Product Review

Rheem rte 9: Hot Water System Reviews

by Matt Moran

Are you looking for an efficient, low cost water heater but running low on space? An alternative to the traditional tank-based water heater is the tankless water heater. While significantly smaller than their tank-based counterparts -- weighing only eight pounds -- tankless water heaters can still provide hot water on demand.

Their small size also makes them significantly more versatile; they fit almost anywhere. Tankless water heater manufacturers also claim tankless models are far more efficient than their tank-based counterparts.

The Rheem RTE 9 Tankless Water Heater, 3 GPM is one such tankless water heater. In this article, I will look at the pros and cons of the Rheem rte 9 review. The article will conclude with a recommendation to let you know if the Rheem RTE 9 is the right water heater for you.

Rheem RTE 9 Features

It’s All Electric

One of the greatest benefits of the Rheem RTE 9 is that it’s all electric. While it may raise your electric bill a bit,it won’t use any gas. Some users mention the large savings on their gas bill. Some also mention feeling an added degree of safety not using combustible natural gas.

The Rheem RTE provides continuous heating, provided on demand. The unit switches on only when water is passing through it. When not in use, the Rheem doesn’t use any electricity, saving customers even further.

The Rheem RTE 9 is Small

The Rheem RTE 9 is much smaller than a traditional tank-based water heater.Traditional water heaters heat 40 or 50 gallons of water in a large storage tank. The Rheem RTE 9 weighs about eight pounds and is 10” by 8” -- about the size of a picnic basket.

This means you can put it in places you simply can’t put other heaters. The Rheem fits neatly in closets or crawl spaces, though it does require a 40 amp breaker and copper wiring.

Continuous Hot Water on Demand

Rheem claims a temperature rise of up to 35 degrees for the Rheem RTE 9. This is at a flow of 2.2 gallons per minute. At lower flow rates, the temperature can be regulated even higher. All users need do is run the water -- the unit turns on and heats outgoing water automatically.

The RTE 9 is ideal for small applications such as kitchen sinks, vanities, restricted flow shower heads, and washers. For applications requiring more water or with colder inflows, a larger unit may be required.

Easy to Install

Many users were able to install the RTE 9 on their own. There's no need to open the unit for installation. In fact, all that is required is a 40 amp breaker with 8-gauge copper wiring, then attaching brass intake and outflow fittings to existing plumbing. If a plumber does the installation, it’s a quick, inexpensive job. Licensed technicians doing the installation keeps the warranty valid.


Rheem offers a 1 year warranty on all component parts of the RTE 9. Keep in mind the warranty is only good if a licensed technician installs the unit. The heat exchange is warranted for ten years. Many users mentioned Rheem’s friendly customer service. In the unlikely event something goes wrong, Rheem will be quick to fix it.


  • Temperature control
  • 1/2” water connections
  • Unit turns on/off automatically
  • High efficiency
  • Easy to install
  • Low-flow activation


  • Can only raise water temperature about 35 degrees
  • Not applicable for high flow applications
  • Warranty valid only if installed by licensed technician
  • Requires a bit of rewiring and a 40 amp

Highlighted Features

  • Continuous hot water on demand
  • Increases temperature of inflow by 35 degrees at 2.2 gpm
  • Small, compact unit; can be used anywhere hot water is needed
  • All electric heater

Frequently Asked Questions

By how much does the RTE 9 increase water temperature?

This depends on the flow rate.

  • At 3 gpm, the increase will be about 20 deg F;
  • At 2.05 gpm, the increase is 30 degrees;
  • At 1.54 gpm, the increase is 40 degrees;
  • At 1.23 gpm, the increase is 50 degrees;
  • At 1.02 gpm, the increase is 60 degrees;
  • At 0.88 gpm, the increase is 70 degrees;
  • At 0.77 gpm, the increase is 80 degrees;
  • At 0.68 gpm, the increase is 90 degrees;
  • At 0.61 gpm, the increase is 100 degrees.
Does the Rte-9 use 120 or 240 volts?

It uses 240 volts with a 40 amp breaker and 8-gauge copper wiring.

Final Verdict

The Rheem RTE 9 is an all-electric, compact alternative to a tank-based water heater. It works well for applications that have an inflow of 55 degrees or higher and an outflow of 2.2 gallons per minute or less.

In this case, it would work best with small scale applications like sinks, restricted flow shower heads, or washers. If this sounds like what you need in a low cost water heater, consider looking closely at the Rheem RTE 9, it may be the perfect heater for you!

Matt is a freelance writer, English graduate, & keen traveler from the UK. As a specialist plumbing expert, he enjoys writing about everything there has to do with at-home plumbing products & related problems. When he isn’t writing, he’s usually drinking coffee or planning his next adventure. In his spare time, he also runs his own blog all about digital nomad life.