About a year or so ago, my brother bought a new property and installed solar on the roof.
“You should do the same” he told me, “it is one of the best financial investments you can make” (he is a mathematician).
So I contacted a local firm to see what they would say.
What they said was (as we had anticipated) that our roof is too small (the biggest roof has a dormer window in it, making it unusable) and faces the wrong way.
Until solar panels become more efficient, solar energy is not a good investment for us.
But, they told us, you could save money by installing batteries.
Our all-electric house
We are all electric. Gas terrifies me, and we had it taken out a few years ago. However, despite having a small house, our electricity bills are horrendous.
- My son feels the heat and is dependent on his air conditioner unit in the summer.
- I feel the cold and need a lot of heating in the winter (and in the spring and autumn too!).
- We all use our computers a lot.
All of which costs.
Reducing our bills via batteries seemed a very good idea. So in January, we had three Fox batteries installed on a wall in the back garden.
The installation
There were problems at the start. I had assumed that we would be able to sell electricity back to the grid, but after extensive correspondence, both with Octopus and the installers, I finally had to accept that this was not an option for our installation.
I was not pleased.
I also found the terminology and software baffling. I did not really get a grip on it for a couple of months, after extensive discussions with ChatGPT.
However, we have now put all that behind us, and the system is proving itself to be a real money saver.
The Fox Battery System
Thankfully, our installer used Fox rather than Tesla batteries!
The batteries are pretty big. You can see an image of them above. One of my complaints about the installation company was that the guy who came out initially seemed to think they would fit in a cupboard in my office!
However, they are fine in the garden and are also a useful place to put potted herbs.
You control them via an app. To do this, you need to be signed up with the Octopus Agile tariff, which tells you what the price will be for every ½ hour of the day.
You then check this every day and tell the app when you want the batteries charged up. Then the charged batteries supply you at the times when the prices are high.
The variable electricity prices
It’s fascinating to see how the electricity prices vary from day to day. The only real constant is that the highest prices of the day are after 4:00 pm. So long as you can avoid buying electricity during that time, you are bound to save money.
The Octopus App shows you the electricity prices for today and (after about 5.00 pm) what the prices are going to be tomorrow. You can then set your app and tell it when to charge.
The App has a visual image of the prices and then below you can scroll down and see the prices set out in half hour chunks.
It’s not always the case that the cheapest electricity of the day is during the night. See the three images below, which are for the past 3 days.
- Day 1 is very cheap before 4.00 pm, but the cheapest time is in the afternoon.
- Day 2 is fairly constant for most of the day, apart from a dip before 4.00 pm, followed by a more expensive period for a couple of hours
- Day 3 has a small dip in prices in the early morning and a big dip in prices in the afternoon
Excitingly, sometimes prices go negative, meaning that if you are able to cram all your battery charging during that time, Octopus is paying YOU for the electricity you use.
For example, on Day 1, there were a few negative prices in the afternoon, bringing my bill for the day down to £1.09. I have only been able to manage one totally negative price day so far, which was 25 May when my bill was -£0.93p. But hopefully there will be more.
The main problem is remembering to set the app. Although if I forget and it uses the day before setting, it will always avoid the expensive period after 4.00pm.
What are our overall savings?
I have only really been using the app properly since February 2025, but our savings during the past five months, compared to last year, are £918.
The system cost £8,000, so at this rate, the system will pay for itself in just under 4.5 years.
Could this be used by landlords?
I don’t see why not. So long as there is somewhere on the property where the batteries can be installed.
Either the tenants could have control of the app. Or if the landlord includes the electricity cost with the rent, the landlord could control the app.
And finally
Despite the hiccups at the start of our battery experience, I am really glad we have them.
Not only are we saving quite a large sum on our electricity bills, it is also nice to think that in a small way we are contributing to Net Zero.
Renewable energy (eg solar and wind) fluctuates over time. Meaning that any system where electricity is being bought during a time of plenty and the stored energy used during a time when it is in short supply, will be beneficial for UK energy overall.
If everyone had battery storage, the inevitable fluctuations with renewables would not be a problem.
If you can install solar as well as batteries, you will get even more savings and can also sell electricity back to the grid.
However, it is good to know that even if, like us, solar is not practical at the moment, there is another solution.
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