CAT Senior Lecturer and Short Course Tutor Dr Alan Owen explores how our Renewables for Household short courses can help people save time, money and frustration finding out what renewable energy options will work for them.
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From average household to net-zero super home
CAT graduate Paul Martin shares his journey towards net-zero in his 1960s three-bedroom semi, showing that a modern low-impact lifestyle is possible for an average UK household.
In 2010, motivated by my visits and studies at CAT, I decided it was time to take steps to reduce my personal contribution to climate change. During my BSc, I recall seeing a case-study of a house in the UK powered by solar photovoltaic (PV) panels with surplus charging an electric vehicle (EV), and I thought, “I want to do that!”
Taking the first step
The first step was to understand my energy use. I did this by paying closer attention to my utility bills and taking meter readings for electricity, gas and water. I calculated the fuel consumption and annual mileage of my car. With the help of a carbon footprint calculator, I estimated the CO2 emissions attributed to my lifestyle (e.g. my diet and the things I was buying) and also to my share of UK infrastructure (services, roads, hospitals etc.). Using this information, I began to estimate my CO2 fingerprint – a detailed breakdown of my emissions across different categories (Fig.1) – and my total footprint (Fig.2), allowing me to track my progress towards net-zero over the years.
I purchased my house in 1995. I had a full set of data for 1998 before I’d made any changes to the property, so I chose this as the baseline year to measure improvements against. In 1998 my household’s footprint was 10.7 tons CO2e per year.
Lifestyle changes
I first began looking at the impact of my lifestyle choices, as these can be the quickest wins. Using the carbon footprint calculator, I came to a baseline figure of 1tCO2e per year.
To reduce these lifestyle emissions, I needed to make some changes. I changed my diet to vegetarian (later becoming vegan) and bought organic, fresh,
seasonal food from local farm shops where possible. I moved my finances to ethical banks, supported environmental charities (including CAT), and began living by the three Rs – reduce, re-use and recycle.These choices reduced my annual lifestyle emissions by 50% or 0.5tCO2e per year. I generally found these changes simple to implement with little cost impact.
My household electricity use
Thinking about reducing my emissions at home, I began with my electricity use. Until 2012, all my household electricity was provided by the National Grid.
- In 2012 I installed a 1.8kWp (kilowatt peak) solar PV array on my south-east facing roof. I took advantage of the UK government’s Feed-in-Tariff (FiT) scheme at the time (now replaced by the Smart Export Guarantee (SEG)).
- In 2018 I installed a 4kWh lead-acid electricity storage battery to increase the proportion of the solar power I was personally using from 25% to 75% and reduce the amount I was exporting to the grid (after the six-year expected lifespan, I replaced the battery with a 13.5kWh lithium-ion upgrade).
- In 2022 I added a 1kWp secondary solar array on the south-west facing roof of my garage. I added more renewable power generation from a share in the Graig Fatha Wind Turbine Project.
All these measures were self-funded. But the payback in energy cost savings and revenue from the FiT and turbine provided funds for more measures.
As a result of these changes, my annual household grid electricity energy consumption has reduced by 34%, and my house’s emissions have been cut by 0.8tCO2e per year.
Heating
In 1998 the heating for my house and water were provided by an inefficient 1970s gas-fired boiler and radiators. There was no loft or cavity wall insulation. I had 1980s double-glazed windows and patio doors and leaky
wooden external doors.In 2005, before I began consciously taking efforts to reduce my carbon footprint, I made some home improvements. I replaced my front door and patio doors and bricked up a side door. I replaced a flat roof. I insulated the main loft with 150mm wool fibre. And I replaced the old boiler with a 90% efficient gas condensing boiler, new pipework and radiators.
Later, taking advantage of a Welsh Government grant, I improved the
building fabric heat loss and infiltration by installing cavity wall insulation, topping up the loft insulation to 300mm, and sealing up areas where air was escaping. I replaced the windows with A-rated, argon filled, low-emissivity double-glazed units, trapping heat and maximising passive solar gain.
Then in 2023 I replaced the 18-year-old gas boiler with a 5kW air-source heat pump, electrifying my space and water heating. To do this I made use of a £7,500 UK Government grant*. In the first year of operation, this provided a coefficient of performance (COP) of 4.01. Essentially, every unit of electrical input delivers four units of heat, an efficiency of 400%, compared with 90% for a new gas boiler.These measures reduced my annual space and water heating energy consumption by 84%, and my emissions by 2.7tCO2e per year.
Travel
As a wheelchair user, all my personal travel is by car. At the end of 2011 I changed my petrol car to a mild hybrid, saving 1.4tCO2e per year. Three years later, I was able to upgrade again to a 100% battery electric vehicle, saving a further 0.5tCO2e per year.
In 2024, due to a greater proportion of grid electricity coming from renewable sources, particularly wind, my annual car travel emissions were reduced by 79% or 2.2tCO2e per year. This is despite my mileage increasing by 4,000 miles a year.
The electric vehicle can also be charged purely from solar in summer due to the addition of the secondary solar array – zero cost, zero emissions.
Water consumption
I’ve reduced my water consumption through water harvesting, installing low-flow gadgets on outlets, the use of a shower timer, taking showers over baths, and using a dishwasher rather than filling the sink. My annual water consumption has dropped by 80%, resulting in emissions reductions of 0.04tCO2e per year.
Infrastructure
The infrastructure we use, like services, roads, hospitals and so on, have CO2 emissions attributed to them. These are not personally controllable, so they have remained constant over the period.
The figure was derived from the carbon footprint calculator I used – 2.75tCO2e per year for each UK citizen.
To offset some of these emissions, I used natural sequestration through an annual donation to the Woodland Trust to plant 25m2 of woodland. I planted 14 native trees on-site, created two ponds, grew a green wall, and put an extensive sedum green roof on my flat-roof extension. I’m fortunate to have a large garden which allows me to do these things.
Overall impact
Due to the measures described above, by 2024 my total carbon emissions
had been reduced by 79% or 8.5tCO2e per year compared with the 1998
baseline, from 10.7tCO2e to 2.2tCO2e.Furthermore, my personally controllable emissions, omitting infrastructure, produced a negative figure of -0.5tCO2 e in 2024. Fig. 2 shows the carbon emissions reduction over the period, comparing my total footprint, personally controllable emissions, and the UK per capita target.
Fig.2 My annual CO2e emissions from 2011 to 2024, including the 1998 baseline
My home and lifestyle are now fossil-fuel free, and the house is one of the SuperHomes, a network of energy efficient retrofitted homes assessed by the National Energy Foundation. I now have that house that is powered by solar with surplus charging an EV – mission accomplished!About the Author
After studying a BSc Environmental Studies and Diploma in Environmental Policy then an MSc Sustainability in Energy Provision and Demand Management at CAT, Paul now writes articles and a blog at ecofuturist.net about achieving his net-zero carbon lifestyle. He is also a co-founder and director of EVA Cymru, Wales’s national representative body for electric vehicle owners and drivers.
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Transforming community energy decision making
To move from fossil fuel use to local renewables, communities need the right knowledge, skills and tools. CAT graduate Anna Hartley introduces CELESTE, a new system that enables anyone to explore the potential for renewable energy projects in their local area.
It is widely acknowledged that to meet global net-zero carbon goals and mitigate the worst effects of climate change, fossil fuels must be replaced as much as possible by renewable energy. While we hear a lot about large-scale multi-million dollar solar and wind farms owned and managed by corporations and states, small-scale renewable energy communities (RECs), in which citizens come together to produce, exchange and use renewable energy, have also been identified as a key component in this transition.
No two RECs are exactly the same, but the EU describes them as legal entities that combine both non-commercial economic aims with environmental and social community aims. They share open and voluntary governance, shared ownership and control by members (who are also consumers), and have as a main purpose creating social and environmental benefits instead of financial profits.
Sounds fantastic, right? Yet in France, where I live, RECs are little known and poorly understood. What if there was a programme that could fast-track the development of RECs while also raising awareness about energy systems more broadly? That’s the question I investigated during the dissertation period of my MSc Sustainability in Energy Provision and Demand Management at CAT.
Bridging the knowledge gap
Assessing a site for its suitability for a renewable energy project is not overly complex, but it does require some specialised knowledge. If we want thousands of small communities all over the world to start building them, it seems evident that there should be more tools available that can provide this.
I felt sure that by pulling together a range of freely available online datasets I could produce a program designed for non-expert users that would do simplified feasibility assessments for RECs. This should only require the users’ geographic location and their willingness to engage in some energy futuring to operate.
Harnessing digital tools
As the research progressed, my conviction that a tool like this was necessary and useful grew. Almost all the research and discussion around RECs focuses on their technical, economic and policy dimensions, with little attention paid to involving the broader public, who are the very people responsible for creating and running RECs.
Secondly, digital tools concerning renewable energy development are overwhelmingly aimed at expert users, very limited in scope, and often expensive to access.
By the completion of my dissertation period, I had created a prototype program known as the CELESTE Decision Support System. CELESTE stands for Créons des Énergies Locales, Écologiques, Solidaires et Transformatrices Ensemble (Creating Local, Ecological, Supportive and Transformative Energy Together).
CELESTE functions as an educational tool that uses the wealth of publicly available data, repackaging it in a useful way, rather than developing new complex systems. It is also modular and expandable, meaning that what is currently available is just the beginning and there is no limit to the number and type of modules that could be added.
Whether the user takes action after using CELESTE is up to them, but I hope they will at least feel more informed and engaged in the conversation around renewable energy. In this way, CELESTE is just as important as an engagement and educational tool as a systems modelling tool.
How does CELESTE work?
CELESTE has a simple interface and is designed to walk the user through four key stages, much like a carbon footprint calculator.
1. Start here: The user enters the name of their commune in France to view data such as the commune’s population, total energy consumption for the most recent year available (in this case, 2021), and the portion of that consumption that corresponds to the residential sector.
2. Adjust variables: Here, the user begins imagining their energy future, toggling different variables to see how these impact upon the commune’s electricity demand, such as the year (up to 2060), population predictions, climate change scenarios, and consumption patterns like electric vehicles and air conditioner usage. A bar chart clearly shows the actual electricity demand against the future demand as per what the user has inputted.
3. What’s possible?: At this stage, the user gets to start designing a new energy system. They are presented with a basic feasibility assessment for a solar PV or onshore wind farm in their commune. The user can toggle the size of the installation and see how this impacts physical size, what percentage of the commune’s electricity need this would meet, costing and payback time, and CO2 emissions reduction.
4. Next steps: Finally, the user is shown recommendations about ways to reduce their energy consumption, local and national organisations that support RECs, EC consultants who can begin advising them on their REC journey, and a list of RECs already functioning in their geographic area that they can visit and investigate.
What’s next?
CELESTE is still a prototype, built in Google Sheets and using predownloaded datasets for a limited number of communes. Many of the calculations applied to the data are quite rough, using rule-of-thumb estimates when trusted, peer-review data is missing. However, as better information becomes available, it can easily be integrated, improving the quality of the outputs.
Who can use CELESTE?
I have registered CELESTE under a Creative Commons licence so that it can be shared, adapted, and remixed by any non-commercial entity that wants to take it further.
While CELESTE is only currently crunching data for France, there is no reason why it can’t be adapted to anywhere in the world. Countries could substitute communes with their own administrative divisions, plug in their local electrical and population datasets, and adjust calculations – for example about typical electrical demand of an electric vehicle per annum, and the cost of renewable technologies – according to the most up-to-date information for their area.
No two countries will have the exact same kind of data, so it is exciting to consider the range of additional modules that could be designed and incorporated into CELESTE. Hydroelectricity potential, battery storage and grid flexibility, thermo-sensibility metrics, and access to local grants and subsidies are just a handful of the modules that could be added, given access to the right data and with the right minds on the job.
Furthermore, CELESTE could be used by existing RECs to see how their installations would perform under different climate, temporal and behavioural conditions, or by schools and institutions as an educational tool to improve understanding of the topic.
Explore CELESTE
About the author
Anna Hartley is an Australian writer who has lived in Paris and Beijing since 2011. Her work has been published in The Washington Post, France 24, Forbes Travel Guide, The Houston Chronicle, The New Zealand Herald, The Vancouver Sun, the Beijinger, and Babbel Magazine. She graduated from CAT’s Sustainability in Energy Provision and Demand Management in 2024.
CAT student dissertations
During their final year of study on a Masters in Sustainability at CAT, students explore a relevant topic in-depth by completing a final dissertation. This involves designing, investigating, and presenting an extended and independently conceived piece of research within their field of study. Equally important, the dissertation enables students to showcase the skills in critical thinking, data collection and analysis that they have developed throughout their degree.
The dissertation builds upon the current state of knowledge and some dissertations go on to be published in scientific journals or become the basis of further research. Students have also used the dissertation to explore the viability of a business idea or product that has a positive impact.
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Thinking Big and Acting Small – making waves in complex times
Can complexity science help us understand how to work together to create a fairer, more sustainable world? Author Jean Boulton, who will be speaking at the CAT Conference, explores…
Our communities are increasingly shaped by global forces – from pandemics and climate change to geopolitical conflict, discrimination and the far-reaching impacts of neo-liberal economic policies. Some of these challenges – such as the influence of the internet, the rise in extreme weather events, and the rapid spread of disease – are truly global in nature. Others, such as the impact of the war on Ukraine on wheat availability, or the impact on conflict in the Middle East on the Suez Canal, may be rooted in specific regions, yet have worldwide consequences.
These global conditions and crises also shape and compound policies of national government – in relation to growth, taxes, democracy, spending priorities; they also impact the responses of the corporate sector.
And yet for many of us, the one place we feel we can make a difference is locally, where we live, in our own communities.
Complexity Thinking in a Complex World
Jean Boulton, a regular contributor at CAT and a leading expert in complexity science, explores these questions. Complexity science emerged in the last century from the work of physicists and biologists seeking to understand how living systems – from organisms to ecosystems – emerge, stabilise, and sometimes spiral out of control. It also helps explain how systems dominated by powerful forces can lose diversity, become rigid, and face collapse.
These insights apply not only to the natural world but also to our social systems. They highlight the importance of connection, relationship, and inclusivity in building resilience. Stability, in this view, is not about control or top-down planning – it is dynamic and constantly evolving.
Exploring Food Security at CAT
Jean recently worked with a group of students at CAT to explore the issue of food security. The students first discussed the complexity worldview. Jean then introduced a method to connect the global with the local and explore the way the past shapes the present and the present shapes the future, in order to identify key factors and develop creative solutions.
Embracing Complexity in Everyday Life
So, what does it mean to embrace complexity in our daily lives?
First, we need to ask: what are the stable patterns we see around us – in culture, relationships, and ways of working? How did these patterns emerge, and how stable do they seem?At the same time, we need to stay alert to signs of change – the “new shoots” or “cracks in the fabric” that suggest transformation or even collapse. Embracing complexity means holding paradox: recognising what is, while also sensing into what is becoming. Daoist philosophy speaks of being attuned to “the beginning of the beginning” – noticing subtle shifts and emerging possibilities.
Understanding the present – even in its interconnected, systemic nature – is not enough. We must also pay attention to the “minute particulars,” as William Blake put it. We need to notice the new, the decaying, the possible, and the unexpected.
Walking the Path Together
In her book The Dao of Complexity, Jean explores the resonance between complexity science and Daoist cosmology, which emerged in the 5th century B.C.E. in China. A central idea is that “the path is made through walking” – we co-create the future through our collective actions and intentions. There is no single right way forward. The future is shaped by what we choose and what we do.
If we want a resilient future on this deeply interconnected planet, we must act with the whole in mind – with care for each other, for future generations, and for the Earth.
In these times of polarisation, increasing inequality, escalating climate breakdown, and an economic system built on individualism, these messages have never been more relevant.
Acting at the Appropriate Scale
E.F. Schumacher didn’t want his book to be called Small is Beautiful – he preferred ‘Work at the Appropriate Scale ’. While perhaps less catchy, it is, perhaps, a more accurate reflection of the challenge we face.
We must ask:
How can we act locally while keeping the regional and global in mind?
How can we use our local power to influence upwards and build solidarity across communities?
How do we find resilience and kinship, and protect the uniqueness of our local resources in a world of growing fragility and turbulence?
These are questions we must continue to explore together.
Author
Jean Boulton is a complexity scientist, author, academic and Fellow of the Schumacher Institute. She is a guest speaker at the CAT Conference.
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CAT’s collaboration with Local Community Renewables
Our partnership with local community energy group Bro Dyfi Community Renewables (BDCR) is helping CAT reduce emissions, cut costs, and explore new ways of managing energy on-site.
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More solar energy for CAT
As the demand for electric vehicle charging increases from our students and visiting groups, we are working with a local community renewables project to add around 50kW of new photovoltaic generation to our site’s power system.
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CAT Conversations – Dr Frances Hill
We recently interviewed Dr Frances Hill, Senior Lecturer and Programme Leader for CAT’s MSc Sustainability in Energy Provision and Demand Management, about her work teaching at our Graduate School.
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CAT Stories – Aber Food Surplus
Aber Food Surplus was co-founded by CAT graduate Chris Woodfield, and at our recent CAT Graduate symposium he joined a panel group to share advice based on his journey. He shares his inspiring story with us.
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Taking back power
Locally owned energy can provide a wide range of benefits, from reducing emissions to helping fund local initiatives. Paul Allen introduces a scheme local to CAT, Bro Dyfi Community Renewables, which shows what’s possible when communities come together to create change.
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Why we teach… community solar
Next in our series looking at themes and topics explored by students on CAT Masters degrees, Alan Owen introduces community solar, which we teach to students on a number of our postgraduate courses, including our Sustainability in Energy Provision and Demand Management MSc.
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