The Clear Path to Net Zero Energy.

Save Energy with the Sanden SANCO2™ Hot Water Heat Pump System

  • 5x more efficient than traditional electric water heater

  • Allows use of off-peak power

  • Greater first hour rating than all heat pump water heaters

  • Faster recovery after hot water draw

  • Hot water production down to -20°F & below

  • Up to 175°F delivered hot water temperature

Efficient Operation: How the Sanden SANCO2 System Works

The Sanden SANCO2™ Heat Pump Water Heater is a two-part system consisting of a tank (usually placed indoors) and a heat pump unit (usually placed outdoors, up to 50 ft away from the tank). The heat pump works like a reverse air-conditioner, drawing heat energy from the atmosphere and applying it to water from the tank. This technology is already in wide use in industrial applications as well as residential water heaters in countries like Japan and Australia. 


The Sanden SANCO2 works just like a conventional heat pump, except that it uses CO2 as a refrigerant. Due to the unique properties of CO2, the Sanden operates very efficiently in a wide range of temperatures. It is able to extract heat from the air all the way down to -20°F  and beyond in a single heating stage, raising the water temp as high as 175°F at .3 gallons/minute. The result is a system that requires radically less electricity to heat water when compared to conventional hot water systems and works without a backup coil in a very wide range of climates.

While the Sanden system is a perfect choice to replace an existing gas or electric hot water tank in any residential or multifamily application, the ability to work at low exterior temperatures and still supply hot water at 175°F means the same system can be the total solution for today's new low energy homes.

The Sanden SANCO2 Uses CO2 As a Refrigerant which is Ozone Friendly & Doesn’t Contribute to Global Warming

A heat pump uses a small amount of energy to move heat from one location to another. In the SANCO2 system heat in the air is absorbed by a natural refrigerant, CO2, which is ozone friendly and does not contribute to global warming.

The warm gaseous refrigerant is circulated in the system via a compressor. As it passes through the compressor, its pressure rises, as does its temperature. This hot refrigerant then passes through a heat exchanger to heat the water, which is then pumped to the storage tank.


The Combi-System : DHW plus Space Conditioning

With a capacity to deliver 15,000 btu/hr, A Sanden SANCO2 heat pump hot water heater can be designed into a system that delivers all of the domestic hot water (DHW) as well as heated water for space conditioning. This is accomplished with one circuit feeding a DHW mixing valve to reduce the temps to 120°F, and another supplying a standard heat exchanger supplying hot water radiators, radiant slab, or forced air fan coils.

For homes with a design temp of 12°F or higher, and a heat load of 8kbtu/hr or less, this can be the entire DHW and space conditioning system. Additional on demand hot water heater systems can be added into a design for homes with larger heat loads or used back up systems to provide added capacity for extreme weather events or large homes where all but the coldest days can be supplied by the default Sanden system. It's important to note that this COMBI technology is still in the development phase. As features are improved and more projects report success, the 8kbtu heat load can be increased, and lower design temps added, based on capacity improvements and project results.  

Multifamily DHW Projects and the New 119-gallon Tank

The efficiency of the SANCO2 is attractive for new multifamily projects but the offering of 43 and 83-gallon tanks are tough to fit into a building since space is tight.  With a new 119-gallon tank things change. At the typical 149F water temperature, the 119-gallon tank can deliver about 158 gallons of 125F water. However, as you look deeper at the new G3 heat pump options you find the output temperature range is variable from 130F to 175F. By increasing the heat pump output temperature to its 175F maximum, the tank now is full of 175F water. The yield of the tank at 175F increases from 158 to 198 gallons. Now a single tank can serve 4-5 apartments. This approach significantly reduces cost and space required in multifamily building applications. It’s the new clean and efficient way to make the most of the new G3 heat pump and a tank that holds 36 extra gallons. By placing the buildings DHW system into smaller distributed plants serving nearby units, the internal heat gains resulting from long DHW recirculation runs are reduced resulting in less need for cooling and also getting the full use of the high COP from the CO2 refrigerant heat pump.  

It’s a bit astounding that a 30% increase in tank volume and the ability to increase the output temperature of the heat pump will yield a 66% increase in delivered DHW.  The DHW tank yield is calculated using three variables:  1) Heat pump output temperature, 2) Incoming water temperature from the cold water supply, 3) Mixing valve set temperature to the building occupants. Sanden has created a mixed water fraction chart covering all of the variables which can be used to calculate the DHW yield for any project. You can download the document here.

Ten years of CO2 Heat Pump Success and Counting...

While heat pumps using CO2 as a refrigerant are new to us, Sanden has been producing these systems in their original market of Japan for close to a decade. The culture of Japan still enjoys bathing in a hot water bath as a relaxing and healing experience. As the ability of the Sanden CO2 heat pump became known to efficiently deliver a high volume of very hot water, Japan embraced and developed the technology as the preferred method to supply the large amounts of hot water for a "bathing culture".

Success in Japan brought success to the rest of the world with the movement of the majority of European and Asian vending machines and other refrigeration units moving quickly to CO2 heat pumps as the "new way to lower  operating costs".

These systems are in stock and available for next day shipment in both our Tumwater, WA and Vancouver BC locations

Sanden Frequently Asked Questions

+ What makes a Sanden Heat Pump Water Heater different from other water heaters?

Traditional water heaters use inefficient heating elements (electric resistance) burn fossil fuels (Natural gas/propane) or use high global warming potential refrigerant gases (traditional heat pump water heaters) to produce hot water. The Sanden HPWH uses CO2 as its refrigerant, which allows it to achieve 30-40% greater efficiency and work in a wider temperature range than even the most efficient traditional heat pump water heaters.

+ What is the operational temperature range?

The Sanden HPWH works in temperatures from -20F to 110F

+ When will I make my money back?

Based on an average $0.124/kwh we estimate you will see a return on investment, depending on usage and climate, within 5 years.

+ Are there any rebates available?

Most utility companies in the Pacific Northwest have rebates available, and you can search by zip code at For further information, please contact your local utility provider.

+ What unit sizes are available?

The outdoor unit comes in one size, but feeds a varying size tank. We have43-gallon, 83-gallon, and 119-gallon hot water tanks available.

+ How much hot water can this unit deliver?

The 43 Gallon tanks have a 1st hour hot water delivery rating of 71 gallons, while the 83 gallon tanks deliver 101 gallons in the first hour. The 119 gallon tanks deliver 158 gallons of hot water in the first hour.

+ What is the hot water recovery rate?

The Sanden heat pump is able to produce 16 to 23 GPH of 131- to 176-degree Fahrenheit water (depending on heat pump settings).

+ How many BTUs?

The heat pump delivers 15,400 BTU/hr.

+ What are the dimensions for the heat pump and tank?

Please refer to the Sanden specifications sheet and be mindful of the hot water tank model numbers.

+ What are the electrical installation requirements for the Sanden?

The heat pump requires a dedicated 15a 208/230v – 1Ph – 60Hz connection. The tank is non-powered. Please refer to the installation manual for further information.

+ What is the coefficient of performance (COP) for the Sanden system?

The COP will differ depending on the outdoor temperature and temperature of the incoming cold water to the heat pump. You will see higher efficiencies with warmer weather and colder incoming water.

+ How do we protect the water lines from freezing?

Insulation on the outdoor water lines is required, and a heat trace kit is recommended.

+ Can the Sanden be used as a combination domestic hot water and radiant heating system (Combi)?

Certainly. Your heat load must be less than 8,000btu/hr with a design temperature of 12F above, and Sanden recommends you use at least 20 Gal of domestic hot water per day to maintain tank stratification and efficiency.

+ What are the requirements/limitations in a combination setup?

The requirements and limitations are as follows:

Sanden HPWHs are not designed for use in heating-only applications. They must be used as ONLY domestic hot water heaters or combination DHW and heating. Sanden recommends using at least 20 gal of domestic hot water per day maintain hot/cold stratification in the tank. This stratification is required to achieve high COP.

The Sanden combination system using a single heat pump is not designed to heat spaces requiring more than 8000 btu/hr (around 2500w).

In cases where there is additional load being met by backup or additional heat sources, the system can employ DHW priority through the Taco X Block. This feature will maintain the DHW temperature during periods when the Sanden cannot keep up with the heating demand.

Additionally, two heat pumps can service one 119gallon tank in a combi-system. This can increase the capacity for heat load to 16,000btu/hr.

Sanden requires that the domestic hot water and space heating loops be separated by a heat exchanger, specifically the Taco X Pump Block. A heat source protection sensor is also required to be used between the heat exchanger and the hot water tank.

We are currently working on developing our network of recommended installers for the Pacific Northwest. Fortunately, the Sanden has very simple installation requirements and can be done by any licensed plumber.

+ Are the Sanden Systems approved?

The Sanden systems have both UL and CSA Certification

Shop Sanden heat pumps and accessories at our Small Planet Supply online store. Click the icon for your country to shop Sanden products:

New Sanden installation video for simple residential applications.

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Sanden - Down Under

Three videos from market development work in Australia: Introducing the concept, saving money, environmental impact of a heat pump using CO2 as the refrigerant.

As a HVAC service person, these units hands down out perform any other heat pump water heater and the warranty was another reason to buy also. Highly recommended.”