallons for the 40,000 BTU one. | Most gas tank replacements | Check price on Amazon No live price feed on this site, so we show none. #ad |
| 3 |  Rheem Performance Platinum 50 gal electricA plain, well-warranted 50-gallon electric tank: a 63 gallon-per-hour first-hour rating, 21 gallons per hour of recovery at a 90°F rise, and a 0.93 UEF. | Straight electric replacement | Check price on Amazon No live price feed on this site, so we show none. #ad |
The three tanks in full
Pick 1 — Electric tanks in finished spaces
Rheem Gladiator 50 gal electric
The electric tank to put above a finished floor: integrated leak detection with an automatic shutoff valve that limits a leak to around 20 ounces, plus a 12-year tank and parts warranty.
| Capacity | 50 gallons |
|---|---|
| Elements | 5,500 W double element, 240 V |
| First-hour rating | 63 gallons |
| Efficiency | 0.92 UEF |
| Leak protection | 360° LeakSense detection with factory-fitted automatic shutoff; leaks limited to no more than 20 oz |
| Warranty | 12-year tank and parts, 3-year labor |
What is good
- The auto-shutoff valve is the single most valuable feature on any tank installed over drywall
- 12-year tank and parts with 3-year labor is among the longest electric warranties sold at retail
- 5,500 W double element gives faster recovery than the usual 4,500 W pair
- Leak alerts arrive before the ceiling does
What is not
- A 63-gallon first-hour rating from 50 gallons is ordinary — electric recovery is slow, full stop
- Running cost is electric-rate running cost; a heat pump model costs far less to run
- The shutoff valve is one more serviceable part in the cold inlet
Skip it if: Skip it if the heater lives on a concrete slab next to a floor drain and you have the headroom for a heat pump model. You are paying for leak protection you can get from a 20-dollar pan, and giving up the running-cost saving a heat pump would deliver.
No live price feed on this site, so we show none. #ad
Specifications above from Home Depot listing, Rheem Gladiator XE50T12CS55U1. We have not tested this unit ourselves.
Pick 2 — Most gas tank replacements
A. O. Smith Signature 100, 50 gal gas
The straightforward 50-gallon gas replacement, and the reason to pay attention to the burner size: the 50,000 BTU version is rated at a 91-gallon first-hour rating against 77 gallons for the 40,000 BTU one.
| Capacity | 50 gallons |
|---|---|
| First-hour rating | 91 gallons (50,000 BTU model); 77 gallons (40,000 BTU model) |
| Burner | 50,000 BTU/h ultra-low NOx, or 40,000 BTU/h |
| Dimensions | 61 in H x 22 in dia (50,000 BTU); 60-3/4 in H x 22 in dia (40,000 BTU) |
| Warranty | 6-year tank and parts with 1-year labor (50,000 BTU); 9-year tank and parts with 2-year labor (40,000 BTU) |
What is good
- A 91-gallon first-hour rating from a 50-gallon tank covers back-to-back showers that empty an electric tank of the same size
- Widely stocked at Lowe's, so same-day replacement is realistic when the old one fails
- Ultra-low NOx burner meets the stricter air-district rules in California and Texas
- 22-inch diameter fits most existing alcoves without re-plumbing
What is not
- The longer 9-year warranty is on the smaller burner, so warranty and recovery pull in opposite directions
- Atmospheric venting needs a working chimney or B-vent
- Standing pilot and flue losses mean it idles energy away all day
Skip it if: Skip it if your water heater sits in a sealed closet or a space with combustion air problems. An atmospheric gas tank needs real combustion air and a real flue — the power-vent or direct-vent models exist for exactly that case.
No live price feed on this site, so we show none. #ad
Specifications above from Lowe's listing, Signature 100 50-gal 50,000 BTU; Lowe's listing, Signature 100 50-gal 40,000 BTU 9-year. We have not tested this unit ourselves.
Pick 3 — Straight electric replacement
Rheem Performance Platinum 50 gal electric
A plain, well-warranted 50-gallon electric tank: a 63 gallon-per-hour first-hour rating, 21 gallons per hour of recovery at a 90°F rise, and a 0.93 UEF.
| Capacity | 50 gallons |
|---|---|
| First-hour rating | 63 gallons per hour |
| Recovery | 21 gallons per hour at a 90°F rise |
| Efficiency | 0.93 UEF |
| Voltage | 240 V |
What is good
- Publishes recovery at a stated temperature rise, which most retail listings do not
- 0.93 UEF is at the top of what a resistance tank can do
- Drop-in replacement dimensions for the previous generation
- Available in short and tall variants
What is not
- 21 gallons per hour of recovery is a third of what a gas tank does
- No leak detection on this model
- Resistance heating is the most expensive way to make hot water in most of the country
Skip it if: Skip it if you have 7 feet of headroom and an unconditioned space to put it in. A heat pump model in that spot uses roughly a third of the electricity for the same hot water, and the payback is measured in a few years, not decades.
No live price feed on this site, so we show none. #ad
Specifications above from Home Depot specification sheet, Rheem Performance Platinum electric (PDF). We have not tested this unit ourselves.
Why the Gladiator exists
Every tank eventually leaks. The Gladiator is the retail answer to what happens when yours does it above a finished ceiling: the unit senses water at the base and closes a factory-fitted valve in the cold inlet, and Rheem rates the resulting spill at no more than 20 ounces. A drain pan plumbed to a drain does a similar job for a fraction of the money — but only if there is a drain to plumb it to, and upstairs laundry closets usually have neither.
- 12-year tank and parts with 3-year labor is among the longest electric warranties sold at retail.
- 5,500 W double element recovers faster than the usual 4,500 W pair, though a 63-gallon first-hour rating is still ordinary.
- No gas, no flue, no combustion air, so it goes in a closet a gas tank cannot legally occupy.
- The shutoff valve is one more serviceable part sitting in the cold inlet — a real, if small, cost.
Why the Signature 100 wins where it can be installed
Ninety-one gallons in the first hour from a 50-gallon tank is the figure that ends arguments about running out of hot water, and it is the burner doing it rather than the storage. Gas puts energy into the tank far faster than a pair of resistance elements, so the tank refills while you are still drawing from it. The 22-inch diameter matters too: it drops into most existing alcoves without re-plumbing, and the unit is stocked at Lowe's, so a Saturday failure can be a Saturday replacement.
The condition that flips the answer
Gas wins on output until the installation says otherwise. An atmospheric gas tank needs a working chimney or B-vent and real combustion air, so if your heater lives in a sealed closet, an interior room or a tightly built modern house, the Signature 100 is off the table and the choice is between electric tanks — or a direct-vent gas unit instead. Water heater venting covers which category you are in, and gas vs electric water heaters covers the running-cost side.
What to buy
| Your situation | Pick | Why |
|---|---|---|
| Gas line, chimney or B-vent, 3+ people | A. O. Smith Signature 100, 50,000 BTU | 91-gallon first-hour rating; nothing electric at this size comes close |
| Electric only, tank above a finished room | Rheem Gladiator 50 | Auto shutoff limits a leak to about 20 ounces; 12-year tank and parts |
| Electric only, slab floor with a drain nearby | Rheem Performance Platinum 50 | 0.93 UEF and the same 63-gallon output; a pan does the leak job for less |
| Gas, want the longest warranty | Signature 100, 40,000 BTU | 9-year tank and parts with 2-year labor, at a 77-gallon first-hour rating |
| Sealed closet, no combustion air | Neither — a direct-vent or power-vent gas tank | Atmospheric venting is the disqualifier, not the brand |
| Unconditioned space with 7 ft of headroom | A heat pump water heater | More first-hour output than either, at a fraction of the electric running cost |
What goes in with it
A water heater is a system, not a box. These are the parts that go in with it, and the ones people discover they need halfway through the job.
- Expansion tank
Required by code on a closed system, which is most homes with a pressure-reducing valve.
- Drain pan
Cheap insurance anywhere the tank sits above something you care about.
- Anode rod
The part that decides when the tank leaks. Replacing it is the highest-value hour of maintenance there is.