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Uh, I was hoping the efficiency is a bit better at 3.6kW. Than what is the number at 10A granny cable? 50%? 🙂
That is just another reason to wait for the new engine.I’m charging constantly with granny cable(10A) and the efficiency is about 60%
Can someone measure the efficiency at 7kW?
This is how it looks at the car end:
As there appear to be some people watching this thread that understand this stuff, I thought I’d risk being laughed-off-the forum for my wild ideas. So here goes.
I have been routinely charging my ZOE overnight, mainly to take advantage of the off-peak electricity pricing. Throughout the winter, that made an early-morning start far less daunting; thanks to the pre-conditioning function.
Alternatively, if I charge during daylight hours, I can take advantage of the solar panels on my roof. Let’s call that free-electricity.
Now here’s the point. The max output of the solar PV set-up is 4Kw and the home-charger is rated up to 7Kw so the car will still draw off the grid (7Kw – 4Kw = 3Kw). The charge will be complete in 205 minutes (according to Renault website) yet the sun will still be shining and the surplus from my solar PV will go off into the grid to be sold to my neighbours.
If I were to connect via the (so-called) granny-cable, the car could only consume 2.4Kw, and if it’s still daylight the longer charging time (circa 700 minutes) is less of a problem. I now need to do the maths to take into account the differing day/night charges for the electricity that I buy.
Obviously, having the car on-charge at home during the day is not ideal for ‘the working-man’. Unless, of course if he or she works nights!
Am I talking out of the wrong orifice?If you can charge the whole thing from your panels with the granny cable; you’ll export 22kwh less to the grid. So the cost is effectively 22 * whatever your export per kwh is (in lost revenue). Assuming 5p export per kWh, that’s 22*5 = £1.10 less revenue.
If you charge at 7kw and 3kw comes from the grid, a full charge would consume approx 12.5kw from the grid. Assuming a day tariff of 16p/kWh, that’ll cost you 16*12.5 = £2.00. You’d export 9.5kWh less to the grid. Assuming 5p export per kWh, that’s £0.47.
If you charge overnight, you’ll consume 22kw from the grid. Assuming a night tariff of 8p/kWh, that’ll cost you 8*22 = £1.76. Exports won’t be affected.
So, assuming my tariffs and logic are correct (and charging is 100% efficient; which it’s not; including this is hurting my head right now), I think the costs are:
Granny Lead – £1.10
7kw charger when panels are generating 4kw – £2.47
7kw charger during off-peak tariff – £1.76If you factor in the inefficiencies, you’ll probably find Granny Lead increases to much closer to off-peak.
Oh, I forgot about export meters… if you don’t have an export meter and you’re on a deemed tariff, consuming any electric you generate is completely free (you’ll be paid the same exports based on your generation, regardless of how much actually went back to the grid). If that’s the case, the cost of charging during the day with the 7kw charger will come down; and then everything will be even closer!
Someone should put all this into a spreadsheet that takes into account tariff costs, whether on deemed tariff, charging efficiency, solar output, etc.! 😉
(or, and on the deemed tariff, granny cable effectively becomes “really free”, except for the normal house draw will come from the grid, but I suspect that’s negligible)
One of the reasons I’ve ordered a granny cable is so I can charge for free at the weekends from my solar panels (I don’t have an export meter).
I’ve got a Granny cable so I can charge for free when I visit hotels that dobt have charging facilities near by. Lol
I don’t know a lot about this (I don’t have panels), but seems like most people don’t have export meters (I guess they’re not cheap). So I guess for most, it truly is free – the more you can suck from your panels, the better!
I wonder if you start draining all that into a home battery pack whether they’d change their opinion of who needs an export meter? 😉
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