Eccotemp FVI-12-LP (Propane) or FVI-12-NG (Natural Gas) Tankless Water Heater Review

A versatile high capacity propane tankless water heater from the Eccotemp line that comes with a low price tag.

Many people switch to tankless water heaters to live a greener, more eco-friendly life, the kind that can't be enjoyed with bulky energy-guzzling water tank heaters. 

But which brands truly represent a step in the right direction?

Which units will save energy and improve sustainability while also delivering the hot water you need as a modern homeowner?

Let's talk about the Eccotemp FVI-12-LP High Capacity Propane Tankless Water Heater and its Natural Gas twin brother, the Eccotemp FVI-12-NG. 


The first thing you should know is that the FVI-12-LP (NG) is a small, compact unit that doesn't require a lot of space. It's only 4 x 15 x 24" and 20 pounds!

You can install this water heater absolutely anywhere in your home, including under sinks and inside supply closets.

As for power, while it doesn't generate the energy that bigger units do, its low demands come with a silver lining. For example, while it only offers 100 volts, it only requires 74,500 BTUs.

According to Eccotemp, you can save up to 50 percent on your energy bill every month just by switching to the FVI-12-LP.

Last but not least, the maximum flow rate of the FVI-12-LP (NG) is 4.8 gallons per minute (GPM).

This is enough for 1-2 bathrooms with multiple demands on sinks, showers and appliances. If you like to run the dishwasher or do a load of laundry during your baths, this unit will accommodate you.


The FVI-12-LP runs on liquid propane and the FVI-12-NG, on Natural Gas, so if you aren't familiar with propane and natural gas tankless water heaters, here's a basic rundown of their operation:

1. Internal sensors detect cold water rushing through the pipes.
2. Live burners turn on and warm up the heat exchangers.
3. Cold water circles the heat exchangers until it's heated to the right degree.

Since a live flame is involved, you'll need to install a venting system for the fumes, but the good news is that Eccotemp includes stainless steel vents with your order.

We'll talk about that more in the installation section.

As for everyday functionality, you won't have a problem using the FVI-12-LP (NG).

There's a digital interface on the box where you can adjust the temperature to your exact specifications, and there are even separate knobs for gas and water.

This isn't a fancy model where just touching it requires an extended how-to guide.

You can figure out the FVI-12-LP (NG) by simply looking at it.

Heat Output and Flow

As previously mentioned, the flow rate of this unit is 4.8 GPM, and that's enough to service either multiple bathrooms or a kitchen and bathroom at the same time. Please note, however, that the FVI-12-LP (NG) isn't designed for large homes.

It's a small unit meant to be used in smaller contexts. 

If you have excessive hot water demands, you may need to install more than one FVI-12-LP (NG) on your property or a single, higher capacity unit. 

Temperature-wise, the FVI-12-LP (NG) will deliver exactly what you need and when you need it.

There are very few flow delays reported with this product, so your temperature and water pressure are all but guaranteed.

Another great thing about the FVI-12-LP (NG) is that it only uses energy when it's actually turned on.

It isn't a so-called "energy vampire" that runs up your utility bill when you least expect it. The FVI-12-LP (NG) stays silent until it's actively running, and even then, it uses much less energy than other water heating systems.


While the FVI-12-LP (NG) isn't excessively difficult to install, care should be taken since it's a liquid propane unit that will produce fumes while in use. You might want to let a certified Eccotemp technician do the installation for you just to be safe.

If you do want to tackle it yourself, however, here are a few of the things you might need to get the job done:

  • Regulator
  • Circuit breakers
  • Ground lines
  • Copper wiring

A stainless steel venting system is included with your order, so you won't have to worry about that. You can also buy add-ons and extras if you want more customization options.

General Use

Every product has an Achilles heel. Before purchasing any tankless water heater, including the FVI-12-LP (NG), you should take a good look at the pros and cons.


  • Small, compact unit that can be installed anywhere
  • Extremely energy-efficient
  • Low price


  • Not suitable for large homes
  • Requires venting system for fumes
  • Non-lifetime warranty

What's the bottom line?

If you're looking for an excellent propane or natural gas tankless water heater, you'll definitely want to consider the FVI-12-LP (NG). Not only is it functional and affordable, but you'll be helping the environment by using it, too.

We give it a solid three and a half out of five stars in terms of overall performance. Check it out on Amazon to see its reviews for yourself!

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