Rinnai RU90eN Ultra Series Outdoor Water Heater Review

Product Name:RU90eN Ultra Series 9 gpm Outdoor Natural Gas Tankless Water Heater
Power Source:Natural Gas
Use Type:Ourdoor
Capacity:9.0 GPM
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The Quick Review

If efficiency and long term savings if what you’re after, then look no further than the Rinnai RU90eN Ultra Series 9 GPM Outdoor Natural Gas Tankless Water Heater. With the absolute industry leading 96% effiency on an outdoor unit, which is the best you’ll find, bar none. In addition to being built by Rinnai, one of the leaders in water heaters, it is backed by a 10 year warranty on the heat exchanger which sets the standard for all other outdoor tankless water heaters.


With an industry leading 9.0 GPM flow rate, you will be able to heat up to 3 outputs at once. For example, you could heat two showers and a diswasher at the same time, or a washing machine, a dishwasher, a shower and a kitchen sink. That is basically all the hot water the average home would need.


Since this tankless water heater requires a gas line hook up, you will require professional installation. We do not recommend an amateur attempt to install this unit as working with gas lines can be very dangerous. That said, for a professional, this installation is quite straight forward and shouldn’t run up a large labor bill. Many individuals on Amazon has reported that they were able to install it themselves with ease.


Being 96% efficient, the Rinnai RU90eN represents the best long term value, in terms of energy savings over time. The majority of outdoor tankless heaters are between 80%-90% efficient, so you’ll be saving nearly 6% more per year using this unit. That is why it is slightly more expensive.

Over the long run, the extreme efficiency of this unit using natural gas will be much less expensive than electric hot water tanks.

The Misses

Most tankless water heaters take a while for the water to heat up when you turn on the faucets, and this unit is no exception. It can take up to 15 seconds (in the winter) for the water to heat up, which is slower than conventional electric water tanks. For a unit of this quality, we would expect them to innovate in this area.

Our Recommendation

We definitely recommend this product for any house with up to 2 bathrooms and large appliances. Be sure to check the price to see if a discount is available today.

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