Blog Post

A cool 91% energy saving from our new air conditioning units

One of our recent Salix grant-funded projects entailed the replacement of 12 air conditioning units with 10 new, high efficiency units, yielding an impressive 91% saving in the energy that they use, with a carbon saving of 9.68 tCO2e per year.

Our analysis conducted as part of the project also highlighted the important interplay that exists between technology and human behaviour, illustrating that as well as upgrading technology to improve efficiency, we can all do our bit to avoid wasted energy and minimise carbon emissions. In this blog we provide further information on the project and steps you can take to do your bit. By joining our online platform Doing #UoR Bit ( you could even be in with a chance to win a prize!

The Rationale

The heating and cooling systems in buildings across the University estate are very important as they enable appropriate temperatures to be maintained to support the comfort, wellbeing and productivity of our building users. However, use of these systems is energy intensive and is therefore one of the key areas identified for improved energy efficiency within the University’s carbon reduction plans. The goal is to reduce energy consumption whilst maintaining comfortable conditions, and this is generally achieved through improved efficiency of systems.

The Project

This project focused specifically on 12 aging and inefficient air conditioning units which were replaced with 10 high efficiency models in rooms across a number of the University buildings. The savings were achieved through:

  • Removal of two units without replacement due to a change in the use of the space, meaning these no longer require air conditioning.
  • More appropriate sizing of the new air conditioning units.
  • Selection of modern units with high efficiencies, enabling the required cooling load to be met with a lower electricity demand.
  • Improved controls to help ensure that the units are only running when needed.

The Savings

This project has yielded an energy saving of 41,538 kWh per annum associated to use of the units, which is equivalent to removing the electricity demand of 14 houses from the grid!* Completion of this and many of our other recent projects has been timely, due to the substantial increase in energy costs. The initial cost savings calculated were £6,314 per annum based on 2021 energy prices, but this has increased to £10,509 per annum based on 2022 rates.

The Human Factor

System efficiency is not the only factor to consider when reducing energy consumption. It is also important to ensure equipment is only being used when there is a need. During our analysis we identified that there were instances of air conditioning units being left on after a room was vacated and no longer in use, or overnight. Leaving equipment running when it serves no useful purpose is one of the biggest ways in which energy is wasted and is completely preventable through action being taken to switch things off.

Doing #UoR Bit

For the new units installed, these have been fitted with occupancy sensors which act as a fail-safe in the event that the air conditioning is not turned off, by automatically turning them off after a period of no occupancy being detected. However, many other systems in the University do not yet benefit from these controls and depend on people manually turning them off when not required. There are steps that we can all take to support this including:

  • If you are last to leave a meeting room, classroom, lecture hall etc. at a time when it is going to be left vacant, or it is the end of the day,  turn off air conditioning systems (and other equipment such as lighting, computers, heating etc.).
  • If you are aware of spaces in which air conditioning or heating systems have been left running and it is not clear how to turn them off, or there appears to be a problem with the system controls please report this to: .
  • Set air conditioning and heating systems to appropriate temperatures. The harder a system has to work to heat or cool the building, the more energy will be used. Think about your clothing and dress appropriately for the weather/temperature to avoid requests being made for greater heating or cooling of the space.

When taking actions to save energy don’t forget to log these to earn points at

  • To read the full analysis on the savings from the air conditioning replacement report, please click here.
  • To learn more about the other Salix projects, you can read the introductory article here.

 *Typical Domestic Consumption Values (TDCVs) are industry standard values for the annual gas and electricity usage of a typical domestic consumer. The latest figure released by Ofgem (2020) is 2,900 kWh electricity use for a medium sized house.

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