Solar battery storage without solar panels answers the question posted above.
In short, we charge batteries during the off-peak tariff and discharge them during peak time, thus saving money.
- Off-Peak Tariff: 21:30 to 02:29 unit rate = 8.25p/kWh.
- Peak Tariff: 02:30-21:29 = 40.75p/kWh.
Disclaimer: One needs to be on a tariff that offers an off-peak rate significantly less than the peak tariff for this to work.
Electricity bills have risen fast.
Suppose we rewound to December 2020.
- December 2020 – Traded in our ICE Vehicle for an EV.
- March 2021 – Switched energy providers to Octopus Energy. Peak (Day) = 18.35p/kWh, Off-Peak (Night) = 11.03p/kWh.
- May 2021 – Electricity price increase, Peak (Day) increased to 20.19p/kWh and Off-Peak (Night) to 11.50p/kWh.
- August 2021 – Octopus Go EV tariff enabled. Peak (04:30-00:29) = 14.4p/kWh, Off-Peak (00:30 and 04:30) unit rate = 5p/kWh.
There were a lot of doom and gloom predictions that gas and electricity prices would rise significantly.
- July 2022 – Our Octopus Go EV tariff came to an end. We needed to renew, but the quoted prices were ridiculous and much higher than the previous year. We decided to wait and see what the October increase would bring. (look at the renewal price for Octopus Go below versus our current price). ?
- August 2022 – Switched to Flexible Octopus. Peak (Day) = 31.97p/kWh, Off-Peak (Night) = 21.34p/kWh.
- We switched because Octopus Energy wanted to charge Peak = 35.55p/kWh and Off-Peak = 7.50p/kWh for the Octopus Go renewal. This was still a considerable increase from £828 per annum to £1306 per annum, but still cheaper than the renewal quote.
- September 2022 – Flexible Octopus Peak (Day) increased to 43.39p/kWh and Off-Peak (Night) to 16.68p/kWh.
- These were the numbers after the Gov. support. They were scary otherwise. Electricity per annum went up from £1306 to £1501. This was still cheaper than the renewal quote.
- October 2022 – Octopus Go Faster (5H from 2130) enabled. Peak (02:30-21:29) = 40.75p/kWh, Off-Peak (21:30 to 02:29) unit rate = 8.25p/kWh.
The above tariff added an extra hour, and we shifted the off-peak start time from 21:30 to 02:30, which was a lot better as it meant we could run many more devices, such as the washing machine or dishwasher etc.
What does the Octopus energy electricity data say?
One of the advantages of using Octopus Energy is that they supply customers with daily energy usage data. One can go onto their website and download a year or more data, which I found very useful.
I was able to use the data to understand how much electricity we use on a daily, weekly, and monthly basis. More importantly, I could work out that, on average, we used 14kWh during the peak period of the day.
I built a chart from the data to show me exactly what our energy would be costing us in the future based on a few basic assumptions, and the results were quite scary. ?
Using all the calculations from above and the peak and off-peak usage, we have the following chart for the year:
The chart above shows the following:
- Dec 2021 to Jul 2022, we were on the Octopus Go tariff, and the price of electricity was affordable.
- Aug & Sep 2022, we were on the Flexible Octopus tariff, which was ridiculously expensive for both peak and off-peak.
- Oct 2022, we switched to the Octopus Go Faster tariff, which reduced our off-peak, but the peak price was still too high.
- Nov 2022, I’ll explain below.
Looking at the chart above, one can see we needed a solution for the rising cost of electricity, especially the peak tariff.
One solution is solar panels & solar battery storage, which is an excellent idea if one lives in a sunny part of the world and one’s house faces South East. Charge the house & batteries using the sun. It seems like a no-brainer. Our home sits in a West/East direction and gets a lot of sun in the summer, both the morning and afternoon, but it would mean solar panels on both sides of the property. In the short term, that would mean a lot of scaffolding, which is the installation’s pricey side, which we are not sure about aesthetically.
Another solution was solar battery storage without solar panels. This solution only works if one is on a cheap off-peak tariff or a night tariff which we are.
The idea – charge the batteries in the evening during the off-peak period and discharge them during the day. Since we were on a five-hour off-peak tariff, this made a lot more sense. We needed to cover the 14kWh used during the peak tariff.
Keep it simple silly.
I spent several weeks recording and understanding how much electricity each of the 109 appliances in our house used. I drew up a chart, switched each device on, and used the smart metre to show me how my watt or Kilowatt was used. This practical test would be super important when deciding what inverter was needed.
Several companies offer solar battery storage solutions In the UK, such as GivEnergy, PylonTech, Sonnen, Tesla & FoxESS, and each offers different battery and inverter sizes. There are a lot of possibilities, with data sheets a mile long. I could write a whole blog post on the various solutions, but in the end, it came down to a simple process. What we needed was the following:
- A modular solar battery solution that was easy to upgrade if we needed more batteries – we needed 14.4kW of battery in either one size or a few smaller batteries.
- An inverter that could charge/discharge the battery quickly & efficiently within 5 hours.
- An inverter that allowed us to use more than one heavy-duty electrical appliance at the same time. (The toaster (2.7kW) & the kettle (3.2kW)), equals 5.9kW).
- Ideally, the battery and inverter are made and supported by the same company.
- Good support from local installers & the community.
The community aspect was essential when deciding which battery and inverter to buy. Through my research, I stumbled upon many videos and blogs showing how to monitor the hardware and data from the inverter in the Home Assistant system. This is also how I discovered Home Assistant. I also frequented many forums and started getting quotes and ideas about what was popular in the UK.
I am not going to slag off the various other brands, but I will say to watch as many video reviews as you can. Get into the forums and Facebook groups and get a feel for what is not good. When hundreds of people are on Facebook complaining about their hardware, you know there are probably thousands who are happy and content! Use that to make your decision. That is the nature of social media. People like to complain!
The FoxESS battery and inverter checked all the right boxes.
Finding a local installer was the next trick, but fortunately, I found an electrician through checkatrader.com. The company was
I purchased five 2900kW FoxESS batteries, or energy cubes as they are referred to, and a 6kW FoxESS hybrid inverter. The inverter can support solar panels if we add some later. The batteries can be extended up to twenty-something kilowatts. We also added an Emergency Power Supply (EPS), which can be turned on in the event of a power failure. The inverter has a WiFi dongle, which communicates to the internet, producing data and statistics. It also allows the installer or Fox to upgrade the firmware or troubleshoot problems if they arise.
The last electricity chart tells the whole story.
In the middle of November, we had our FoxESS batteries & inverter installed. The setup has been running for over a month, and the results are excellent. Below I’ve included the data from the first half of November (no batteries) and the second half of November, when the batteries were discharged daily. What you can see is the following:
- In the second half of November, the peak cost was reduced significantly, which resulted in the total cost dropping by half.
- For the first time this year, the off-peak was higher than the peak, yet significantly cheaper than the peak cost in October.
- So far in December, we are tracking at least the following:
- Four times cheaper than the total cost of November combined.
- 4.5 times cheaper than October.
- Six times cheaper than September and August.
- The goal is to have a total cost similar to what we had between October 2021 to July 2022.
Gas Off – the next problem bill to solve.
Yes, this cost-saving solution doesn’t end with electricity. We need to find a solution to replace our reliance on gas for heating. Gas is also expensive, although cheaper than electricity at the moment. I am sure it won’t stay that way, given the government have set out plans for every household to shift from gas to electricity by 2035.
Octopus Energy – Refer a friend
Split £100 with this link for a friend who signs up for Octopus Energy.