AO Smith and Rheem are the two dominant US residential water heater brands — combined ~70% of the market. They compete directly at every tier. Picking between them comes down to retailer channel, warranty terms, and installer preference.
The tier-by-tier matchup
| Tier | AO Smith | Rheem | Edge |
|---|---|---|---|
| Premium gas tank 50G | Signature Premier (9-year) | Performance Platinum (12-year) | Rheem on warranty length |
| Premium tank — anode | Coregard (slower deplete) | Aluminum-zinc | AO Smith on anode |
| Premium tank — WiFi | iCOMM | EcoNet (more mature) | Rheem on smart-home |
| Heat pump 50G | Voltex 50G (10-year) | ProTerra 50G (10-year) | Tie |
| Premium gas tankless | ProLine Tankless 10 GPM (15-year HX) | RTGH-95DVLN (9.5 GPM, 12-year HX) | AO Smith on flow + warranty |
| Lifetime tank | No equivalent | Marathon (limited lifetime) | Rheem — unique |
| Contractor channel | ProLine Master (10-year) | Professional Classic Plus (8-year) | AO Smith on warranty |
| Primary retailer | Lowe's | Home Depot | Tie — by retailer preference |
Specific product matchups
AO Smith Signature Premier 50G Gas vs Rheem Performance Platinum 50G Gas
Rheem wins on warranty (12 vs 9 years) and EcoNet WiFi standard. AO Smith wins on Coregard anode (longer-lasting) and Hydrojet sediment management. Price within $100. Pick Rheem for warranty math + smart-home; AO Smith for build-quality emphasis.
AO Smith Voltex 50G HP vs Rheem ProTerra 50G HP
Spec-equivalent. Same warranty, same UEF (3.42 vs 3.45 — wash), same 67 GPH FHD. Rheem ships EcoNet, AO Smith ships iCOMM. Pick by retailer (Lowe's = Voltex; Home Depot = ProTerra).
AO Smith ProLine Tankless 10 GPM vs Rheem RTGH-95DVLN
AO Smith wins on flow (10 vs 9.5 GPM) and warranty (15 vs 12 years). Rheem wins on EcoNet integration. Pick AO Smith for spec/warranty; Rheem for smart-home.
Bottom line
For most buyers, the choice is retailer + installer preference. AO Smith wins on tankless warranty + Coregard anode + ProLine Master plumber-channel. Rheem wins on premium tank warranty + Marathon lifetime + EcoNet WiFi. Both are competitive across the lineup.
For the alternative comparison see AO Smith vs Bradford White. For broader context see our AO Smith lineup.