Hi Victoria, yes I remember your case now, the very high kWh consumption of electricity in your flat. There is definitely something wrong and you have taken the right route to solve the problem. Good luck with getting SP to admit a problem and finding a solution. Your earlier comment that SP could not fit a check meter I still find evasive and amazing.
Thanks for posting that, very erratic and unbelievable but I suppose it is from the App? The App is often reported with strange readings. Your only true measure of cost is from your bills, any other extract or summary is liable to have errors.
The belt and braces way to check costs is to take a known actual reading, say 18 November = 2498, and the latest say 1 Feb = 4020. They must be actuals not estimates. Take the two readings away from each other = 1522 kWh. Multiply by your tariff rate, say 15p/unit = £228.30. Add standing charge 75 days at say 25p = £18.75. Total cost is £247.05. You would of course use the actual standing charge and kwh rate from your bill or tariff terms.
This is the calculation SP do to make up your bill. The App has clearly gone wrong and for the time being cannot be used.
Ah, problem solved, smart meters do not mix with solar panels. The meters were recording faithfully but adding the solar power instead of subtracting it, its a common error.