The best electric tankless water heater for 100 amp service is the EcoSmart ECO 27, offering on-demand hot water and energy efficiency for smaller homes.
Struggling with lukewarm showers because your old water heater can’t keep up? Worried your 100-amp electrical panel can’t handle a powerful upgrade? The right electric tankless water heater for 100 amp service can solve both problems—delivering endless hot water without overloading your system. In this guide, we’ll cover top-rated models, installation tips, and energy-saving insights. For maintenance advice, check our guide on tankless water heater descaling.
Key Takeaways
- Rheem RTEX-13 (13 kW) is the best fit for 100A panels, drawing 54.2A at 240V.
- Prioritize self-modulating technology to reduce energy waste and electrical load.
- Ensure proper wire gauge (6 AWG) and double-pole breaker for safe installation.
- Smaller households (1-2 people) benefit most; larger homes may need a hybrid system.
Top Picks for 100-Amp Compatible Units
Rheem RTEX-13 (13 kW, 240V, 54.2A) fits 100A service. This model balances performance and efficiency, providing 3.17 GPM at a 45°F temperature rise—ideal for apartments or small homes. Its compact design and digital temperature control make it user-friendly. Competitors like the Stiebel Eltron DHC 6-6 (6 kW) suit low-demand setups but lack whole-house capacity.
Comparison Table
| Model | Power (kW) | Amperage | Flow Rate (GPM) |
|---|---|---|---|
| Rheem RTEX-13 | 13 | 54.2A | 3.17 |
| EcoSmart ECO 11 | 11 | 46A | 2.6 |
| Stiebel Eltron DHC 6-6 | 6 | 25A | 1.5 |
Installation Requirements
For a 100-amp panel, avoid units exceeding 80% of capacity (80A continuous load). The Rheem RTEX-13 uses 54.2A, leaving room for other appliances. Key steps:
- Upgrade wiring to 6 AWG copper for 60A circuits.
- Install a 60A double-pole breaker (consult an electrician).
- Ensure proper grounding—faulty wiring risks NFPA violations.
Energy Efficiency & Cost Savings
Tankless heaters save 24–34% on energy bills compared to tanks, per the U.S. DOE. The Rheem RTEX-13’s self-modulating technology adjusts power based on demand, reducing idle consumption. For colder climates, pair with a recirculation pump (installation guide here).
FAQ
1. Can I run a 24 kW unit on 100-amp service?
No—24 kW units require 100A alone, exceeding panel capacity. Opt for ≤13 kW models.
2. Do tankless heaters work in freezing climates?
Yes, but install freeze protection kits and insulate pipes to prevent damage.
3. How long do these units last?
15–20 years with annual descaling (see maintenance tips).
Final Thoughts
Choosing the right electric tankless water heater for 100 amp service ensures hot water without electrical upgrades. The Rheem RTEX-13 strikes the best balance of power and efficiency. For larger households, consider a gas tankless or heat pump hybrid system. Need help? Bookmark our heater guides for expert advice.
