Answering the question, which tankless water heater is most efficient for your home? This guide compares top options by efficiency and performance, helping buyers choose based on household size, fuel type, and installation needs. The best fits include compact electric and gas models for small spaces, mid-size homes, and multi-fixture living. The table below highlights five strong choices with clear pros and limitations so you can select the right model for your usage pattern.
Summary table of chosen products
| Product | Fuel Type | Approx. Flow (GPM) | Best For |
|---|---|---|---|
| 14kW Tankless Water Heater (ORBEK) | Electric | 3.38 | Compact apartments, point-of-use upgrades |
| Rinnai RE199iN | Natural Gas | 9.8 | Whole-house comfort, mid-to-large homes |
| Stiebel Eltron Tempra 29 Plus | Electric | 28.8kW equivalent | Larger electric setups, energy efficiency |
| APUS Propane Tankless | Propane | 4.42 | High flow with flexibility, off-grid options |
| Rheem RTG Series | Liquid Propane | 8.4 | Indoor LP installations, high demand |
14kW Electric Tankless Water Heater — ORBEK
The ORBEK 14kW electric unit provides on-demand heating with 3.38 GPM flow and ±1°F precision control, offering high efficiency at point-of-use. This compact heater is suitable for smaller spaces where a full-size water heater is impractical. Best for single-family apartments or supplemental hot water in cottages where electric service can support a 240V setup.
Best for: small homes, apartments, or upgrades where space is at a premium and 3.38 GPM meets typical shower-and-sink needs. Caution: performance may vary with cold-water input in colder climates; ensure your electrical panel and wiring can handle 14kW continuous draw.
Rinnai RE199iN Non-Condensing Gas Tankless
This non-condensing gas model delivers up to 9.8 GPM and 199,000 BTU, supporting multiple fixtures with reliable indoor installation. It includes an LED display for diagnostics and a long-term reliability profile, making it a solid choice for whole-house hot water in many homes.
Best for: mid-to-large homes needing continuous hot water for several fixtures. Limitation: non-condensing design means energy efficiency is good but may be outpaced by condensing competitors in some installations; ensure compatibility with existing venting and controls.
Stiebel Eltron Tempra 29 Plus Electric
Stiebel Eltron’s Tempra 29 Plus is a German-made electric model designed for on-demand heating with advanced flow control. Its two temperature memory presets and 28.8kW-class draw provide scalable performance for larger electric systems without a storage tank. Space-saving design eliminates venting requirements in many installations.
Best for: households upgrading to electric on-demand without gas lines, or where a compact but capable electric solution is desired. Caution: requires hard-wired 240 or 208-volt service with substantial electrical capacity; confirm panel space before purchase.
APUS Propane Tankless Water Heater — 95,000 BTU
The APUS propane unit offers 95,000 BTU with 4.42 GPM, designed to deliver stable temperatures with ±1°F precision. It uses oxygen-free copper heat exchangers and segmented combustion technology to achieve up to 98% thermal efficiency (UEF 0.81). Ideal for households that need steady hot water for two showers plus a sink.
Best for: homes where propane is readily available and higher flow is required. Caution: propane units require proper ventilation and outdoor installation considerations; verify local code compliance and space for venting if applicable.
Rheem RTG Series LP Tankless Water Heater
Rheem RTG Series provides an 8.4 GPM capacity with indoor LP operation and non-condensing efficiency. It targets households wanting reliable on-demand hot water with a straightforward installation in spaces where natural gas is not available. The model supports continuous hot water without a storage tank.
Best for: homes with existing LP gas supply and higher daily hot water needs. Caution: non-condensing design means venting and limited energy savings compared with condensing variants; consider long-term operating costs and venting requirements.
Buying Guide: Key Considerations For Tankless Water Heaters
- Fuel type and availability: Choose electric, natural gas, or propane based on what is accessible in your area and the cost of energy. Electric units are typically easier to install in apartments, while gas models suit whole-house setups.
- Flow rate needs: Estimate the total GPM required for simultaneous hot water use (showers, sinks, appliances). Higher GPM models support more fixtures at once but may require larger electrical panels or gas lines.
- Efficiency metrics: Condensing designs usually achieve higher efficiency by reclaiming heat from exhaust. Review UEF or BTU efficiency ratings where available, and compare standby losses to tank alternatives.
- Ventilation and installation space: Gas units often need venting and space for intake/exhaust runs. Electric models may fit compact spaces but require electrical capacity. Consider indoor vs. outdoor installation constraints.
- Warranty and service: Look at heat exchanger warranties and parts coverage. Long-term reliability often ties to the quality of construction and ease of maintenance, not just initial efficiency.
- Control and diagnostics: LED displays, diagnostics, and smart-home compatibility can simplify maintenance and monitoring. If you want remote management, check for module compatibility and app support.
FAQ
- What efficiency should I look for in a tankless water heater? Look for high energy-efficiency ratings such as favorable UEF or condensing design advantages, along with low standby losses and precise temperature control.
- Do I need venting for electric tankless heaters? No, electric units typically do not require venting, which can simplify installation in apartments or condos.
- Is a higher GPM always better? Not always. Choose a GPM that matches peak simultaneous usage in your home; oversizing adds cost without benefit if you seldom reach the maximum flow.
- Can I install a tankless heater myself? Installation often requires professional electrical, gas, or venting work. Check local codes and safety standards; improper installation can void warranties and create hazards.
- Which fuel type is most cost-effective? Costs vary by region. In some areas, gas may be cheaper than electricity; in others, electric heat may be more economical and easier to justify for smaller homes.
- Do tankless heaters provide endless hot water? They can supply hot water on demand, but flow and temperature stability depend on the unit’s capacity and incoming water temperature.