HSTEd
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Obviously a granny lead would not appear in the statistics and will be adequate for many users.
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UK switching to electric vehicles discussion
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If batteries become widespread the power companies will have no need to incentivise night time use and the off peak tariffs will rise
marshlinker
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My house is 100 years old so Ive not kept up with things but the Local Authority here's car charging requirement for new builds was /is (at least until recently) a 13A socket.
That may account for marginally lower figures than I originally accounted for but a normal charger is more flexible and you can’t get a cheap overnight tariff with a granny lead. Unless you’re a particularly low mileage driver the payback period for an Ev charger is relatively short (especially if renting) so I’d imagine that for most folk if they could get a charger they would get a charger
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The legal requirement in GB is that all new builds and major renovations (with a small number of exceptions) have EV charging points if house or flat has a parking space. In England its Part S of the building regulations and came into force in Summer 2022. Wales and Scotland have virtually identical regulations. There may be a very small number of houses which had permission granted before 2022 still working their way through the system but by now this number will be tiny, as any updated/revised applications will fall under the new regulations.
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HSTEd
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Well my own company's Economy 7 tariff is only ~6p or so more expensive than the EV "Economy 5" tariff. The latter also comes with a significantly higher daytime rate, which I will ignore (nearly 10p/kWh more!).
Incidentally, their cheap EV tariff does not require a registered car charger.
Typical car mileage in the UK is about 7400 miles, at a ballpark 4 miles per kWh that's ~1850kWh per year, or £111 per year, assuming that using an EV charger is required for the 6p in electricity rate.
Even cheap EV chargers are a couple hundred pounds these days and you won't get much change out of £1000 for an install including labour, the new circuit, and all that.
If you use significant amounts of electricity during the day, this cost advantage will be shrunk by the higher electricity rates associated with EV tariffs.
Sure it's cheaper, but the rate of return on capital isn't enormous. Especially as noted, that many EV tariffs are available without car chargers.
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And as I said that may work out best if youre a low mileage user. But the cheapest economy 7 deals from all the major providers seem to be about 13p-I’m currently paying 6.6p for 6 hours. And there’s still a good chance you’ll need to install an outside socket, or run the cable out of a open window, and importantly at 3kw on a 13amp socket (or more typically limited to 10 amps/2.3kw to prevent overheating) the AC-DC losses are a much bigger factor, reducing efficiency and increasing cost per mile.
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HSTEd
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The average car will tend to use approximately 20 miles a day. A 2.5kW granny charger add 12.5kWh or 50 miles in a five hour charging window, 70 miles in seven hours.
My parents currently run equipment in the garden using a lead through the corner of their letterbox, other solutions are available I'm sure. However adding an outdoor socket will still be substantially cheaper than adding a 32A dedicated charging circuit and a government mandated 'smart' charger.
I could get 9.5p/kWh for 5 hours without an EV charger - indeed that is what you can get from Octopus for 5.5 hours on their non intelligent EV tariff. I don't currently have a car and I have a solar system which means my tariff choices are essentially driven entirely by gas unit price.
Loss will not be very different charging at 32A as 10A under British weather conditions, this is emphatically not the US where they had issues charging at 120V@15A in -30C weather.
Even if losses are marginally higher they are unlikely to be a significant cost driver.
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Losses on AC charging are typically about 500w, which is largely fixed as it not only covers heat loss but more importantly and significantly running all the power electronics in the car. In your 5 hour window you will have sent (and paid for) 11.5kwh but you will have only added 9kwh (36 miles at 4miles per kWh) into the battery. The slower you charger on AC the greater this impact is. It’s fine if you’re only doing commuting with your EV but as soon as you start to do longer trips it’ll become a hassle and more expensive.
Regardless, most folk buying an brand new EV are likely to get an EV charger as it is more practical and versatile. £500 grants are available for rental properties and quite a few manufacturers offer deals on EV chargers when purchasing cars (eg Ford, VAG, Volvo).
When I've looked I've seen people recording around 10% losses when granny charging, so around 200W. IIRC this is mostly to power the controller/electronics, so is a similar loss at 7kW charging too, but 200W / 7kW = 3%.
So granny charging means you're paying an extra 7% due to losses, have less access to tarriffs (mine shows 9.5 instead of 8.1 p/kWh, so 17% more expensive) and occassionally may need to use public charging to top up between sucessive long journeys.
Falling back to public charging is likely the largest difference!
> My parents currently run equipment in the garden using a lead through the corner of their letterbox, other solutions are available I'm sure.
When I did similar it was taking me a few minutes to set up, whereas with a dedicated charger I wouldn't need to charge as often and it'd be faster to setup.
So granny charging means you're paying an extra 7% due to losses, have less access to tarriffs (mine shows 9.5 instead of 8.1 p/kWh, so 17% more expensive) and occassionally may need to use public charging to top up between sucessive long journeys.
Falling back to public charging is likely the largest difference!
> My parents currently run equipment in the garden using a lead through the corner of their letterbox, other solutions are available I'm sure.
When I did similar it was taking me a few minutes to set up, whereas with a dedicated charger I wouldn't need to charge as often and it'd be faster to setup.