Marathon and Stiebel Eltron compete only loosely — Marathon is a storage tank brand; Stiebel Eltron\'s flagship Tempra Plus is whole-house electric tankless. The decision is really storage vs tankless rather than brand-vs-brand.
Different products entirely
| Marathon MR50 (storage) | Stiebel Tempra 29 Plus (tankless) | |
|---|---|---|
| Type | Storage tank | Whole-house tankless |
| Capacity | 50 gallons stored | Continuous flow, no storage |
| Element wattage | 4500W upper + lower (non-simultaneous) | 28.8 kW (continuous output) |
| Breakers | 1× 30A double-pole | 3× 50A double-pole |
| Service panel impact | Modest — single 30A circuit | Major — high amperage continuous draw |
| Tank warranty / heat exchanger warranty | Lifetime tank | 7-year heat exchanger |
| Maintenance | Minimal — no anode rod | Annual inlet filter clean, descaling in hard water |
| Typical price | $1,299-1,599 | $849-1,049 |
| Lifespan | 20-30+ years | 15-20+ years |
Storage vs tankless tradeoffs
Storage (Marathon) wins on
- Simultaneous demand — stored hot water buffers shower + dishwasher + laundry concurrent use
- Lower electrical demand — single 30A circuit vs three 50A circuits
- Service panel friendliness — fits in most existing electrical services without upgrade
- Simpler operation — no flow sensor, no modulation, no inlet filter
- Cold-climate reliability — stored water is always at temp regardless of flow
- Lifetime tank warranty
Tankless (Stiebel) wins on
- Infinite hot water within capacity — never runs out (but capacity is limited)
- Smaller footprint — wall-mount vs floor-stand tank
- Lower standby losses — no stored water cooling between uses
- Slightly longer warranty if you only care about heat exchanger (7-yr Stiebel vs no heat exchanger to fail on Marathon)
- Flow Control technology maintains temperature stability
Cold-climate consideration
This is critical: in cold climates, whole-house electric tankless requires high kW capacity AND adequate electrical service. Tempra 29 Plus needs three 50A 240V circuits = 150A continuous draw. Many 200A residential services don\'t have spare capacity.
Marathon\'s 50-gallon storage tank needs a single 30A circuit. Pre-heated water buffers cold incoming temperature; the stored 120°F water reaches the tap regardless of incoming water temperature.
For cold-climate homes with marginal electrical service, Marathon may be the only viable electric water heating choice.
When to choose Marathon over Stiebel Tempra Plus
- Service panel can\'t support whole-house electric tankless
- Want long-term ownership with lifetime tank warranty
- Anti-maintenance preference (no annual filter/descaling)
- Cold climate with adequate storage capacity
- Aggressive water — Marathon composite handles it; Stiebel still needs descaling
- Lower simultaneous demand — storage handles burst use better than tankless
When to choose Stiebel Tempra Plus over Marathon
- Adequate electrical service for whole-house tankless
- Want never-runs-out hot water within capacity
- Smaller footprint required
- Modern home with new electrical service planned
- Energy-efficiency priority — Tempra eliminates standby losses
- Cold-climate Flow Control technology specifically
Combine both?
Some hybrid installs use both: a Marathon main tank for whole-house storage, with Stiebel point-of-use (DHC or Mini) at distant fixtures for instant hot water and reduced wait times. This is a high-end install pattern. Not common, but possible.
Bottom line
Storage vs tankless decision, not brand-vs-brand. Marathon if you want lifetime composite tank durability with modest electrical demand. Stiebel Tempra Plus if you want whole-house tankless with Flow Control technology and have the electrical service to support it. Both can be the right answer — depends on your install profile.