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How inaccurate accounting of our carbon emissions is harming the environment and the bottom line for business

Evidence confirms watching television during winter nights is worse for the environment than on a sunny afternoon, and that LED lighting is more effective than installing solar power to reduce carbon emissions.


05 April – A new study has revealed that the current system for measuring carbon emissions from buildings and businesses produces inaccurate results that have an impact on our environment and balance sheets. The study, by sustainability consultants at WSP | Parsons Brinckerhoff, found that there are substantial inaccuracies because the current system does not take into account the variability of carbon emissions, which depends on when we use energy from the electrical grid. 

The inaccuracy this causes may lead to poor decision making for new developments and investments, increase CO2 emissions, and holds back the development of energy storage and smart management of energy demand. It also has financial implications for companies that pay the climate change levy based on a non-variable flat rate.

How the system currently works

At present it is standard to use a single number for calculating the CO2 emissions of energy that we use. The climate change levy is charged per kWh amount of electricity or gas we use, regardless of when we use it. UK building regulations and the greenhouse gas (GHG) protocol also take the same approach. In reality, energy usage, particularly electricity used at different times of the day, season and year, differ in terms of CO2 emissions massively.

The environmental implication is that two buildings or businesses using the same amount of energy could be unknowingly producing very different levels of carbon emissions whilst being charged the same amount through the climate change levy. Further, companies that are trying to reduce CO₂ emissions by using energy storage measures will be paying more in climate change levy and reporting higher CO2 emissions than those that aren’t as calculations are based on how much energy is used, not when it is used.

Why carbon emissions vary

By comparing the CO2 emissions for every (half) hourly period over the year it is possible to see differences in intensity levels (see diagram). For example, in winter evenings carbon-intensive energy (such as coal) is required to meet the demand for electricity in homes, which isn’t as high in summer afternoons, when cleaner energy such as solar is more common.

Therefore turning on the television in the middle of the day in summer will have far lower carbon emissions than during the evening in winter.

Diagram 1: Daily carbon intensity fluctuations by month

Diagram 2: Projected carbon intensity of electricity by year

Different carbon reducing measures, whether through energy generation, energy storage or demand reduction will have varying impacts depending on the time of day, the season, and even the year. As the electric grid decarbonises (Diagram 2) organisations will have to consider what tactic should be implemented, whether in residential, retail or commercial context, to provide the best CO2 emissions savings (see case study).

Case study – LED Lighting vs solar power

Generating electricity via solar panels and the retrofitting of LED lighting (demand reduction) are two tactics currently used to reduce carbon emissions. While solar panels can work effectively to generate electricity, this is most often during the summer and during the middle of the day, when overall electricity demand is low because people are generally not at home. During these times many of the more carbon-intensive forms of electricity generation such as coal are “offline” or at reduced output. Solar power is therefore displacing relatively cleaner forms of generation such as gas.Conversely, during a winter’s evening, there is typically no solar generation, and more carbon-intensive systems will be retained in order to provide generation to meet peak demand. Therefore a kWh saved through LED lighting will be more effective in reducing emissions than adding a kWh generated by solar. This tactic therefore better enables our energy to be cheaper by reducing our demand for energy at peak times.

Barny Evans, sustainability and energy expert at WSP | Parsons Brinckerhoff, said: “This matters for people at home and for global corporations. Buildings and businesses are under increasing pressure to meet legal requirements to reduce emissions, but it’s not as simple as counting a single number. Organisations with specific goals such as carbon neutrality will find their current accounting is unknowingly leading them to take policies and actions that result in higher or lower carbon emissions than they realise.”

“As technology advances and the grid decarbonises we need to move to a system that better recognises the benefit of carbon reducing measures including energy storage and demand reduction. By taking into account when energy is being used we will have the opportunity to not only work out how to reduce carbon emissions but also our bills.”

Notes to editor

For media enquiries please contact Tom Hawkins on 020 7314 4585 / tom.hawkins@wspgroup.com

WSP | Parsons Brinckerhoff is one of the world's leading engineering professional services consulting firms. Our 36,000 people, based in more than 500 offices, across 40 countries provide engineering and multidisciplinary services in a vast array of industry sectors, with a focus on technical excellence and client service.

In the UK, 7,000 people (including Mouchel Consulting) provide consultancy services to all aspects of the built and natural environment working across both the public and private sectors, with local and national governments, local authorities, developers, contractors and co-professionals. The combined business has been involved in many high profile UK projects including the Shard, Crossrail, Queen Elizabeth University Hospital, the Bullring shopping centre in Birmingham, the re-development of London Bridge Station, Manchester Metrolink, M1 Smart Motorway, and the London Olympic & Paralympic Route Network.




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