AO Smith vs Navien Tankless Water Heater – Ultimate Guide

Tankless water heaters are the water heaters of the future. Choosing the right one may seem like a whirlwind, especially if you’re trying to decide between two top-of-the-line models like AO Smith and Navien.

AO Smith tankless water heaters can deliver hotter water faster and are cheaper to purchase and install than Navien units. However, AO Smith units are slightly less energy-efficient than Navien water heaters and don’t last as long.

In this article, I’ll draw a detailed comparison between these two models based on energy efficiency, heating power, lifespan, and other key factors that are paramount when choosing a water heater. If you want to find out which brand performs better in various categories, read on.

tankless water heater

AO Smith vs Navien: Which Is More Energy Efficient?

The first thing you probably think of when purchasing a water heater is how it’ll affect your home’s energy efficiency. Whether you’re worried about your carbon footprint or your wallet, efficiency is crucial when it comes to water heaters. 

A Uniform Energy Factor (UEF) is a numeric measurement of a water heater’s energy efficiency. It’s based on how much energy a water heater uses when working and how much energy is needed to power it. The higher the UEF, the more energy-efficient a water heater is. 

Using the Uniform Energy Factor as a measurement of energy efficiency, the Navien tankless water heater has a higher UEF of 0.96, making it more energy-efficient than the AO Smith unit, which has a UEF of 0.92.

However, the efficiency of the Navien comes at the cost of its heating power, which we’ll look at in more detail in the next section. 

AO Smith vs Navien: Which Has More Heating Power?

The second most important factor when choosing a water heater is its heating capabilities. Most people don’t like waiting for their water to heat up or—worse still—if their water doesn’t reach a very hot temperature.

The British thermal unit (BTU) is a numeric measure of the energy it takes to raise one pound (0.46 kilograms) of water by 1°F (0.56°C). It determines how quickly you can heat your water and how hot it can get. The higher a heater’s BTU, the more powerful the heater is.

When it comes to heating power, this is where AO Smith tankless water heaters outperform the Navien product line. AO Smith tankless water heaters heat water faster and to a higher temperature than the Navien product line. 

The AO Smith water heater’s superior heating power is evidenced by the fact that it can deliver up to 190,000 BTU, while Navien water heaters only have 150,000 BTU.

So while Navien water heaters may be more energy-efficient, saving you a few dollars on your monthly electric or gas bill, the caveat is that they have less water heating capabilities and speeds than their AO Smith counterparts.

Navien tankless water heater

Which Costs Less To Operate Between AO Smith and Navien?

Navien tankless water heaters cost less to operate than the AO Smith tankless water heaters because they’re more energy-efficient. However, AO Smith units are cheaper to buy and install compared to the Navien product.

Let’s examine the cost of operation, unit price, and installation cost of each of these brands more closely. 

Cost of Operation

When it comes to the cost of operation of these units, the size of your family starts to factor in. If you have a large family, you may want a more energy-efficient heater to save money on your monthly gas or electric bill.

Operation costs are determined mainly by the gallons per minute (GPM) rather than the UEF and BTU measurements. The GPM of a tankless water heater refers to the quantity of water it can heat per minute. Generally, a higher GPM unit costs more because it can heat more water per minute than a lower GPM unit.

Both Navien and AO Smith offer different models with specifications ranging from 2 to 12 GPM, so you can choose which is best for your home. However, Navien may have a slight edge here in cost of operation because of its advantage in energy efficiency. 

Unit Price

You may save on your energy costs in the future by purchasing a Navien tankless water heater unit. However, you’ll initially pay more for the unit—a considerable amount more than the AO Smith line of water heaters.

Installation Costs

Installation costs for tankless water heaters depend less on the brand and more on factors such as the quality of your home’s plumbing and whether your unit is gas or electric. Installation of a Navien tankless water heater can cost anywhere from 575$ to 1500$, depending on whether the unit needs to be vented, if a new gas line needs to be run to the unit, and the overall condition of your home’s plumbing.

Much of the same can be said about the AO Smith tankless water heaters regarding factors affecting installation cost. However, installation, like the cost of the unit itself, does seem to be more cost-effective than the Navien units.

AO Smith vs Navien: Availability

AO Smith tankless water heaters are only sold at Lowe’s, while Navien water heaters are available from many different retailers, including Home Depot. 

However, neither model is available for purchase on Amazon.

Which Has a Longer Lifespan: AO Smith or Navien?

Warranties are a good marker of how long a manufacturer expects their product to last before becoming defective. The AO Smith tankless water heaters come with a six to twelve-year warranty, meaning that the manufacturers fully expect the units to last a decade or longer.

While AO Smith offers a six to twelve-year warranty and claims some of their units can last up to 20 years, Navien tankless water heaters boast a longer lifespan of over 20 years.

Therefore, Navien has a leg-up on longevity and reliability, which makes sense considering that their product has a higher price tag than the AO Smith tankless water heater. 

tankless water heater with switch

Final Thoughts: The Verdict

AO Smith tankless water heaters have lower purchase and installation costs, and they heat water faster. However, they fall short in terms of energy efficiency and lifespan.

The Navien costs more on the front end but saves you money later on, thanks to its higher energy efficiency. Navien units have less heating power, but that’s because they’re more energy-efficient. 

If you have the money, go with the Navien. Your water may not reach scorching temperatures instantaneously, but your energy bill will be lower. Also, Navien has about double the lifespan of AO Smith, and that seals it for me.