3-in-1 energy recovery device

The 3-in-1 Energy Recovery Device (ERD) optimized for sea water reverse osmosis applications. With iSave you get pressure exchanger, booster pump and motor integrated into one compact unit for high efficiency and short pay-back time.

The small footprint of iSave makes it a popular solution when the space is limited. When fitted with iSave, the Danfoss APP pumps produce more fresh water per square meter than any other system in the market.

iSave can be used in almost any SWRO application – land-based or marine, new or retrofit. The 3-in-1 design allows fast commissioning, continuous monitoring of performance and easy regulation to accommodate seasonal changes. Other isobaric devices have been known to cause over-spin and over-flushing that lead to poor process control and low efficiency. This is avoided with the active control possibilities offered by the iSave technology.

iSave captures hydraulic energy from the high pressure reject stream of the SWRO process and transfers the energy back into the system, drastically reducing the energy consumption regardless of flow rate and size of your SWRO system. Besides substantial energy savings, the iSave ERD also cuts capital expenditure by reducing high-pressure pump size, number of pipes and components thanks to its integrated design.

iSave ERD for reverse osmosis - Brochure - Danfoss

Superior energy recovery in SWRO

Danfoss iSave is a patented, high-efficiency Energy Recovery Device (ERD) that guarantees constant membrane feed in SWRO applications of any size – on land, at sea or on the move.

Features and benefits

Extensive application know-how

Competitive efficiency rates

Compact – pressure exchanger, pump and motor in one unit

Easy and service-friendly design

Simple and reliable with high uptime

Short pay-back time

iSave selection tool - Danfoss

iSave selection tool

Download the iSave selection tool for easy calculation and selection. Calculate amount and size of iSaves for your project.

Meet Jan from Danfoss HPP

Meet Jan - our service manager

He gets to travel to exotic locations all around the world and help our customers set up and use our solutions and technology.

Wherever simplicity and space matter, iSave's 3-in-1 design makes energy recovery as easy as it is efficient.

iSave's unique design puts three key components of isobaric energy recovery exactly where they belong: right next to each other. So now engineers can configure RO systems that are simpler, smaller and easier to operate – not least in tight places like containers.

When installed with compact APP high-pressure pumps, the Danfoss pump-and-ERD package produces more fresh water per square meter than any other system on the market.

The importance of energy efficiency in the desalination process

Juan Manuel Ortega, renowned desalination expert, tells about the importance of using highly efficient energy recovery devices and high-pressure pumps.

Highly energy efficient high-pressure pumps

With efficiency rates up to 92%, the APP pump technology offers the highest efficiency in the industry.

Product range

  • iSave 21 Plus energy recovery device (ERD) for reverse osmosis applications
    iSave 21 Plus

    iSave 21 Plus is a powerful ERD for smaller plants with a water capacity of 110 to 350 m3 per day. iSave 21 Plus is designed for high reliability, low maintenance and reduced lifecycle costs.

  • iSave 40 energy recovery device - Danfoss
    iSave 40

    The iSave 40 consists of an isobaric pressure exchanger, a high-pressure positive displacement booster pump and an electric motor. Max. differential pressure: 5 barg/72 psig. Speed: 600 - 1200 rpm.

  • iSave 50 energy recovery device - Danfoss
    iSave 50

    iSave 50 is designed for use with low viscosity and corrosive fluid such as sea water. Max. differential pressure: 5 barg/ 72 psig. Speed: 525-650 rpm

  • iSave 70 energy recovery devices - Danfoss
    iSave 70

    iSave 70 is designed for use with low viscosity and corrosive fluid such as sea water. Max. differential pressure: 5 barg/ 72 psig. Speed: 625-875 rpm.


Type Name Language Valid for Updated Download File type
Data sheet iSave 50 -70 Data sheet English Multiple 31 Mar, 2018 2.2 MB .pdf
Brochure Superior energy recovery in SWRO English Multiple 18 Jan, 2018 1.2 MB .pdf
Brochure Superior energy recovery in SWRO Spanish, Castilian Multiple 17 May, 2018 1.2 MB .pdf

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Case studies

  • Suez chooses oil-free Danfoss APP pump to power Bahamian RO plant retrofit

    For a resort in Bahamas APP pump and iSave ERD were selected to supply fresh water. Both components are well-known for long service intervals, high reliability and energy efficiency. They eliminate risk of oil contamination on the plant site, as they use the pumped medium for lubrication.

  • Seawater
    Creating a sustainable future with seawater

    Over the past decade, the use of Sea Water Reverse Osmosis (SWRO) for desalination has taken off. With proven efficiency rates up to 92% and energy savings of up to 65% compared to traditional solutions, the opportunities of SWRO technologies deserve further exploration.

  • Next generation iSave 21 plus
    Next generation iSave 21 plus

    Danfoss launches a new generation of the popular iSave 21 ERD for smaller SWRO plants. Improved reliability, design flexibility and high efficiency are some of the features of the new iSave 21 Plus.

  • The buried treasure of Jeju Island transformed into fresh water Danfoss
    The buried treasure of Jeju Island transformed into fresh water

    Krosys is a leading Korean firm with long experience in SWRO systems. Krosys had no doubt that the APP pumps from Danfoss would be the most energy efficient way to transform the "lava water" into fresh Water at the Korean Jeju Island.

  • Solar Power Danfoss
    Danfoss at the heart of new ultra-efficient RO plant that uses nothing but solar power without battery backup

    Mascara NT chose Danfoss pumps and ERDs to drive an RO plant whose only energy source is the sun. Specially developed for some of the world’s most arid and isolated regions, the new OSMOSUN system is designed to produce water so efficiently that it does not need energy storage. By eliminating costly battery packs, Mascara NT’s solar powered plant radically reduces total life cycle costs and enables clean water in locations completely off the grid.

  • SWRO Units Danfoss
    Danfoss iSave® ERDs at the heart of new, high-end containerized SWRO units

    Get to market fast with a containerized, low-maintenance high-performance SWRO plant. Pre-engineer it to be flexible enough to accommodate a wide variety of desalination conditions. And deliver at a good price.