The story of OSO

A Norwegian industrial adventure

OSOs adventure through 3 generations, from the start in 1932 to today.

The Family business

The founder – Reidar Frölich Braathen – started “Oslo Sveisebedrift” (OSO) in Oslo in 1932, as one of the first welding shops in Norway. Reidar was both a blacksmith and a lieutenant in the air force and among the first in the country that mastered both electric – and autogenous welding. With minimal resources he created the first welded water heater in Norway. Thanks to his continuous innovation and dedication Reidar employed 100 people by 1940. His 50 years of experience became the foundation of OSO Hotwater – a Norwegian industrial adventure.

2nd generation – Chris Reidar Braathen – was very much involved in restoring the factory after the war. In 1964 Reidar established OSO by the Drammen river, where the production of water heaters is still located today. Chris Reidar was a technician and had great commitment and drive, in addition to idealistic ideas. He has, during his 50 years in OSO, combined industry and protection of the environment in a unique way and has given OSO the recognition as one of the leading environmental enterprises in the Nordic countries.

3rd generation – Sigurd Braathen – continues to lead OSO with a clear objective to still be a family business in Norway. Dedicated to improving OSO’s products and processes, Sigurd continues to build the company brick by brick, and is proud of the fact that OSO has become one of Norway’s most robotized companies. The pioneering spirit lives on with product innovations featuring integrated solutions, ground-breaking material technology and added value for our customers.


The company has three main markets:

  • NORWAY: Thanks to continuous innovation, trust and confidence from our customers, OSO is the clear market leader in Norway over the last 85 years. Our products delivers well-being and hotwater to two-thirds of all homes in the country, with exceptional lifetime economy.
  • OEM: We are proud to be a preferred supplier to many of the best-known brands in the heating industry, delivering our products throughout Europe, Northern America and Asia. OEM is an important part of our business because it inspires and motivates us to think innovatively, be flexible in our approach and challenge traditional mind-sets.
  • EXPORT: OSO focuses on the Nordics, UK, Russia and Canada, as well as the shipping and offshore markets. Export sales make up about 40% of the turnover and gives us a unique perspective and knowledge of water qualities and product properties which benefits all our customers.

Historic milestones

A Norwegian business adventure through 3 generations:

  • 1932                     OSO is founded by Reidar Frölich Braathen by Akerselva in Oslo.
  • 1939                      100 employees has their daily work at Oslo welding company.
  • 1940                      Norway is occupied by Germany and the factory is shut down.
  • 1940-1945           The Braathen family relocates to their farm, producing agricultural equipment.
  • 1945                      Reconstruction of OSO starts after the end of the German occupation.
  • 1950                      OSO again becomes market leader of hot water heaters in Norway.
  • 1955                      The factory requires more space and relocates to Geithus.
  • 1956                      2nd generation starts in the company and takes over the daily operation.
  • 1964                      The current OSO factory is established by Drammenselven.
  • 1968                      OSO manufactures the first stainless steel water heater in Europe.
  • 1985                      Water heater no. 1 million is manufactured at OSO Hokksund.
  • 1990                      NOK 100 million in turnover.
  • 1991                      The export business is established and international sales begin.
  • 1993                      OSO Hotwater UK is established, revolutionizing the UK market.
  • 1998                      NOK 25 million is invested in knowledge and jobs in Norway.
  • 2000                      NOK 200 million in turnover.
  • 2002                      A 1,000 m2 training center is built to educate future professionals.
  • 2004                      3rd generation starts in the company, and takes over the daily operation.
  • 2005                      NOK 80 million investment.
  • 2006                      NOK 400 million in turnover.
  • 2010                      NOK 50 million investment.
  • 2014                      NOK 50 million investment.
  • 2015                      OSO is the most robotized business in Norway.
  • 2016                      Water heater no. 4 million is manufactured at OSO Hokksund.

Environmental efforts through 50 years

OSO is one of the first environmental enterprises in Norway with more than 50 years of efforts and investments to unite people, environment and industry. The environment effort started with Reidar Braathen Jr. in 1956 who created “The most environmental company in Scandinavia” (SCANVAC award). After 50 years of continuing effort for both indoor – and outdoor environments, GRIP together with the Minister of Environmental Protection, Arild Hareide, awarded the special “Glassbjørn”-award to OSO for our effort to save the environment.

Thanks to the loyalty of our customers, OSO has become a concept for both water heaters as well as environmental protection. Products with extremely long life-cycle and the lowest heat loss of any storage tanks on the market is our biggest contribution to the environment, in addition to a zero-emission production and no toxic waste released of any kind. Love and care for our nature is the basis for our engagement in protecting the environment, our objective is the same as 50 years ago: PROTECT OUR BEAUTIFUL PLANET.

Among the most important environmental efforts are:

  • 1968      Europe’s first stainless steel water heater increased the lifespan of water heaters.
  • 1980      Mixing valve increased efficiency by 30% and reduced the amount of steel needed.
  • 1990      The first “Resirc-system” in Europe for discarded storage tanks.
  • 1990      OSO establishes an annual NOK 100,000 “Bronseelgen”- environmental award.
  • 1994      OSO is among the first companies to eliminate the use of CFC gases.
  • 1994      Free bicycle to every non-smoking employee and a paid reward per kilometer.
  • 1994      All company vehicles are converted to run on natural gas reducing emissions by 30%.
  • 1995      Gives NOK 5 million to environmental purposes – establishing OSO environmental fund.
  • 2004      ECO FOAM saves more than 500 million kWh in heat loss over 10 years.
  • 2010      10 million liters of water is saved in Energy Conservation efforts during production.
  • 2015      The world’s best isolated storage tank - DELTA – is introduced.
  • 2017      NANOPUR and VACUUM panels saves 200 million kWh over 10 years.


The OSO Environmental Fund have contributed to these projects:

  • Thor Heyerdahl                               The documentary “Progress”
  • Bellona                                                The Russian Northern Fleet-campaign.
  • The Rainforest Fund                      Save the rainforest.
  • Rein Dammann                                “The call of the Wild”
  • Børge Ousland                                 “Alone across Artic” – climate research.
  • Lars Moxheim                                  The Sverdrup Expedition
  • New Paradigm Films                      Project “Free Energy”

World-class manufacturing

OSO is dedicated to manufacturing in Norway, against all odds. We’ve offset the high-cost environment with continuous automation, and are proud to be Norway’s most robotized company. Automation provides unique repeatability, and the ability to integrate 100 % process control for CTQ operations in-line without compromising efficiency. Our manufacturing professionals has developed unique skills and our owners are long-term and investment willing, making sure we’re one step ahead.


  • Unique technology
    We build our own processes ensuring full ownership to the technology. In-house design, building and programming of advanced machinery with robotics-, laser- and vision systems. Lean / Six Sigma philosophy and standardized process parameters ensures efficiency in manufacturing.
  • Welding quality
    ISO 3834-2 certified (Quality requirements for fusion welding) manufacturing plant with WPS procedures supported by WPQR. Fully automated welding processes with 100 % control of key parameters in line. Minimal discoloration of HAZ post-weld. Full passivation of tanks, flushed with de-ionized water.
  • Process control
    Manufacturing in Norway has its advantages – we started automating 40 years ago. Today we’re one of a few system integrators for KUKA Robotics. Automation provides us with the unique capability of implementing 100 % process control for all CTQ operations in line – without compromising efficiency.
    Don’t just take our word for it – independent third party certifications gives our customers peace of mind.
    • OHSAS 18001  (Health and Safety)
    • ISO 9001                   (Quality)
    • ISO 14001                 (Environment)
    • ISO 3834-2                (Welding)

Innovation timeline


Norway’s first autogenous welded storage tank is produced at Oslo Svesiebedrift.


Welded cooking pots and wood boilers complements the range of products.


Development of wood-burning boilers which provides both heat and hot-water.


Production of potato collector cogs and planting equipment during the war.


Production of copper-lined storage tanks 200 – 50,000 liters resumes.


Provision storage tanks tripled the capacity while only taken half the space.


“TRIPLEX” and “COMPACT” heating units for oil and wood/electrical units.


“NORTHERM” integrated heating unit and storage tanks is launched.


The “SAFE” system with its triple-valve and surface mounted thermostat is introduced.


First in the world to produce stainless steel storage tanks which increases lifespan.


First in the world to produce stainless steel storage tanks which increases lifespan.


The “SUNSAVER” solar-heated storage tanks are launched.


Top-mounted mixing valves becomes standard, resulting in huge resource savings.


The tank-in-tank unit “PROGESSS” water heater line is introduced for heat pumps.


The “TURBO” system with plate exchanger revolutionizes heat-up times.


The “EXPRESS” storage tanks with flip/flop thermostat heats water 3 times faster.


The “UNIVERSAL” electric boilers 15-45 kW without contactors makes installation easier.


“THERMO TOP” reduces heat loss from standard storage tanks by 20%.


The “MAXI” large storage tanks 500-1000 liters becomes industry standard.


The warranty is doubled on the stainless steel pressure tank.


ECO FOAM saves more than 500 million kWh in heat loss over 10 years.


“ENERGY SAVER” for grey water reuse results in huge Energy Efficiency savings.


The “OPTIMA” line triples the capacity and increases the efficiency for heat pumps.


“EXPANSION” is introduced with a fully integrated expansion solution.


“OPTIMA TRIPLE COIL” is the industry’s most advanced heating central.


The “DELTA” series receives rating “A” from ErP – best in class.


NANOPUR and VACUUM panels saves 200 million kWh over 10 years.

The future

The development never stops, and OSO has a lot of exciting things, we look forward sharing with our customers in the future


Company philosophy

Our vision: Stainless steel water heaters with market-leading quality and efficiency.

People & Nature

“The future will either be green, or not at all” – Bob Brown.
Norway’s first environmental enterprise with 50-year efforts in uniting people, environment and industry. Thanks to loyal support from our customers, OSO has become synonymous with hot water and environmental protection. Pure well-being from our products made with minimal use of resources demands that we construct the best and most efficient heating products on the market. Our fundamental thinking comes out of love for our nature: to be the best for people and environment.

We are proud to give our contribution to Protect our Beautiful World. THINK FUTURE.

Innovation & Technology

“Complexity is not to be admired, it is to be avoided”- Jack Trout.
OSO has introduced every water heater innovation in Norway over the last 85 years, and is also a leader in development of production technology for stainless steel tanks. Product innovation and technology development is the center of our business. Ownership of the technology is an essential competitive advantage in the world’s most expensive country for manufacturing. The main goal is that all our products and solutions are as easy as possible for the installer and the user.

By seeking new and better solutions we secure the company’s existence. NEVER FOLLOW.

Quality & Service

“Price is what you pay, value is what you get” – Warren Buffet.
OSO was the first in the world to produce stainless steel hot water heaters. More than 4 million OSO products have shown outstanding dependability and life cycle economy over that last 50 years. Experience, high-tech production and unique welding technology ensures that we deliver quality products. That’s why we guarantee the stainless-steel pressure tank for 5 years.

We provide exceptional service which leads to long-lasting relations with our customers. SIMPLY BETTER.

Our strategy

Over 85 years OSO Hotwater has earned the trust from suppliers, co-workers and customers. We are still going to earn, and manage, this trust in an exceptionally good way, and value the opinion of our partners.

Our guiding targets:

1) Safe products, manufactured by safe processes

2) Class leading quality and efficiency

3) Correct products delivered on-time

4) Cost- and energy efficient processes

Strong partners

OSO cooperates closely with all the leading players in the distribution, installation and service of the plumbing industry. Our products are used freestanding or as part of complete heating systems in combination with air-water and liquid-water heat pumps, solar collectors, district heating, gas boilers or electric boilers. We always recommend that a professional install our products to ensure a good end result that provides clean well-being for decades.

Company certifications

OSO Hotwater holds a number of certifications that shows that targeted work towards quality, outer environment, workplace environment and processes yields good results. In addition, certifications and cooperation with the National Institute of Technology are important external inputs and quality assurance of the work we do throughout the year. We are proud of the certifications our continuing work in process improvement, which includes:

  • ISO 9001             Certification of the company’s quality system and management.
  • ISO 12001            Certification of the company’s environment control system and objectives.
  • ISO 3834-2          Certification of the company’s welding processes and material selections.
  • OHSAS 18001     Certification of the company’s workplace environment management system.

OSO is also adhering to ISO 26000, an international standard and guide for CSR.

Product certifications

OSO invests more resources to safeguard the products than is required. Storage tanks and components are stress – and performance tested equivalent to the expected life time of the product. Incoming Quality Control (IQC) is performed on all critical components, process quality control is performed during the production (PQC). Pressure testing with 1.5 times the design pressure, electrical outgoing control and testing (OQC) are performed on all products. The end result is the well-known OSO quality, which has proven an outstanding life cycle economy thorough the last 50 years.

For additional reassurance for the customer our products have a number of certifications (depending on the product model):

  • CE mark               Product compliance (performed by the manufacturer) to European standards
  • EMC: Electromagnetic Compatibility
  • LVD: Low Voltage Directive
  • PED: Pressure Equipment Directive
  • RoHS: Restriction of Hazardous Substances
  • REACH: Registration, Evaluation, Authorization and Restriction of Chemicals
  • NEMKO mark    Product compliance to European safety and EMC standards
  • WRAS mark        Product compliance to United Kingdom water regulations & safety standards
  • AHRI mark          Efficiency rating to AC, Heating, & Refrigeration Institute standards
  • ETL mark             Product compliance to North American safety standards                                         
  • CSA mark            Product compliance to Canadian Electrical Code


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