We finally decided that the time was right to purchase an Electric Vehicle. Second hand prices are very low at the moment and the availability of charging points is getting better. We settled on ordering a 2020 BMW i3.
Having an EV opens up a new range of electricity tariffs available from Octopus and crunching the numbers shows some quite surprising results. Currently on Octopus Cosy and Fixed Octopus Export, I had already picked up on the fact that the cheap rate electricity price and the export price were getting very close (16p v 15p). This meant that there wasnt a great deal of financial difference whether I heated my hot water tank with excess solar via my Eddi PV diverter or did it during the cheap rate periods. One of the new tariffs I could now access with an EV is Intelligent Octopus Go. This tariff is still compatible with Octopus Fixed Export, so I could still get 15p per kWh exporting my excess solar. The idea behind this new tariff is that you hand over the control of charging your EV overnight to Octopus. You just tell them how much you want the car charged and when it needs to be done by. As a reward for this you only pay 7.5p per kWh. This price is a game changer! If I switched to this tariff, then I would obviously get very cheap electricity for my car, but it also meant that I would not get the second cheap rate period in the early afternoon that I currently have when I recharge my 5kWh house battery. Therfore if I assumed that I fully recharged my battery twice on the Cosy tariff, this would currently cost (5 x 2 x 18.13p) £1.81. If I switched to Intelligent Go this would now cost (5 x 7.5 + 5 x 30.52) £1.90. No big change. However heating my domestic hot water now becomes much more attractive during the cheap overnight period, rather than using diverted solar which could be exported instead. If I assume I use 4 kWh of hot water a day, this currently costs (4 x 15p) 60p per day in lost export. If I switched to heating it at night, it would cost (4 x 7.5p) 30p per day. This equates to about £12 per month in savings! As well as saving, I am also helping the grid stay clean by providing my green energy to them in the day when it is needed and using green energy from the grid at night when it isnt needed. So the question is, what is the point of my £500+ solar diverter now? I suppose the pricing of electricity could change in the future and it might make more sense to use my own solar again, but that seems unlikely to me. Perhaps I should look to sell it on to someone who doesnt have an EV?
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After using the Octopus Cosy tariff for a month, I could now see how charging my 5kWh battery twice a day at cheap rate, was effecting my unit cost.
Over the month, I used 2.1% of my electricity at peak rate (4-7pm, £0.42), 17.4% at mid rate (£0.26) and 80.5% at low rate (£0.16). This gave me an average unit cost of £0.18 per unit. It seems that even a small battery can have a significant effect on electricity cost and this was in addition to the extra savings I was making by utilising more of my solar panel output. |
AuthorEx Radiographer, Information Analyst, Teacher and Self-builder. Now retired Archives
December 2023
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