We recommend these products based on an intensive research process that's designed to cut through the noise and find the top products in this space. Guided by experts, we spend hours looking into the factors that matter, to bring you these selections.
Everyone has experienced the hassle of running out of hot water in the middle of a shower or filling the bathtub only to realize the water is cold because you washed dishes 15 minutes ago. These problems are associated with traditional water heaters, which keep a limited supply of hot water at the ready and take a lot of time to replenish, should the hot water be used up.
Thankfully, tankless hot water heaters offer a solution. These appliances are a fraction of the size of traditional heaters and cycle water through heating elements to provide a limitless supply of hot water at the temperature of your choice. Switching to a tankless heater is a great way to modernize your home and enjoy hot water for extended periods.
Our best pick is the Rinnai RU199iN Condensing Tankless Hot Water Heater. It is Energy Star–qualified and able to provide hot water to several appliances at once.
Fuel Type: Electric (240 V) | Flow Rate: 5.9 GPM | Sizing and Usage Needs: Whole-home use, supports multiple fixtures simultaneously | Energy Efficiency: Up to 99.8%, self-modulating
The Rheem RTEX-24 delivers solid performance for homes that need steady hot water without bulky tanks hogging space. With a 5.9 GPM flow rate and 24 kW power, it easily handles multiple fixtures at once; think a couple of showers and a sink running at the same time. The digital temperature control and self-modulating system make fine-tuning easy and efficient, especially when installed close to the point of use.
Setup is straightforward, and users praise the clear instructions and clean wall-mounted design. While most customers report consistent heat and solid reliability, a few mention fluctuations in temperature under high demand. It’s not the flashiest unit out there, but for dependable, on-demand hot water with excellent efficiency, the RTEX-24 is a smart, practical choice.
Fuel Type: Electric (240 V) | Flow Rate: 1.3 to 3.1 GPM | Sizing and Usage Needs: Best for single point-of-use like a shower, sink, or office breakroom | Energy Efficiency: Up to 99.8%, self-modulating
The EcoSmart ECO 11 is a compact solution for anyone needing hot water at a single location without giving up floor space or overpaying on energy bills. It fits neatly on a wall, uses just 13 kW, and still manages to deliver up to 3.1 GPM depending on your inlet water temperature. The digital temperature controls offer one-degree precision, and its self-modulating tech means it only draws power when needed.
We love the easy installation and compact size, especially for tight setups like studio apartments or office sinks. While many users praise its consistency and efficiency, some mention temperature fluctuations or early product failures. For a smaller application where space and energy savings matter, this model offers dependable performance and a clean, low-profile design.
Fuel Type: Propane (Battery ignition, 2 D-cell) | Flow Rate: 1.32 GPM | Sizing and Usage Needs: Portable use for camping, outdoor showers, RVs, or off-grid cabins | Energy Efficiency: Moderate (34,000 BTU/hr)
This is a go-to pick for campers, cabin dwellers, or anyone needing hot water in remote places. Weighing just 10 pounds with a foldable handle, it's designed for grab-and-go use and sets up in minutes. With a 1.32 GPM flow rate and basic flame control, it delivers near-instant hot water for outdoor showers or dishwashing, provided you're not expecting luxury hotel pressure.
It runs on propane and two D batteries, so there's no need for an electrical hookup. Customers love the simplicity and quick heat-up time, though durability is hit-or-miss. Some units run flawlessly for over a year, while others report leaks or flameouts after a few weeks. If you're after a lightweight, affordable hot water solution for above-freezing conditions, this one punches well above its weight in convenience.
Fuel Type: Electric (240 V) | Flow Rate: 4.4 GPM | Sizing and Usage Needs: Mid-size whole-home or multi-point use (1–2 showers or multiple sinks) | Energy Efficiency: Up to 99.8%, self-modulating
The Rheem RTEX-18 strikes a solid balance between performance and practicality for households that need reliable hot water without going overboard on power. With a 4.4 GPM flow rate and 18 kW output, it comfortably supports a shower and a sink running at the same time; ideal for smaller homes or moderate-demand setups. The self-modulating technology ensures energy isn't wasted, adjusting power use based on your actual hot water demand.
Installation is straightforward, and we appreciate the easy-to-read digital temperature controls and compact form factor that frees up valuable space. While it's not meant to power a full household during peak usage, for the right setup, it’s an energy-smart, space-saving workhorse that delivers consistent hot water on demand.
Fuel Type: Natural Gas or Propane | Flow Rate: 11.1 GPM | Sizing and Usage Needs: Whole-home use, supports up to 7 fixtures simultaneously | Energy Efficiency: Ultra-high efficiency, UEF 0.98
The Rinnai RX199iN is a powerhouse that blends commercial-grade performance with smart home readiness. With a flow rate of up to 11.1 GPM and a massive 199,000 BTU output, this unit can keep hot water flowing to multiple showers, sinks, and appliances without breaking stride. Its Smart Sense gas control system automatically adjusts between natural gas and propane, and the Versa Vent design allows for indoor or outdoor installation with ease.
Customers love the consistent water temperature, modern digital controls, and high-end build quality. Installation is best left to a pro, but once it’s in place, you’ll enjoy endless hot water, reduced energy bills, and a compact unit that tucks away neatly. If you’re ready to future-proof your home’s hot water setup, this heater stands tall in performance, efficiency, and flexibility.
Fuel Type: Electric | Flow Rate: Up to 2 sinks (approx. 0.5–1.3 GPM) | Sizing and Usage Needs: Point-of-use (ideal for under-sink use, small bathrooms, handwashing) | Energy Efficiency: 98% thermal efficiency
The Bosch Tronic 3000 T ES2.5 brings compact convenience to the forefront. This electric mini-tank water heater delivers hot water right where you need it, whether you’re washing up in the garage, outfitting a basement bar, or just tired of waiting for the tap to warm up. With a 2.5-gallon tank and the ability to mount it on a wall, shelf, or floor, it’s as flexible as it is efficient.
Users love its fast recovery time and plug-and-play install; just tap into your cold water line and you’re off. The sleek exterior fits neatly under sinks, and while it won’t handle a whole house, it’s perfect for point-of-use jobs. If you're looking to eliminate wait times and save water without breaking the bank, this Bosch unit is a smart, efficient solution.
Fuel Type: Electric | Flow Rate: Moderate (typically supports 1–2 low-flow fixtures) | Sizing and Usage Needs: Best for small apartments, single bathrooms, or point-of-use applications | Energy Efficiency: 99.5%
The Titan N-120 electric tankless water heater is a compact powerhouse designed for energy-conscious homeowners. With dual heating chambers and on-demand water control, it delivers hot water quickly without wasting energy. This unit is ideal for smaller homes or point-of-use setups, and many customers appreciate its space-saving profile and simple wall-mount installation.
Its 11,800-watt heating capacity is enough for a shower and sink combo in warmer regions, though colder climates may see reduced performance. While users often note improved utility bills and solid value, reports on temperature consistency and long-term durability are mixed. For someone looking to cut down on energy use without sacrificing comfort, the Titan N-120 offers a cost-effective entry into the tankless world.
Fuel Type: Electric | Flow Rate: 1-2 showers (approx. 2.5–4.0 GPM) | Sizing and Usage Needs: Whole-home use in small to medium households | Energy Efficiency: 99% efficiency with self-modulating technology
The Stiebel Eltron Tempra 24 Plus electric tankless heater is a space-saving powerhouse that blends interior elegance with performance. Its sleek panel and quiet operation make it feel built just right, while advanced flow control keeps the water temperature consistent, even during simultaneous use across two showers in warm climates.
With nearly 99% efficiency, you’re not tossing energy down the drain, and the long warranties signal confidence in its longevity. You will need a hefty electrical setup, specifically a pair of 50 amp breakers, so check your panel before diving into install. But once it's mounted under the sink or tucked in the garage, you'll wonder how you ever lived without an endless stream of hot water.
Fuel Type: Electric | Flow Rate: Up to 2.3 GPM (varies with inlet temp and flow rate) | Sizing and Usage Needs: Ideal for point-of-use, small homes, apartments, or auxiliary hot water needs | Energy Efficiency: 98% thermal efficiency, self-modulating
This electric tankless water heater proves that big comfort can come in a small package. Its self-modulating tech adjusts power to match your flow, making sure you don’t waste energy or get a surprise blast of boiling water. With its digital display and touch controls, dialing in the perfect temp is as easy as a flick of a switch.
This model is a great fit under the sink or in a tight utility space, and customers say the install is clear cut. Some handle it themselves, while others bring in a pro. It won't serve a full household, but for quick sink or pet-wash action, it’s a smart, compact solution.
Fuel Type: Propane Gas | Flow Rate: Up to 3.6 GPM (supports 2–3 water points like bathroom, kitchen, and bar) | Sizing and Usage Needs: Whole-home use for small to medium households, cabins, or tiny homes
The Ranein 80,000 BTU propane tankless heater is a compact standout that brings instant hot water to your crew without the bulk. Delivering up to 3.6 GPM, it handles a bathroom sink, a kitchen tap, and a bar faucet in stride. The digital preset modes, from fruit wash to infant temp, are a thoughtful touch and save you from fiddling with guesses.
Reviewers love its performance right out of the box and the ease of setup, with one noting it was “awesome right out of the box.” A caution to consider, this unit is best suited to warmer climates, as freeze protection is not built in. A little heat tape solves that quickly. If you're after a no-fuss, space-saving solution that covers basic needs and won’t rob you blind on fuel, this model is a smart pick.
Tankless water heaters only heat water when you need it, so minimal energy is wasted.
The beauty of a tankless water heater is its ability to provide a continuous supply of hot water. Compared to a traditional water heater, a tankless option is more efficient in its delivery and is a big energy saver. A tankless water heater is a heating element (gas or electric) that connects directly to the home’s water pipes. When a hot water tap is turned on, water flows through the element and on to its destination.
Electric heating elements provide a slower flow rate than gas-powered models. A sensor in the heating element turns on the burner, and as water enters the unit, a thermostat springs into action to quickly get the water to the desired temperature.
Gas-driven tankless water heaters need to ventilate through the ceiling and outside the house. Larger tankless systems, called gas-condensing units, are armed with a second heating system. These provide more hot water to homes where the occupants might want to simultaneously use a dishwasher, shower and kitchen sink.
The most important consideration when it comes to choosing the right tankless water heater for you is how you’ll power it. If you don’t have a gas line available, you’re limited to electric heaters unless you decide to have a gas line installed.
Electric heaters will save you money in the long term thanks to their high-efficiency operation, but the high cost of purchase and installation could eat up those savings, depending on how long you plan to live in the home.
Some homes aren’t equipped with the necessary gas or electric connections required for a tankless heater, and having those systems professionally installed could come with a price tag in the thousands of dollars.
Gas models are easily more efficient than traditional tank-based units. However, their efficiency peaks somewhere near 85%, while electric models are more than 90% efficient.
Even though the fuel is generally less expensive than electric energy, many people choose electric models because they last longer and are cheaper to install.
When installing a gas-powered tankless water heater, new vents and ducts must be put in place to ventilate the byproducts of burning gas. If placed in a tight space, installation can be more rigorous due to the need for alternative venting, such as side-wall venting.
Electric models are often smaller and, as such, can be placed in smaller spaces where a gas tankless heater might not fit. An electric unit can be placed closer to the area where hot water is needed, adding to the efficiency and customer satisfaction. The only additional cost for an electrical tankless unit would be if a house’s electric service would need to be updated or remodeled.
It’s important to buy a tankless water heater with the capacity to meet your simultaneous hot-water demands. A small model won’t be able to supply a clothes washer, shower and kitchen sink at the same time. Before you purchase, try to anticipate scenarios where multiple appliances would need hot water at the same time. Check manufacturer ratings and customer reviews to determine whether the model you’re considering would provide enough water during your high-demand times.
No convenient space inside the house for a tankless water heater? Conveniently, some models are designed to be mounted on the outside of the house.
Mounting a heater outside requires additional consideration, however. If you live in a climate where temperatures dive below freezing, you need to take special maintenance measures so frozen pipes don’t damage your appliance. Notably, without Wi-Fi controls installed, making adjustments to your heater would require you to take trips outdoors.
If it’s low maintenance you want, an electric tankless water heater is your best bet.
Every six months, the unit should be flushed with white vinegar to break up any mineral deposits that hard water may leave behind. The appliance’s filter should also be soaked in white vinegar during this process. The manual that comes with your unit will provide instructions on how to access the filter and flush the internal components appropriately.
Keeping your heater free from lime and mineral buildup helps ensure that the water flows freely and makes contact with its heating elements.
While there are models in this low-price band, they come with a lot of limitations. Some are only powered by propane, which adds complexity to the installation and ongoing use. Others are geared toward warmer climates and instances where only one usage (such as a sink) is needed.
In this price range, some models use propane fuel or are built for a single purpose, such as an outdoor shower. There are also some electric tankless models with lower wattages, which translates to less power. Units acceptable for smaller homes in temperate climates can be found in this range.
Electric tankless water heaters in this price range deliver better performance. For example, you are likely to get greater efficiency and more water flow on demand. Some models must be installed close to the point of use (within 50 feet), but that is offset by the fact most claim to be easy self-installs.
These models provide greater flow capacity, and they’re more likely to offer additional features, such as digital temperature settings and Wi-Fi.
If you want a unit that will provide a lot of hot water on demand with a strong flow to multiple points of use, it will cost you $500 to $2,000. Along with the everyday excellent performance, these premium models typically have longer warranties, top-tier customer service and great durability.
A. For best results, manufacturers recommend that you turn the hot water on high, allow the water to heat, then cool the delivered water by opening the cold-water tap. This allows the tankless water heater to run at top efficiency while you make fine adjustments via the amount of cold water being mixed in.
A. Most tankless water heaters reach their peak temperature and start heating the water within seconds of tap activation. The slight lag you experience in receiving hot water depends mostly on the distance between the heater and the tap.
A. Most electric tankless water heaters will still allow water to flow when your power is out. However, the heating element won’t warm the water unless you have a battery backup or some other source of electricity, like a generator.
A. Altitude matters for tankless units. At 4,000 feet, a gas unit begins to lose its efficiency at a rate of 4% per 1,000 feet. Electric models are not affected.
A. In addition to the high price and expensive installation, another downside to tankless water heaters is that they can only heat so much water at a given time. While the supply may be endless, running too many appliances at once could result in temperature fluctuations if the unit is unable to keep up with the demand.
We researched dozens of options before narrowing our list down to the five best tankless water heaters. We weighed the pros and cons of gas versus electric models and indoor versus outdoor options. We looked at specs such as voltage, size, the number of water connections and output temperature range. And naturally, we factored in the cost of each model and explored whether it offered enough quality and features to justify the price.
Using a combination of in-house testing, trusted consumer feedback and a shared thrill of seeking out the absolute best products, devices and tools, BestReviews is your number-one resource when it comes to reviews you can count on. Our staff brings you real advice from people who share your passions and seek to make every day a little easier, a little better and a lot more fun.
Derek Walborn is one of BestReviews’ trusted lawn, garden and DIY experts. Providing insight since 2021, Derek has written extensively on topics that range from home security systems and propane grills to the latest power tools and home improvement gadgets.
