simultaneous equations ... such fun!

With the help of sly_dog_jonah from the MSE Solar PV forum, I've worked through some simultaneous equations to solve the question of how much Ovo and E.ON owe us, using a few reasonable assumptions.

The main one is that our total electricity consumption since we installed the solar panels has not changed dramatically, either up or down.

Using that basis, the figures from the Generation Meter and the Import Meter (which actually adds the incoming and exported electricity figures together) I've come up with the average figures for the 9 months we've had the solar panels, as well as the 3 months under E.ON and the 6 months under Ovo.

Basically under E.ON we were overcharged by an average of 3.440 kWh units of electricity usage per day.

Under Ovo we're still being charged for an extra 7.925 kWh units per day.

This is a total of around £200 for the 9 months.  We are still waiting for a 2nd offer from Ovo (they offered 6 units per day for the 6 months they've supplied us).

What is also interesting is that it shows how much benefit we've been getting from the panels in terms of electricity we've generated & used without having to import and pay for it from the grid.

For the 9 months (Winter, Spring & Summer) our electricity import has reduced by more than 25% - a saving of around £125 for the 3 quarters of the year.

So together with the income from the Feed-in-Tarrif payments, the benefit in the first year could reach £2000, and that's without making any major changes to our electricity usage.