You may be looking for a new hot water tank or moving into a new property and considering your options. Whatever your reason, choosing to go to a tankless water heater system can be a great choice for your home. There are some real benefits to choosing this option over more traditional systems and we\u2019ve put together an overview of tankless water heaters, what to consider when buying one and reviewing the top 10 on the market right now. Our Top Picks Best Tankless Heaters of 2021 Tankless Heaters that are worth mentioning: Our top 10 tankless water heaters We\u2019ve put together a list of the 10 best tankless water heaters on the market right now, including both gas and electric options. 1. Rinnai RUR98iN Ultra Series Condensing Indoor Natural Gas Tankless We start off our list with probably one of the best gas tankless water heaters that you can get for your home. Performance: With an energy efficiency factor of 96% and a flow rate of 9.8 GPM, it is a powerhouse of a water heater. Features: It has some added features that really help this stand out, including freeze protection for temperatures as low as -4 degrees Fahrenheit for indoor models like this one. Furthermore, it has a wifi feature that allows the homeowner to check and change settings whenever they are connected. Budget: You will not be disappointed by this model but do bear in mind that it is one of the most expensive on the market. So if you have a small home or budget constraints, you may wish to look at alternatives. Pros Cons \tAn impressive energy efficiency factor of 96% \tA strong flow rate of 9.8 GPM that will meet all household requirements \tFreeze protection and wifi connectivity \tAn expensive unit which might be more than is required for smaller properties \tIt will require venting and doesn\u2019t come with everything you need 2. Rinnai RUC98iN Ultra Series Natural Gas Tankless Water Heater, Concentric\/Twin Pipe Installation Another on our list from Rinnai, one of the leading manufacturers of gas-powered tankless water heaters. Performance: Once more, they have delivered on both efficiency and power, with this unit providing a flow rate of 9.8 GPM and efficiency factor of 96%. Temperatures: This model really stands out in its ability to provide unlimited amounts of hot water to your home, with a temperature increase of 50 degrees Fahrenheit. This means that even in colder temperatures, you will still get a supply of hot water to faucets and the shower. Installation: It is important to note that we recommend you get some professional assistance with the installation of this model, due to it needing to be connected to a natural gas supply. Once set up, it can take up to 20 seconds to heat the water up, but then you will be enjoying the hot water and reduced energy bills. Pros Cons \tPowerful enough for almost every household \tA fast flow rate of 9.8GPM \tFantastic build quality from an industry-leading manufacturer. \tAn expensive system and maybe too much for some households \tIt will require ventilation, which may mean further costs. 3. Stiebel Eltron Tempra Plus 24 kW, Tankless Electric Water Heater The first electric tankless water heater on our list comes from Stiebel Eltron and this model doesn\u2019t disappoint. Flow Rate: A small, lightweight unit that provides a strong flow rate of 4.0 GPM and will heat up your water to impressive levels. Installation: What really makes this model stand out is just how easy it is to install in your home, being small enough to fit under a sink or in a small closet. Performance: It has a simple digital control panel to help check settings and make changes when you need and utilises solar power to help run efficiently. However, if you want to power an entire household, then you will need to consider buying multiple units. Pros Cons \tA top flow rate for electric tankless water heaters, of 4.0 GPM \tSleek and stylish means it will fit in almost any location \tSimple to install and comes with a good manufacturers warranty \tThis is one of the more expensive electric systems \tTo power a household, you will have to buy multiple units 4. EcoSmart ECO 27 Electric Tankless Water Heater 27 KW at 240 Volts We love when systems work efficiently and this one lives up to its manufacturer\u2019s name of EcoSmart. For those wanting a straight forward, small electric tankless water heater for a kitchen or bathroom, then look no further. Performance: With a maximum flow rate of 3GPM, it can even work with very cold incoming water, boosting the water temperature by 50 degrees Fahrenheit, at a lower flow rate of 1.5 GPM. We appreciate this isn\u2019t near the speed of the larger gas units, but for a single faucet, it is one of the most efficient units there is. Installation: Despite it being on the small size when compared to some other models, it is larger than you\u2019d expect, so you will need to think about what space you have before making the purchase. Pros Cons \tA very efficient unit that provides a good flow rate of 3.0 GPM \tVery easy to install and get up and running quickly \tA simple digital control panel that allows you to change settings easily \tit won\u2019t have the flow rate of bigger systems or gas systems \tSlightly bigger than expected 5. Rheem RTGH-95XLN Prestige Natural Gas Outdoor Tankless Water Heater This is one of the outdoor gas tankless water heaters to make it onto our list and from the outset, we want to say how impressive this model is. Performance: It has a flow rate of 9.5GPM, energy efficiency factor of 94% and can actually be connected to other units if you want to increase the overall water heating system in your house. Design: Rheem has used high-quality, stainless-steel to protect it from the elements and with no ventilation required, you can get set up relatively easily and it will meet the needs of the majority of households. Pros Cons \tAn impressive energy efficiency of 94% \tA flow rate of 9.5 GPM \tNo ventilation required when installing this unit \tThe initial cost is high but over time it\u2019s energy efficiency makes it a cost-effective unit. 6. Rheem RTG-84XLN Outdoor Tankless Natural Gas Water Heater The second of the Rheem outdoor gas tankless water heaters on our list now and this model is definitely a great choice for any household. Performance: This is a more budget-friendly unit but still boasts some impressive statistics, with a flow rate of 8.4 GPM and an energy efficiency rating of 84%. This means it will do a good job for most households, except perhaps for some much larger or high usage properties. Emissions: It\u2019s low emissions and performance will mean you will be reducing your carbon footprint whilst also saving money, a combination we love! Features: They\u2019ve even thrown in a remote control system that means you can change settings without having to go outside. Pros Cons \tHigh-quality design and build from a leading manufacturer \tA flow rate of 8.4 GPM \tNo ventilation required and remote-controlled settings. \tNot as powerful as other units on the market 7. Takagi T-KJr2-IN-NG Indoor Natural Gas Tankless Water Heater This gas tankless water heater is one of the more affordable models on our list, that still packs a punch in terms of quality and performance. Performance: With a flow rate of 6.6 GPM and an energy efficiency factor of around 83%, you know it will do the job for most normal sized households. However, it is important to note it isn\u2019t as efficient or powerful as other models, so you may need to consider an alternative if you have a larger or busier household. Budget: For people on a budget and with limited space, this is a great fit as it is one of the smallest gas systems available right now. Maintenance: You will get an impressive 10-year manufacturers warranty with this model and it is very easy to maintain, should you need to make any repairs or replace parts. Pros Cons \tOne of the most cost-effective solutions on the market \t10-year manufacturers warranty \tCompact size is perfect for smaller properties \tIt does make quite a bit of noise compared to other systems \tIts reduced flow rate and energy rating may not be enough for some properties 8. Rheem 95DVLN Indoor Direct Vent Tankless Water Heater Another tankless water heater from Rheem now but this one is their indoor model. One of the first things you will notice about this model is its fantastic flow rate of 9.5 GPM, one of the best rates you will see right now Ventilation: The manufacturers have put in a low NOx system which means it doesn\u2019t need the traditional heavy-duty venting systems. Installation: It can be installed pretty much anywhere and basic PVC venting will do the job, reducing complication and costs significantly. Efficiency: An efficient unit that does use a fair amount of power but thanks to this efficiency, you don\u2019t need to worry. Do bear in mind that when the water comes into the house at a much colder temperature, it can take a few moments for this system to heat the water up Pros Cons \tA low NOx system that reduces emissions \tA powerful flow rate of 9.5 GPM \tEasy to install and use thanks to its digital display \tOne of the more expensive models on our list 9. Takagi T-H3-DV-N Tankless Water Heater The most powerful unit to make it onto our list, with a flow rate of 10 GPM. This tankless water heater from Takagi really does deliver the goods. Ventilation: What is interesting about this model is that it works by condensing steam that is produced, which turns it into water which can be drained out. This means you can safely operate this gas heater indoors and doesn\u2019t require heavy-duty ventilation. Safety: You will be pleased to know it has an array of safety features built-in, with its computer system protecting you from leaks and malfunctions. Pros Cons \tA powerful 10 GPM flow rate which will support even the most demanding households \tOne of the most energy-efficient gas units on the market \tIt works with very high temperatures, up to 185 degrees \tIt is one of the larger units available, weighing 60 pounds \tIt isn\u2019t the easiest to install and you may require professional assistance 10. Eccotemp L10 2.6 GPM Portable Tankless Water Heater The last product on our list is by no means the least and where it stands out is this model is portable. So if you\u2019re camping or staying in a remote cabin, then this will allow you to have a nice warm shower or hot water whenever you need it. Flow Rate: It has an impressive flow rate for a portable unit, of 2.65 GPM and runs of propane which are easy to obtain. It has a useful battery ignition system that stops any overheating from occurring, adding to its safety features. Performance: You will use a 20lb propane tank and the standard gas lines to get set up and you will be able to enjoy hot water, even heating up water that is below freezing. Pros Cons \tImpressive power to heat up water that is below freezing \tWorks with a standard garden hose and propane tanks \tPerfect for camping trips or remote cabins \tIt can take a while to heat the water up and uses more propane than you would expect. Summary We hope you have found our article on the best tankless water heaters helpful and it has provided the information you need to make an informed decision. This type of water heater is a fantastic choice for those wanting on-demand hot water or those with minimal space in their property. Product Overview Put simply, a tankless water heater will provide your home with an instant and on-demand supply of hot water. This is the primary difference with traditional hot water tanks, that keep a certain amount in the tank ready to use. You may be worried about the energy usage of these on-demand systems but because they only use energy when you use the hot water, such as switching on a faucet or the shower, they are energy efficient. Research has shown that you can save up to 37% on your energy bills. Types of tankless water heater When considering a tankless water heater system, you must first consider whether it is an indoors or outdoors model. No matter which type you go for, you have two choices about which energy source they draw from, electric or gas. Electric Pros Cons \tTypically smaller than gas alternatives Are on average more affordable than a gas water heater No ventilation is required \tMany homes will require multiple electric water heaters to produce the same amount of hot water as a gas unit They can require more maintenance Pros Cons \tMore powerful units that are able to power more than one faucet at the same time They are able to heat water that enters the system at a lower temperature Gas is often provided at a cheaper rate than electricity \tThey are more expensive than the alternative electric heater Many will require ventilation to be used safely Important issues to consider Making the decision to purchase a tankless water heater isn\u2019t a simple one and there are some important questions to ask yourself, prior to making your purchase. Capacity There are many tankless water heaters to choose from and you need to understand the capacity you require and find one that fits your needs, otherwise, you will end up not having enough hot water when you need it. You will find tables of average usage for the different rooms and faucets in your home, which will help you calculate the overall flow rate required. Indoor Vs Outdoor You can purchase a tankless water heater that is fitted either indoors, or outdoors. This will depend on the space you have in your home, the potential sound they make and whether this will cause irritation. Finally, consider ventilation requirements, as the gas models will often require ventilation and that will define where you will be able to install it. Water quality The performance of a tankless water heater will be affected by the quality of your water supply, in particular the temperature and hardness. If the water is below 50 degrees then you should go for a gas-powered system. If the water is very hard, you may need additional equipment to help with softening the water. Type of energy source We've talked about this topic elsewhere in this article but it is important to consider whether you want to go for an electric tankless water heater or a gas tankless water heater. Both types have an array of advantages and disadvantages so it is important to do your research and think about how each one best suits your needs. It may be that you struggle with ventilation, have a small budget or want to get the most powerful one available. All of these points will lead you to a different model on our best tankless water heater list. Frequently Asked Questions We have put together some of the most frequently asked questions in the hope that it helps you with your research on tankless water heaters. We are always adding more information and guidance to our reviews so if you have any other questions then please get in touch and contact us today. How does a tankless water heater work? A tankless water heater works by using a heating element to heat up cold water which enters the system. There will be a switch which is activated by the flow of the water, so that the heating element switches on whenever water is drawn from one of the faucets in the household. At this point the water flows through loops and twists in the tankless hot water heater, gradually bringing the cold water up to the right temperature of hot water. Only at this point does the water continue to flow along the water line to the faucet or fixture in question. How do you flush a tankless water heater? Each tankless water heater will differ slightly in the way you maintain and flush it, but they will normally follow the same pattern. Firstly, you should switch off the energy source, whether this is electricity or gas, as well as the water leading up to the heater. After this has been completed, connect a hose to the cold isolation valve which should be attached to a pump. Put another hose to the hot water isolation valve and leave this one unattached at the other end. Place the pump into a bucket containing approximately 4 gallons of clean white vinegar and place the pipe leading to the hotel water isolation valve into the same bucket (we would recommend a 5-gallon bucket for this job). Open both of the isolation valves and then switch the pump on. It will start to move the vinegar around the system and you should let it do this for around an hour, after which you turn the pump off and empty the bucket. Once you have finished this phase of the flush, you turn the cold water on and let the water flush out any remaining vinegar for approximately 5 minutes. After this, turn all the valves off, disconnect the hoses and return it to its original state by switching on the water and power. What size do I need? There are some key considerations to think about before knowing the size of the tankless hot water heater you require. These include the number of occupants living in the household, if there is a single point of use or more than one faucet, how many gallons per minute you need compared to what the tank delivers and finally the average temperature in your location. As you can see, we've quickly listed quite a few complex points but important points and as a general point of reference, if you have a household with 2-3 people, then hot water heaters with an output of 3 to 5 GPM is a good choice. Households with more than this number are advised to consider tankless heaters that can cope with 8GPM or more. Is electricity or gas better? There is not a specific answer here which is the same for every customer. It is all about what your individual household requirements are. For example, electric tankless water heaters are often smaller, more affordable to buy and won't require any ventilation. On the other hand, a gas unit will likely be more powerful, work at lower temperatures and energy costs for gas are often lower than electricity. As you can see, that opens up a range of further questions and key considerations for you, so our best advice is to read our full review on the best tankless water heater systems.