So - I’m using slightly skewed data, as Im going to get batteries and my EV at the same time, and I’m lumping in all my savings together - so the figures may not be replicated elsewhere for others.
Basically - at the moment, we’re paying £475 a month for our ICE vehicle (all finance, car tax, Mot, insurance fuel etc etc) when we switch to MG, we will be paying about £375 for the equivalent- basically the car costs more, but the fuel costs a lot less!
So - already we have a ‘saving’ of £1200 a year.
The battery storage using octopus go to charge up overnight, will take our average cost per KWH down to about 8-9p as opposed to the roughly 22p we pay now. I’ve done some back of fag paper calculations using octopus compare - but roughly average savings (at todays prices and our usage - approx 3000kwh - not including car charging) will be between 450-550 in the first year. If the day rate goes up over the course of the next year (which it already has) the savings made will be greater.
So - that’s about £1700 ‘saved’ in the first year, if you apply the logic that day rate will increase year on year - it might be a larger saving if £1800 in year 2 & maybe £1900 in year 3.
Currently looking at a Givenergy system 8.2kwh, 3.0 kw inverter and total cost inclusive of fitting should be circa £5000 - that’s purchasing batteries myself and getting my standard sparky to fit the batteries (he is a qualified Givenergy installer - or will be very soon!). So…roughly payback time of 2.5 years as we stand now.
BUT. If you look at it from another point of view - ie. If you were to invest £5000 in a bank account what would your return be in 3 or even 4 years? Even at 3% you’d be looking at about £400 in 3 years and £600 in 4. With a battery system, I’ll be looking at saving maybe £850 in year 3, or say £2750 in year 4, so theoretically a better ROI.
Obviously I’m not a financial advisor and this is just my calculations based on my findings - I’m not saying I’m 100% right, but I’m pretty sure I’m not wrong - If I am, I’m more than happy to be proven wrong so I don’t make a mistake

but I’m pretty confident in my figures. Obviously my figures are taking into account savings based on a car and battery system simultaneously- obviously with just a battery system, the payback period would be longer - but again, is it better than money earning interest in the bank (if you look at it in terms of a Laing term investment?).
Obviously you also need to be on a cheap night time tariff for this to work with my figures, such as octopus go/intelligent or EDF go electric. Theoretically they could take this type of tariff away, but I can’t see that happening as electric is cheap at night - I think worst case scenario Is that it just gets more expensive at night, but still cheaper than the standard day tariff.
Anyone who has stuck with this post and is still reading and If you’re not on a time of day tariff such as octopus go, and you’re thinking of switching, you can always use my referral code below (or you could use anyone else’s instead) and that’ll give you (& me) £50 credit to your bill. It’ll also help people who are on a variable with another supplier during this cost of living crisis as everyone is charging the same amount if you’re on a variable and this will save you £50 on your bill. You can switch to octopus and ask to be put on the variable. At the moment you can only switch on the phone, and my referral code is gray-fern-7875 - obviously what you can do in the future when you are a customer, is refer your family and friends, save them £50 off their bill and you save £50 for each too - so you could basically get a year free energy.
But in the future I’m sure you’ll be able to switch by clicking this link:
Octopus customers pay less: Cheaper than price-cap prices, rewards for using less when the grid is stressed, and smart tariff savings for your home, car or battery
share.octopus.energy
Obviously I’m not a financial advisor, so don’t take my advice as gospel, but it’s the way that I’m going to proceed and hopefully I’m right!!