Can you run an all electric house for free?

Solarchaser

A little over a year ago I was paying £110 / month for electricity, which doesn't sound alot for a 3 bed semi family of 5, but i had already invested in quite a few ways to cut the annual cost. 
I had a large solar array already installed and a large battery bank taking charge from the solar to reduce annual costs as much as possible.

No heat pump as the wife says NO.

I was already using batteries on Intelligent octopus to charge at 7p overnight in the winter, and heating water tanks overnight to produce heating and hot water.
Already had electric car(s)

I had already improved insulation in the loft and below the house.

My thought was to reduce import as much as possible, so as to lower costs, however after reviewing costs, it looked like I was going to have to increase my monthly payment as my annual import was up to £1470 and 16000Kwh

I read on here that Octopus would pay 15p for every Kwh you exported, and that set my mind running.
I fudged some calculations and done some man maths and decided to give it a go.
I'm on a 2014 FIT rate, so I had to give up my deemed 50% export payment (but not the generation payment) which would have gotten me around £106 this year

So instead of charging from the sun and reducing export, i instead went to never charging from the sun and actively trying to export all the solar i generated.

I bought a total of 29053Kwh.
Of that 4812Kwh was used to charge two electric cars, the rest was house consumption. 

My bill for the year was £137 including the car charging.
Without the car charging it would have been -£200 (but id have had to pay petrol or diesel obviously)


I've done this by exporting all of my excess solar power instead of using it to charge batteries as i had done for the previous 6 years,  and then charging batteries overnight and setting them to export between 4pm and 8pm each evening.
I export at this time for 2 reasons which are kind of the same reason.
1. The grid is dirtiest at this time due to everyone making dinners.
2. We make dinners between these times.

This export has offset the cost of the import.
Total export was 13256Kwh at 15p/Kwh

I continued to pay the £110 /month to octopus and so i now have £1500+ sitting in the account, some of that is from the free hours charging that octopus does now and then and recommending friends, so I didnt think the money in account was the best way to explain it really, but i thought it warranted mentioning that this money has been "saved up" during the year.
The figures I've used are straight from the top lines of the bills each month, so not removing the free hours octopus gives from time ro time as I didnt want to muddy the waters. They wouldn't make much difference anyway in the grand scheme of things, but I felt it better to be conservative with figures.

So short version is i used to self consume as much as possible and used 16000Kwh, I now export as much as possible, and deliberately fill batteries to max every night, so now I buy 29000Kwh and export 13000Kwh, and that 13000Kwh is enough to offset nearly all of my import.

Last year my off peak to peak buying ratio was 98.7%.
This year my off peak to peak buying ratio is 99.5%

So, can batteries save you money?
Your darn right they can, and for me, they are