Case Study: Milton Keynes Couple Cut Energy Consumption by over 30% with new renewables transformation of home

January 31, 2024
11 min read

David and Ros from Furtzon, Milton Keynes aimed to live off the Gas Grid; here’s their story. 

Customer Satisfaction is paramount to how we work at Green Building Renewables- when it comes to customer service, we want to be the best renewables installation company. Case Studies from our customers bring to life the work we do.  

In this case study, Milton Keynes couple David and Ros, who live in Furtzon, tell us about the renewables transformation they have undertaken at home and the benefits they have already seen. 

Why did you want to transform your home in Milton Keynes with renewable technology? 

The solar panel system was part of a larger purpose and ambition to reduce our use of fossil fuels at our home in Milton Keynes. We already had an electric car as well as a hybrid car. But, we aimed to get off the gas grid completely and use only electrical energy from our renewable sources and, when necessary, from a renewable supplier.  

Our energy transformation project would involve a heat pump, a solar PV array and a battery storage system. Our renewable transformation is a part of an even larger project. We also have to install a rainwater harvesting and water conservation system at our home in Milton Keynes.  

We decided very quickly that ground source, although our preferred technology because of its immunity to seasonal variations, was impossible due to access to the garden, the borehole cost, and the disruption it would have caused. Instead, we opted for an air source heat pump. We had the perfect location for the unit and easy access to the existing heating system. 

Ros and David Furtzon home in Furtzon, Milton Keynes

What benefits have you experienced since having the technology installed?    

The benefits of the ASHP have been significant already.  

The system has only been commissioned for a couple of months, but already we feel warmer all day and night, even though there were several days in the last few months where the temperature did not rise above freezing in Milton Keynes.  

Our energy consumption and costs are significantly down compared to the same period last year.  

Gas consumption last year was 1926 kWh, and total consumption, including the electricity for the house, was 2457 kWh. In comparison, this year, we have only used 1422 kWh of electricity and, of course, no gas. That’s a total energy consumption reduction of over 40%.  

The battery storage system, or our battery bank as I call it, has also been transformational. We have been able to charge the system overnight at the Economy 7 off-peak rate and then use that charge during the day. We even have spare electricity stored when we go to bed. So, at peak rate times, we have also been off the grid for electricity.  

Our electric car also charges off-peak, so we do not inefficiently discharge one battery to charge another! The panels are used during the day to top up the batteries. The result is an endless supply of hot water any day or night and adequate heating throughout the house.  

The cost of this energy is only 65% of what we paid for this period last year. The overall cost of a kWh of combined energy last year was 15.5 p and this year 17.3 p. That is slightly higher, but the more efficient use of energy has more than offsets this. 

David and Ros reduced their need for Gas completely and their total energy consumption by 35% when compared to the same period in 2022

Regarding our solar system, whilst it is winter and the system has only been installed for a few months, it is difficult to assess the full impact of the installation. However, what I can say is that even during winter, on sunny days, we have been able to generate as much as 15 kWh.  

Based on my graphs and calculations, which include seasonal changes, our location in Milton Keynes, the last three years for daylight hours, and cloud cover data, the predictions look good to generate our 9800 kWh annual target. And if my calculations are correct, it could be a lot more. 

Peak generation in the summer months, accounting for the local Milton Keynes climate, is about ten times that of winter. So, ask me again in another five months! 

How did you find the installation process?  

When you have as much installed as we did at our home in Milton Keynes, it would be unrealistic not to expect it to be quite disruptive! We expected disruption so we prepared for it.  

We had to do several things to enable us to maximise the installation of the new technology. We had to upgrade about 5m of cold-water supply pipe from 15 mm to 22 mm diameter. This was located between the landing and the airing cupboard.   

The disruption, however, was minimised by having previously used my own endoscope through a few exploratory holes drilled in the floorboards from above and up through spot-light fittings from below to search out the gauge and route of the existing pipework. As a result, the installers knew exactly where to cut.  

We also needed to replace 90% of the plumbing in the airing cupboard to accommodate the modern, stainless steel, pressurised hot tank. There was also the requirement of locating the return from the radiators, which required additional and unexpected routing of pipes.  

Eleven radiators were also upgraded to bring all our rooms to the 3* rating necessary to qualify for the £7,500 BUS scheme. 

The actual fitting of the heat pump and the solar panels was not disruptive because that was all outside. 

We often had four men working on all the technology being installed, and despite the amount of work undertaken, we were never without hot water, even on the day the tank was changed. Step-off, disposable flooring was used throughout to minimise dirt from feet making it into our Milton Keynes home. Little things like that mattered to us.  

Most of the electrical work was done on the roof and garage, affecting us little.  

The scaffolding even allowed us to conduct a big clear-up operation of the moss on our roof and gutters. After the scaffold was removed, several buckets of moss from the gutters and extensive window cleaning were needed.  

How long did the installation take?  

All the renewables were installed over two weeks, slightly extending into a third calendar week. The scaffold was removed at the end of the third week. It sounds like a long time, but when you consider the amount of technology installed: a large heat pump (14 kW), tank (290l), a 34 solar panel array, a 54 kWh battery bank, and a 3-input string inverter it is very impressive.  

What advice would you offer to others considering renewable technology for their home? 

Knowing what you want before you look for suitable installers is important.  Taking an active interest in the work throughout the project and from the start will help with your knowledge. Do you want to install renewables to impress the neighbours? Because it’s trendy? To get a government grant? To save money? To stop using fossil fuels for the sake of the environment? Be clear about your motives; otherwise, you risk not getting what you want or need. 

When it comes to the cost, you must see it as an investment in the property and the environment. It is not cheap, and we must wait for our return on investment. But I take pride and comfort in knowing we are one less house now using fossil fuels. 

One important thing to understand is the mindset change needed for living with a heat pump heating system compared to an inefficient fossil fuel boiler.  

An ASHP works best when only requested to change the temperature about 3°C at a time, and the hot water is left on all the time. So, it’s best to set it at 19°-21 C during the day and 16°C overnight. This, and the need for the pump to go through the occasional anti-legionnaire cycle, defrost, and water heating, will mean it will be coming on at times during the night.  

Heat Pumps installed outside Milton Keynes home
Solar Panel Array installed on the Milton Keynes home.

What is your opinion of Green Building Renewables? 

From start to finish, I found them a highly professional, proactive, and courteous company to work with, and ‘work with’ is the key. 

As a former professional physicist, I was really clear on what I hoped to achieve, which I laid out to GBR as my ‘dream’. They then made this dream possible with a realistic installation that satisfied us both.  

I know I had many technical questions and was willing to challenge assumptions about respective equipment capabilities. The answers provided satisfied me that they knew what they were talking about. 

I also learned a lot from the technological side throughout and had to rethink a few of my assumptions, usually in an incredibly positive way: discovering things the systems could do that I had not even thought about. 

Throughout the installation phase, I was delighted with how they prepared for work, carried it out, and tidied up afterwards. The engineers were particularly helpful in sharing information as I queried particular aspects of the installation, and we had a few occasions where we made joint decisions about a particular challenge that presented itself. 

I would particularly commend Ryan for his plumbing and David for his electrical installation skills. Both guys were passionate about their expertise and knowledge of the systems they were installing. They also took special pride in completing their respective installations to a professionally high standard and to look aesthetically pleasing, like works of art! And, of course, thanks go to Matt for his helpful management of the whole project from inception to aftercare. 

They, and their supporting team – mainly Ollie, Leo, Liam, and a couple of others – were always courteous and willing to help. 

I would wholeheartedly commend the local Daventry team to others in the area and I hope others have the same pleasant encounter with a professional, reliable and passionately environmentally conscious organisation that we did.  

What renewable technology did we install in Milton Keynes? 

At Dave and Ros’s Milton Keynes’ home, we installed the following technologies: 

  • A 13.7 kW Solar PV system including 34 x 405w LONGi black mono panels. 14 x 405W panels were installed on the front of the property, and 20 x 405W panels, in 2 rows of ten, were installed on the rear. The front array will accommodate two small dormer windows. 
  •  FOX G800 8kW Grid-tie inverter 
  • A 54kWh Tesla Powerwall 2 battery storage system including: 1 x Tesla AC Powerwall 2- 13.5kWh and Gateway Storage 1ph PACKAGE and 3 x 13.5 kWh Tesla batteries 
  • A 14kW air source heat pump system with 300l cylinder including Mitsubishi Ecodan 14kW air source heat pump, FTC6 programmable room stat which includes weather compensation, Erp A+ rated circulation pump, 300L Joule domestic hot water cylinder, Flexible hoses, Anti-vibration feet, TF1 filter, Honeywell 4044c three port valve, Isolation valves, Expansion vessel and Insulated pipework 
Tesla Powerwall Battery Storage Solution
Tesla Powerwall Battery Storage Solution

We also completed and provided

  • Application to the Boiler Upgrade Scheme (BUS) for the £7,500 grant 
  • Electrical testing and certificate. 
  • MCS certification 
Watch this video from one of our suppliers on how the BUS scheme works

Dave and Ros invested in an extremely comprehensive system to achieve their goal of living off the Gas Grid and transforming their Milton Keynes’s home. If you have ambitions to dramatically reduce your fossil fuel footprint and progress to a smarter, cleaner and greener home whether you are in Milton Keynes or elsewhere in the UK, then get in touch. We can help you.  

Written By:

Sarah Taylor, Group Project Support Manager
Sarah Taylor
Sarah’s experience predates the formation of Green Building Renewables. She was a critical member of the management team that rebranded to GBR. It was the allure of a new challenge and the chance to make a difference in a family business which propelled her entry into Green Building Renewables during a dynamic phase in the industry. Want to know more about Sarah? Click here to find out more : Read More

Reduce your energy bills with Renewable Technology

Speak with a member of the team today and we can talk through the options available for you.

Contact Us Today