Smart Cylinder™

Endless hot water, when you need it

Efficient electric water heating

A hot water cylinder that typically saves up to 10% on your water heating bill!

What is it?
The way that a traditional electric hot water cylinder works means that you are paying to heat all of the water in your cylinder 24 hours a day, 7 days a week, 52 weeks of the year. The Rinnai Smart Cylinder™ has a smart thermostat which learns the pattern of hot water use, and then only heats the water when it knows it's going to be needed.

 It's easy to use too with an LCD control pad, simply set and forget.

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Product Details

Suitable for residential indoor water heating applications—mains and low pressure systems. A Smart cylinder is ideal for households that have a regular pattern of hot water use, as consistency is key. Also there is some interaction needed with the Smart controller, which is mounted on the cylinder. Easy access to the cylinder and controller is important. Smart Cylinders are not suitable as a pool or spa heater, or for connection to an open loop solar or hot water heat pump system.

Water quality

Rinnai cylinders are made to suit most NZ council water supplies. However some water supplies can have a detrimental effect on the cylinder, its operation and life expectancy. Stainless steel cylinders ARE NOT suitable for bore or tank water. Water supplies with a high level of calcium carbonate (hard water) can cause scaling on hot surfaces. We recommend a water temperature of no more than 65 ºC to minimise scale build-up. Scale reducing or water softening devices should be considered in hard water areas. The cylinder is not guaranteed against damage due to scaling.

Technical Specifications

Energy cost saving references

1. The savings claim is verified by results from European tapping tests.

2. The European efficiency testing standard for a hot water system uses 'tappings'. Tappings are calls for hot water from the cylinder at various times to simulate real life hot water use.
3. Actual savings made will depend on the installation although savings of up to 10% are typical. 5.Savings are influenced by a number of factors including cylinder size, hot water use profile and plumbing system design. Savings are made by the reduction of heat loss from the cylinder and all of the associated components in the plumbing, including the pipework.


Hot and cold water connections ¾ " (20 mm)

Factory preset temperature 

55 °C  

Model code and REU number 

850 kPa (MP enamel, and SS cylinders)
120 kPa (low-medium pressure stainless steel)

Hot water capacity 

26 L/min (1560 L/h) at a 25 °C rise  

Exhaust system 

Cotherm iQuaflex 14 A probe thermostat

Frost protection 

Rating of TPR supplied with cylinder— factory set to 850 kPa and 90 °C.

Ignition system

Based on a thermostat temp. setting of 60 °C and an incoming water temp. of 15 °C

• 135 L = 2 hrs 37 mins (3 kW)
• 180 L = 3 hrs 30 mins (3 kW)
• 250 L = 4 hrs 51 mins (3 kW)


How does Rinnai calculate their claim of typical hot water heating savings of up to 10%?

Savings are influenced by a number of factors including cylinder size, hot water use profiles and plumbing system design. Savings of up to 10% have been observed. The savings claim is verified by results from European tapping tests. The European efficiency testing standard for a hot water system uses “tapping’s”. Tapping's are calls for hot water from the cylinder at various times to simulate real life hot water use.

Can I put a Smart controller on to an existing cylinder?

We would love to be able to put Smart control on every hot water cylinder in NZ, but due to electrical compliance requirements we can only supply these as part of a complete unit – the Rinnai Smart Cylinder™. There are also complexities with selling the Smart controller as a standalone item, as the control is developed specifically for each size hot water cylinder, to ensure maximum efficiency as well as for safety reasons.

How long does it take to learn a new pattern?

The system spends the first week learning a pattern, then by the end of the second week it starts to apply savings. As patterns change, this is gradually integrated into the savings algorithm and the Smart Cylinder updates its heating pattern on an ongoing basis.

What is the warranty on the Rinnai Smart Cylinder™?

The cylinder is covered under the warranty for the cylinder type, e.g. Stainless Steel has a 10 year warranty, while the Mains Pressure Enamel range has a 7 year warranty. The Smart controller as a component has a warranty period of 1 year from the date of installation.

How does the Rinnai Smart Cylinder™ reduce the risk of legionella?

The Rinnai Smart Cylinder™ has an anti-legionella feature built in which meets the requirements of the New Zealand Building Code₁. To disinfect water for legionella bacteria, the system will perform heating above 60 °C whenever risk conditions are detected. ₁Clause G12.3.9

Is it possible to supply the cylinder with LED control pad locatable away from the cylinder?

The control pad for the Rinnai Smart Cylinder™ is connected to the thermostat in the cylinder via a cable. Due to electrical compliance requirements, mounting the control pad on the cylinder is currently the only option. Like any product, there will be continuous improvement over time and eventually there may be the option to have a wireless controller or the technology to control the unit via mobile phone. The current design is a huge step forward in the efficiency of the electric hot water cylinder market in NZ. The great thing about the Rinnai Smart Cylinder™ is that it works very well with not much input from you, the homeowner. The control is a set and forget product which allows you to make savings without having to do anything, it isn’t a control that you need to check or adjust. When the cylinder is installed, the level is set on the control pad (most people choose level three, the default setting) and then the cylinder begins to learn your habits and make savings. There may be the odd instance when you may want to change the mode - for example if you are going on holiday or have guests staying and your hot water pattern changes.

Will you be developing an app that will enable remote access to change the setting?

We are not currently working on this and have no timeframe by which we might start.

What if more hot water is required, i.e. additional people coming to stay?

There are a few options here: You could put the cylinder onto manual mode, which will result in it working the same way a standard electric hot water cylinder (there will be no savings during this time period) and then revert back to your preferred setting once your guests have left. Alternatively, if you still want to enjoy some savings then you can increase the level of comfort on the controller, which means that the cylinder will produce more hot water while still delivering savings.especially if you have young children, the hot water can be pre-set to a child-safe level 

  • No need to mix hot and cold water, this reduces the changes in water temperature when another tap in the building is turned on
  • You use your continuous flow unit more efficiently as less gas is required to heat water to 40 °C (typical shower temperature) than at 55 °C (which is the default temperature without controllers) 
  • Highlights any problems (disruption in gas supply etc.) by displaying error codes on the controller