Looking for a 28kW tankless water heater that can supply continuous hot water for a whole house? This guide highlights five solid options, explains who they are best for, and points out any practical limitations. Each product is evaluated for installation needs, output, and energy efficiency to help you choose confidently. Ideal buyers include new home builders, remodel projects, or anyone replacing an aging storage heater with a compact, high-capacity system.
Selected products at a glance:
| Product | Max Flow (GPM) | Best For | Notes |
|---|---|---|---|
| WINTEMP WM27V Plus | Up to 6.5 | 2–4 bathrooms, mild climates | WiFi control; 200A service recommended |
| ThermoMate 27kW | Up to 5.27 | Compact spaces; mid-size homes | High current draw; 200A service recommended |
| ECOTOUCH ECO270B | Up to 5.5 | 2–4 points of use in apartment/small home | Self-modulating; 113A max |
| Rheem RTEX-24 | 24kW, 24kW = ~> depends on rise | All-electric homes; flexible install | Common reference model |
| Stiebel Eltron Tempra 29 Trend | Unmetered flow; robust for whole house | German engineering; quiet operation | Requires proper panel space |
WINTEMP WM27V Plus 27kW Tankless Electric Water Heater
Best for mid-size homes with two to four water fixtures in mild climates. The WM27V Plus delivers up to 6.5 GPM while maintaining stable temperatures through advanced flow control. It requires a 200 Amp household service and three 40 Amp double-pole breakers wired with 8 AWG conductors. The unit includes WiFi control for remote temperature management and an LED display for quick status checks. Use this option when space savings and continuous hot water are priorities, and when your electrical panel has capacity for high-amperage installation. A noted limitation is its reliance on a robust electrical panel; homeowners with older service may need panel upgrade work.
Who this is for: buyers upgrading from a traditional tank to eliminate cold showers, with a dedicated circuit capacity of 200A or more. Why selected: strong balance of hot-water output, smart controls, and space savings for whole-house use.
ThermoMate 27kW On-Demand Electric Water Heater
Best for homes needing reliable hot water with a compact footprint. This model draws up to 114 Amps and commonly requires three 40 Amp double-pole breakers and appropriate 8 AWG wiring, with a recommended panel capacity around 200A. It delivers up to about 5.27 GPM at a 35°F rise, which suits 2–3 bathrooms or moderate climates. Self-modulating technology improves efficiency by reducing power when flow is lower. A precaution: ensure your electrical panel and wiring are sized to handle the startup surge and continuous load, and plan for dedicated circuit space.
Who this is for: households upgrading from a tank-style heater where space is limited and panel capacity is adequate. Why selected: good compatibility with existing 240V circuits while providing steady hot water for day-to-day use.
ECOTOUCH 27kW On-Demand Electric Water Heater ECO270B
Best for two to four use points in smaller homes or apartments needing strong flow with consistent temperature. The ECO270B uses up to 113 Amps and recommends a 200 Amp panel with three 40A breakers. Flow up to 5.5 GPM helps maintain temperature without noticeable fluctuations. Its self-modulating design saves energy and reduces overall operating costs. A caveat: installation requires careful electrical planning and potentially professional help to ensure the panel has enough space.
Who this is for: urban dwellers or small families requiring reliable instant hot water with a compact install. Why selected: strong temperature stability, energy efficiency, and 4-point suitability.
Rheem RTEX-24 24kW Electric Tankless
Best for primary installations where standard 240V service is available and there is room for panel expansion. The RTEX-24 runs on 24kW with the practical requirement of 3 x 40 Amp double-pole breakers and a robust 200 Amp service recommendation. It provides continuous hot water for the whole home, though performance varies with incoming water temperature. The adjustable temperature dial helps tailor output, but keep in mind the cold-water temperature can influence the rise and flow.
Who this is for: homeowners upgrading to on-demand hot water with commonly available 200A service. Why selected: established model with widespread compatibility and straightforward installation in many homes.
VEVOR 27kW Tankless Electric Water Heater
Best for buyers seeking a feature-rich interface and a compact design with digital temperature display and child safety lock. The 27kW unit operates at up to 113A and emphasizes separate water and electricity paths to minimize scale buildup and potential leakage. It is most suitable for homes where precise temperature control matters and there is a clear plan for panel capacity and wiring. Caution: verify electrical panel space and breaker availability before purchase to avoid installation delays.
Who this is for: families prioritizing user-friendly controls and safety features in a high-capacity system. Why selected: advanced temperature display and secure operation with a compact form factor.
Buying Guide
- Electrical service and panel capacity: Most 28kW units require 200A service and three 40A breakers. Confirm the panel has three free circuits and space for a 8 AWG wiring run.
- Flow rate needs: Estimate your peak simultaneous demand (showers, sinks, appliances). Popular ranges are 4–6.5 GPM; pick a model that matches your climate and household size.
- Water temperature rise: In colder climates, the same unit may deliver less GPM due to higher temperature rise requirements. Consider a unit with higher rated GPM if you live in a cool region.
- Installation considerations: Check water connections (3/4″ NPT) and ensure adequate clearance around the unit. Some panels require professional electrical service upgrades.
- Energy efficiency: Self-modulating technology helps save energy by adjusting power to only what is needed at any moment. Look for models with true standby off-state to minimize idle consumption.
- Safety and controls: Features like digital temperature displays, ECO/auto-modulation, and child locks contribute to safer operation and easier tuning for family use.
FAQ
- What size electrical service do I need for a 28kW tankless heater?
Most setups require a 200A service with three 40A double-pole breakers and 8 AWG wiring for each line. Check your panel capacity before purchasing.
- Can I install a 28kW heater in a 2-bedroom home?
Yes, if your climate allows adequate hot water usage and the electrical panel can support the load. Consider a model with 5–6 GPM if you anticipate higher simultaneous demand.
- Will a tankless heater save energy?
Yes, most models use self-modulating technology to adjust power based on flow and temperature needs, reducing standby energy and avoiding constant hot water heating.
- Do these units require professional installation?
Electrical and plumbing work is required; many jurisdictions mandate licensed electricians for electrical connections and permits.
- What if my water is very cold?
Cold incoming water reduces the flow rate at a given temperature rise. Choose a higher-capacity model or plan for staged heating in colder climates.
- Are all 28kW heaters compatible with any home?
No. Compatibility depends on panel space, wiring, and local electrical codes. Always verify with a licensed professional before purchase.