Economic case for home EVSE installation

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nealchampion

Member
Joined
Nov 9, 2023
Messages
11
I bought our 2017 Leaf (30kwh) in November last year, and am generally really pleased with it.

I've just been charging it with the type 1 charger that I plug in to an ordinary 3-pin wall plug (I'm in the Isle of Man, which uses UK electrical standards). This provides 13A/240 volts, but still charges the battery at 8~10% an hour (aside: battery indicator is on 11 bars, and my calcs based on data from LeafSpy makes me think the battery is at about 27.5 kwh now).

I've now got enough data on usage, charging, costs, etc to try and calculate whether it's worth getting a Type 2 (Mode 3) EVSE point installed. These have to be done by a registered professional here, and cannot be had for less than ~£1000. The plus side is that once installed I can use a reduced overnight electricity tariff, at 19p/kWh compared to normal tariff of 28.5p/kWh (we can't get the overnight tariff/supply enabled until the electricity company inspects the installation). But the payback time is still very long, I think. Here's my working:
- miles/month: ~500
- efficiency: 3.7 miles/kWh (there's lots of hills here)
- therefore, kWh/month: 135

The cost using the daytime tariff is £38~£40/month. Using the overnight tariff would save ~£15/month, but there's a lot of £15/month to recoup the £1000 EVSE installation cost! (5 and a half years, to be precise)

Can someone check my working, and point out if I'm missing anything, please?

Thanks in advance
 
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Even if you are a business, I would not recommend installing a "Type 3 (Level 3)?" EVSE. Especially with such a small battery pack, a decent Level 2 EVSE (~40-50 kW) should be sufficient.
Oops, my mistake - I meant Type 2, Mode 3 - I've corrected the original post now
 
The only difference would be the possibility to charge at 6kW instead of 3kW, and that depends upon the power rating of your OBC.

The higher rate will cause higher thermal stresses throughout the system (OBC, cells).

If you need the higher rate in order to meet your daily commute then so be it, but otherwise it seems too costly and low rate of return (payback time), risk vs benefits, etc.

i suppose that a special meter is required to keep track of daytime vs nighttime usage in order to bill for each. Maybe such a meter can be added and you could get the night rate using the Level 1 (Mode 2) as is? Or maybe that is only for a dedicated circuit and doesn't apply to whole house usage.
 
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The only difference would be the possibility to charge at 6kW instead of 3kW, and that depends upon the power rating of your OBC.

The higher rate will cause higher thermal stresses throughout the system (OBC, cells).

If you need the higher rate in order to meet your daily commute then so be it, but otherwise it seems too costly and low rate of return (payback time), risk vs benefits, etc.

i suppose that a special meter is required to keep track of daytime vs nighttime usage in order to bill for each. Maybe such a meter can be added and you could get the night rate using the Level 1 (Mode 2) as is? Or maybe that is only for a dedicated circuit and doesn't apply to whole house usage.
There's the rub - my Leaf only has the 3kW OBC, so there's no speed advantage to be gained from having a more powerful EVSE.

Your last point is valid. To have the off-peak tariff, the electricity company does fit a dual meter. I should find out if I can get that anyway (I could probably come up with some other believable use cases for it), and then I could run my Level 1 charger and still benefit from the cheaper overnight tariff
 
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