The key thing here is that this is shifting electricity usage away from the peak time period in the evening.
http://mysmartenergy.uk/Prices/Yorkshire
Shows the current electricity prices via octopus agile.
The Friday evening peak price was 82p/kwh
Those peak prices pull up the average cost of electricity for everybody.
(NB the agile prices are without the government cap I believe)
The overall energy usage looks like this.
Key thing here is that the red (imported electricity) is huge in the early morning.
The house is then powered by the battery.
(red flat lines at 0/ turquoise, which is the battery goes above 0).
The battery drains but then the yellow, which is the solar system kicks in, the battery is then trickle charged - its turquoise line goes below 0.
This means we used all of the solar generation, coupled with the early morning charging to avoid the 82p peak.
But the real issue is this:
The standard tarrif is 33p / kWh.
Which is hiding these peaks and frankly doesn't look like it can last.
Electricity prices are far far higher behind the scenes so it's best to get your own solar / battery system ASAP IMHO.
Ooh one last thing. By using the battery I've shifted the electricity usage and got £50 back from the octopus saving sessions.
Peter Adamson