I thought I’d put this chart up here, from yesterday.
I’m currently on the Octopus Flux tariff, which is designed specifically for households with solar panels and battery to maximise their electricity export income and reduce import from the grid. I only switched from the standard tariff (combined with the Outgoing Octopus tariff for exporting) recently, mainly because it took me a while to work out how to charge the battery from the grid.
Octopus Flux is a smart tariff – it makes use of smart meter readings to offer variable pricing. It has a 3-hour cheap rate period at night and a 3-hour peak rate period between 4-7 pm, when the demand on the grid is highest. The idea is to fill up the battery during the night when the grid electricity is cheap, and export power during the peak period when you get paid extra for it.
Now, back to the chart at the top. On October 3, the solar PV produced 12.5 kWh while we consumed 15.4 kWh, of which 10.8 kWh came from the solar PV and 4.6 kWh from the grid. Most of that grid-power consumption took place during the overnight cheap-rate period when the battery was charged. The fully charged battery and the solar panels helped to minimise grid-power consumption outside the cheap-rate period and we were able to avoid drawing power from the grid at peak rate without changing our routine, like cooking, boiling the kettle and watching TV. I also set my battery to export some of the battery-stored power to the grid during the peak hours, so I actually earned a bit of extra money for helping out the grid a little (by 1.7 kWh) at its time of need.
What does this all mean? It means that I’ve used the battery for load-shifting – moving most of our grid-power consumption away from the peak period (charged at 33.27p/kWh) to the cheap period (14.25p/kWh). Of course the solar panels save a lot of money, but October is when the PV savings start to decline rapidly as days shorten. The battery combined with a variable tariff adds extra savings during the darker time of the year.
Related read: Unlocking Home Efficiency: The Value of Multiple Technologies