About Us

3One Company was set up by Guy Hay to offer the professionalism and knowledge of a large, highly-qualified heating engineering firm with the friendliness and value offered by smaller heating companies.

Prior to founding One Company Heating in 2007, Guy worked for 10 years for two reputable heating companies. His second engagement with a large heating company allowed him to expand his skills and gain competency in renewable energy technologies as Senior Heating Engineer and after 5 years expanded his skill to become Installation Supervisor and Surveyor.

One Company’s customer service approach is two-fold:

  • Firstly, we assess your heating requirements, based on your house, budget and personal preferences.
  • Once we’ve recognised the comfort levels required, we provide a solution using high-quality, easy- to-use and energy efficient products.

We promise a smooth and tidy installation, which on completion is followed by a “no-nonsense” explanation and 4demonstration of your new heating system – as well as all the necessary paperwork required. All work is guaranteed to the highest standards.

Why One Company?

One Company enables customers to have a dedicated and knowledgeable installer, experienced in all heating technology options and offers the unique service in seeing an installation from survey, through installation, commissioning, handover to ongoing service.


One Company is a plumbing and heating installation service based in Hertfordshire, and covering the surrounding areas. We are dedicated to providing a high-quality service to customers.

Services offered

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  • Complete Heating Installation (Gas, Oil, LPG, underfloor heating, solar hot water, Biomass and ground/air source heat pumps.)
  • Commissioning Heating Installation
  • Fault Finding and System Repairs
  • Service and Maintenance
  • Pressurised Hot Water Installation
  • Installation Partnership with Grant UK Oil Boilers, Viessmann Gas Boilers and Mitsubishi Electric Ecodan Heat Pumps
  • System Cleansing and Power Flushing of Radiators and Domestic Water Systems
  • Landlord Certification and Gas Safety Checks Heating surveys
HETAS is the official body recognised by Government to approve biomass and solid fuel heating appliances, fuels and services, including the registration of competent installers and servicing businesses.