Would I really need an EV Home Charger?

Reed_Richards

I am thinking about buying an EV and wondering why I would need a Home Charger.  There's already a pair of external sockets on the outside wall of my garage so I could plug an electric car into one of those and charge at maybe 3 kW.  A Home Charger would give me 7 kW.  If I average 150 miles a week and can get a modest 3 miles per kWh that would be 50 kWh per week or roughly 7 kWh per day.  So if I use cheap overnight charging I need less than 3 hours per night to keep the car battery topped-up.  There's no benefit that I can see of charging in one hour rather than 3.  The electric cars I am looking at have a range of about 200 miles, my maximum typical journey is 100 miles so I'm never going to find myself in a situation when I need to do anything more than top-up the battery.  Home Chargers are hugely expensive and I don't see what I would be getting for the money.   

la531983

Friend of mine has a Tesla and isn't short of cash. Charges it using a normal plug in his garage. 

1961Nick

I guess it depends on whether you can make use of an EV smart tariff like Intelligent?

Expect about 10A from a granny charger - 2.35kWh

Keep_pedalling

With the amount of mileage you will be doing you can get away with using a granny charger, but as a permanent solution you should get an electrician to check the wiring on those garage sockets, drawing 10 amps for several hours the sockets can get pretty warm. If the sockets are spurred off a ring main I would get that changed for a dedicated spur. 

Reed_Richards

It seems for Octopus Intelligent you don't just need a Home Charger but the right make of Home Charger?  You get 6 hours at 7.5p per kWh.  If that's saving, say 22.5p per kWh but the Home Charger costs £1000 that would be 4444 kWh to cover the cost of the Home Charger.  So using my initial assumption of needing 50 kWh per week then it would take 89 weeks to cover a £1000 cost.  But that's only by comparison with paying the full day rate; can I not have another EV charging tariff that just goes by hours and doesn't need some wizzo Home Charger?

Martyn1981

We granny charge May-Aug, and some of Apr and Sept, to make use of PV generation. This week, shifted back to 7kW charger, simply to make life easier with a single 40-50kWh charge on cheaper E7 tariff.

In the example given of 200 mile range, that can be topped up over several days, with a 100 mile max trip, granny charging should be fine.

But as suggested, really good idea to have a dedicated circuit. Our 'garage' has a ring main for sockets inside, but an additional circuit just for the two outside sockets (one front driveway, one for garden).

There's also the other side of the discussion, which is to maximise BEV efficiency. Our 2018 28kWh IONIQ can do 130 miles, and 150 if driven gently in good weather (possibly more in ECO mode, but we use sport mode). So overnight on cheap rate we can add ~14kWh / 50% to the car.

Reed_Richards

My garage is on a dedicated spur.  The circuit breaker is 40 A.

Keep_pedalling

Reed_Richards said:

It seems for Octopus Intelligent you don't just need a Home Charger but the right make of Home Charger?  You get 6 hours at 7.5p per kWh.  If that's saving, say 22.5p per kWh but the Home Charger costs £1000 that would be 4444 kWh to cover the cost of the Home Charger.  So using my initial assumption of needing 50 kWh per week then it would take 89 weeks to cover a £1000 cost.  But that's only by comparison with paying the full day rate; can I not have another EV charging tariff that just goes by hours and doesn't need some wizzo Home Charger?

Intelligent Octopus can work with certain EVs as well but, if like me you don’t have either, then Octopus Go is the alternative option with 4 hours @ 9p pkWh.

Reed_Richards

So comparing 9p per kWh and no Home Charger with 7.5p per kWh without, then for my intended use the cost of the Home Charger would never justify the electricity cost saving.

Mr.Generous

Is there an option to charge from a 16a type socket?

If the mains board is in, or has easy access to the garage, an electrician could add a circuit with 4mm or larger cable to fit one of these, at 15a charge rate it would be 50% faster than the 10a you'd likely get from a normal socket.

subjecttocontract

When looking at charging, mileage, consumption etc, keep in mind the fact that range/consumption is reduced significantly during winter.