Recently one of our heat pump customers, Jerry, wrote a case study about his experience switching to renewables and how it has all been performing over the past year.
Thank you for allowing us to share your findings Jerry!
The Journey
In July 2010 we took the plunge and had an array of 10 solar panel installed. This setup has a maximum theoretical output of 2.2 kW, and we are getting about 1,800 kWh of electricity from it in a typical year. This on its own knocks about £300 pounds a year off the electricity bill and the Feed In Tariff in-payments amount to around £1200 a year.
It took less than 9 years to get back the original investment, and now it is all profit. We were very lucky to have been able to move quickly and get on the original Feed In Tariff as the scheme was only open to join for 9 months (it was just too popular - you can see why!). Of course, deals today aren’t as quite as generous, but these days solar panels cost a fraction of what they did back then, and they have twice the power output per panel. This makes schemes such as Smart Export Guarantee look interesting and with today’s much lower upfront costs, you can still get a reasonable return on your investment.
In December 2020 we switched to an electric car. This made it possible to transfer our electricity tariff to an EV specific one allowing us to get cheap rate electricity overnight to charge our car. It turns out the cheap overnight tariff was going to save us a lot more than just car charging, but more on that later.
In 2021 we replaced all our doors and windows with modern high-performance units. Before we had a mixture of poorly insulated and ill-fitting windows and doors, The new windows and doors not only greatly improved our heat loss they also look much better. Although that is the most expensive upgrade, we are very glad we did it.
The next step in July 2022 was to have a home battery system fitted along with a second small solar array fitted to our garage (in an east/west configuration, you can see the east array in the photo further on). The new solar panels have 73% more output per panel that the old ones do and although there are only 4 of them the produce around 65% the output of the first array, we also get a longer solar day, the east panels are good for the morning and west for the evening. Also, the battery allows us to run on solar and stored solar for a lot of the time in summer, only consuming 1 or 2 kWh of imported power from the grid each day. Furthermore, in the winter months we can charge the battery overnight on cheap rate electricity and run the house from that over the course of the next day, saving even more money.
Our house is a solid walled 1929 semi and in August of 2022 we had external wall insulation fitted. This consists of 90mm insulation fixed to the external walls and covered with a silicone render. After completing this step our house has improved from an EPC certificate rating of E to a B.
Our ultimate goal was always to move away from fossil fuels entirely and STOP BURNING STUFF!! In April of 2023 we were able to achieve this by having our gas boiler replaced with an air source heat pump. In fact, since last August our annual energy bill is less that the FIT In-payments we get form out first Solar Array. By March 2030 we will have recovered all the cost of the windows, doors, external insulation, solar panels, home battery and heat pump. Of course, whilst all of this hardly amounts to a tiny drop in the ocean when it comes to saving the planet, every little bit has got to help!
The Benefits of Renewables
My background is in Electronics, Data Comms and Computing, but for the last 12 years before I retired I spent most of my time involved in data analysis and reporting, so consequently I am a bit of a stats geek. I have kept detailed records of my energy usage and solar production since 2010 and am therefore able to quantify the exact benefits I am getting from each of our green investments.
Solar Panels
Technology moves on so fast and these days solar panels look a lot different compared to those from 2010. You can see the mostly black PV panels in the distance, compared to the original blue PV panels in the foreground. It is now possible to have entirely black PV panels.
Here are our solar cost saving and profit figures for the period from May 2023 to May 2024. The Bar graph showing the cost savings plus profit, the purple line is savings in imported energy (in kWh) and the black line the CO2 reduction in Kgs this has made.
The table below provides some extra details.
We have two solar arrays, the first was installed in 2010 and is fully amortised since 2019, the second system was installed in 2022 and will have paid for itself by 2028.
Both of our solar arrays were installed in a single day and caused us almost no disruption. We are fortunate in being early solar adopters and have benefited from the generous Feed In Tariff scheme. But solar is still a worthwhile investment. The current Smart Export Scheme can be quite a money spinner as well especially if you have a battery system too. Of course it’s not all about the bottom line - producing your own electricity from nothing but sunshine is such a cool thing to be able to do.
Home Battery System
We have had the home battery system for almost 2 years now. It is a 19 kWh GivEnergy system (2 x 9.5 kWh units) and a 3 kW AC coupled inverter. It only took a couple of days to install and now sits quietly in our garage just doing its job. We are so pleased with it. The battery enables us to run from off-peak electricity 90% of the time, which is not only a lot cheaper, but also greener as the grid is at its cleanest overnight. On top of that, by breaking the direct link between solar production and usage we can use 94% of our solar power ourselves and solar now accounts for about 35% of our total power requirements.
Not only does a home battery complement solar so well, but if you also have a cheap off-peak EV tariff then in can be great in the winter months too as you can charge it overnight on cheap electricity which can then be used to run the house throughout the next day.
Below are the figures for the last 12 months in both graph and table form.
Air Source Heat Pump
This was the final step in our electrification journey and has been a very easy and comfortable one. We have a Samsung 7kw unit that is controlled with a Homely Smart Controller that using our Smart EV electricity tariff heats our home in the most cost-effective way. The graph below shows our energy costs use and CO2 usage over the last 5 years. For the last 12 months the reductions are all due to the heat pump.
Our heat pump was installed in April of 2023 and took just over 2 weeks from start to finish. There was minimum disruption, no additional radiators were required, although some radiators had to be changed from single to double panel ones. We previously had a combi-boiler, so we also needed to find space for a hot water tank, therefore we ended up losing a storage cupboard. We have had the heat pump for a whole year now and our house has been lovely and warm throughout the winter, and we have always had plenty of hot water. It sits in our driveway tucked in behind the wall to the front garden very quietly doing its job (you can barely hear it from 2 meters away).
The 4 tables below provide month by month figures for energy use, cost and Co2 produced by both the heat pump and the gas boiler it replaced. The last of the four tables relates to cost savings. Because I also have a home battery system and a cheap overnight EV tariff my savings are almost £590 a year. However as not everyone who is considering a heat pump will necessarily be in such a position, I have also included costs for an Economy 7 tariff, which anyone could switch too and the standard flexible tariff that most people are on anyway. All the tariff I have used are from Octopus Energy and the rates use were those that applied at time.
Home Insulation
This was by far the most expensive home improvement we made if we consider the cost of the replacement windows, doors, and external wall insulation as a whole, but when we consider the entire package of upgrades against the savings it will still have paid for itself by 2030.
Our house is a 1929 semi with solid brick walls, so the only way to improve insulation was external wall insulation. The process took just over 2 weeks to complete and along with the new window that were fitted the year before has improved the appearance of the house (well, in our eyes anyway).
Below are before and after shots of our house, the rendering needed a refresh. It was cracked, flaking and very dull. The old windows had poor insulation and let the drafts. After making these improvements our gas consumption was cut by more than half. It also meant that the EPC of the house was improved from E to B which then qualified us for the Boiler Upgrade Scheme making the installation of an Air Source Heat pump £5000 cheaper (this discount has been increased to £7500 now!).
Conclusion
I think that it is obvious from my experience that most green technologies are complementary.
For example, while solar panels are good on their own coupled with a home battery system, they are terrific. You can be almost entirety self-sufficient in the sunniest month of the year. Furthermore, if you couple the battery with an electric vehicle and consequently and EV off-peak tariff (like Octopus Intelligent Go) and now that battery becomes great in the winter too as it can be charged up at the cheap night-time rate that can cut the electricity bill by more that 70%.
Our heat pump has a Homely Smart Controller which can make the most of our smart EV electricity tariff and does a good part of the heating and hot water using the off-peak EV tariff too. Owning an EV has enabled us to get onto this cheap tariff. The car costs can also benefit from the solar panels (remember, that is where we started). If you have a smart EV charger it can be configured to divert excess solar electricity into the car’s battery.
So, each component in the system assists and enhances performance of the other elements. While it is undoubtedly worthwhile to install any of these green technologies, the further you go down “Electric Avenue” the more benefits you can enjoy.
We have always early adopters of green tech, and it does seem to have paid off. Maybe it is just dumb luck, or just maybe It’s a good practice, who knows?
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