As we approached the final stages of our build in the spring of 2020, we had to cut our Solar PV plans to stay within budget. Roll on 3 years and we now have panels on the roof and a battery in the garage.
We considered another south facing ground mount system, like we had at our previous house, but in the end settled for a system on our roof. The Solarwatt glass/glass panels are on the east and west facing roof at the rear of the house, above the garage.
The myenergi libbi Battery
The final piece of the jigsaw for our all-electric house was a domestic battery. Solar is great, but if you end up exporting most of the energy your system produces then it will be less useful. The libbi battery provides somewhere to store it until you are ready to use it.
The myenergi libbi is a solar inverter and battery storage system all in one. Its biggest advantage is integrating everything in the myenergi ecosystem (Zappi and Eddi) all under the control of a single app.
Battery modules come in 5 kWh packs (4.6 kWh usable) and you can install 1,2,3 or 4 packs for 5 to 20 kWh depending on your needs and budget. Prices start around £5,500 for the inverter, controller and a 5 kWh battery.
On the brightest days in June, the system was able to power the house in idle mode, whilst at the same time filling our 10 kWh battery by around 2:30pm. The rest of the day’s spare generation can be used with the brilliant myenergi Zappi to charge the car.
In the dark months the battery can be used to move some of our energy purchasing to the cheaper night rate (currently 15p / kWh for us) instead of during the day (currently 35p / kWh). You can setup your tariff details in the app to allow the system to charge from the grid at the cheapest times.
First Month Comparison
In the first full month the system was operating (June 2023) it generated 604.5 kWh. We had a self consumption rate of 86%, exporting 83 kWh. Here are the figures for comparison to last year;
Day Rate – 655 kWh (63.7%)
Night Rate – 373 kWh (36.3%)
Total – 1,028 kWh (100%)
Day Rate – 94 kWh (26.1%)
Night Rate – 266 kWh (73.9%)
Total – 360 kWh (100%)
Our total monthly energy use has fallen a little (14% from last June). This June was a particularly sunny month the Solar system helped us reduce the energy we pulled from the grid by 65% overall. The day / night ratio was reversed too, seeing nearly three quarters of that import at the much cheaper night rate.
In terms of money, 2022 (using todays prices) would see a bill of £285.98. June 2023 actually has a net cost to us £61.32 (including the income from our export). That’s a saving of around £225 in month one, although this will also probably be the best month of the year in terms of solar generation.
A big upgrade I’d like to see would be some form of automation so the system would decide how much, if any, energy is required to be purchased by the battery overnight, by predicting the solar radiation for the coming day.
In terms of energy, Last year we used 15MWh which is an average of 41 kWh per day and we aim to reduce that this year with the solar generation, although it was installed in late May so we missed out on the spring sunshine this year.
The battery will continue to allow us to move more of our usage onto the night tariff, time shifting some more of the heat pump use. While 10 kWh is not a lot when it comes to space heating in winter, and there are much larger solar and storage systems around, we are very pleased with the myenergi libbi and we still have the option to add another 10 kWh to this system in the future.