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Yes. And no. You can only have the amount your incoming fuse is rated for. And I’ve not seen one rated at more than 100A on a single phase supply. More may be possible, but I’ve never come across one.

Of that 100A you can take up to 32A for the 7.4kW charger. If you add a second charger on the same 100A main fuse, you will have two chargers running at 3.6kW, which is better than nothing, but not a great advance on the 2.4kW most granny chargers give you.

I was faced with exactly this scenario at home (also my office) and I paid a little over £2000 to have the electricity supply upgraded to 3-phase and I then had a dual Type2 Pod-Point 3-phase pedestal charger installed (£1299+VAT after all applicable grants were applied), so each car charges at 11kW. If we had a car that could charge at 22kW then in theory if we only plugged in one car it would charge at the full 22kW rate.

You can see this in action on the Pod-Points installed at Tesco’s stores where one car plugged in gets about 6.5-7kW but when a second car is plugged in to the other side of the charger, both cars drop to 3.6kW charging rate.

If you can get a main fuse bigger than 100A on a single phase then this doesn’t apply, obviously.
 

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No, I said you would end up with two chargers running at 3.6kW because that's what they do. I've seen it. The software on almost all smart chargers will only allow the charger to use as much current as the supply will allow. Two Pod-points will drop to 3.6kW, two Rolecs will drop to 3.6kW. I've not seen a pair of chargers that don't do this. You definitely don't need a Zappi to do it.
 

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What else do you have running on electric in your house, the heating?

I have a 100amp fuse and two 32amp charge points that both charge at the same time.
That's only 64amps so there's still 36amps left for the rest of the house.

The Zappi monitors the overall load of the house and will reduce the current going to the cars to keep within the limit of the fuse.

You could have installed a zappi and not upgraded to a 3 phase supply.
Well, no. You obviously missed the bit about my home also being our office. So we have a lot more light running permanently that the Health & Safety people say we have to have for a minimum illumination level. We have about 4kW of servers and anything up to 8 PCs running at any time. And that lot has a split air conditioning system to cool it which uses a fair bit of power. And then there's the Everhot 150 in the kitchen. So we really couldn't have had another 32A charger on the same circuit. And a single phase would never have given us 2 x 11kW charging. And if you get the commercial Pod-Point you get a whole suite of software with it to very finely control access and charging. So your Zappi, however wonderful it might be in your home, it wouldn't have worked out for us.
 

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One 7kW charger will need 30A; two would need 60A. If your property has a 100A supply that would still leave 40A (around 10kW) available for other uses. Very few houses actually use 10kW at any instant and if you were wanting to do your charging between (say) MN & 6am you might even be able to run 3 chargers (90A) at once with the remaining 10A being enough for a small background load.
Your commitment to an aggressive diversity calculation does you credit, but your home won’t meet any kind of wiring regulations if you specify it like that.

If you look at the fuses in your consumer unit they look massive. And yet they still trip and even blow completely on occasion.

Every circuit in your home has a specification set out in the current version of the wiring regulations and the EVSE installers have to comply with the latest version on any work they do irrespective of when the property was constructed.

So if you have a gas boiler and a gas cooker your 32A cooker circuit probably looks like massive overkill but if you have an electric hob and an electric oven when you cook Christmas dinner with it all switched on, you may actually exceed the rating in the circuit while you heat the oven(s) up.

And let’s hope you don‘t live anywhere with an electric shower. Or night storage heaters!

There is some allowance for the fact that everything isn’t switched on at once (diversity in demand calculation) but the required specifications are still massively over what you’d think you actually use. That’s why you have a 60A fuse in the first place. Because you might turn everything on at once.

There is zero diversity allowed on an EVSE and any installer will look at your 60A circuit and just say no. No install possible. Even on an 80A circuit they might limit you to 16A or 30A rather than the full 32A. Andersen will not allow one of their authorised installers to install an Andersen EVSE on a circuit fused at less than 100A.

So while you may be correct, you won’t get a qualified installer to do what you suggest. You can’t have two 7.4kW EVSEs charging on a 100A fused single phase supply. You get two sharing 7.4kW which typically means 3.6kW each.

If you install them yourself your theoretical calculations may be correct, and I hope they are because the energy required to melt a 100A fuse will be pretty spectacular to behold.

If you want to charge two cars at 7.4kW you pretty much need a 3-phase supply. At which point you can charge two cars at 11kW. Which is rather lovely.
 

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Why the reference to a 60A fuse ?

OP never mentioned having one and I was specifically considering the case where a 100A fuse was fitted

I was assuming that each EVSE would be wired back to its own 30A (more likely 32A) fuse and indeed that you'd never want to run them when there was any chance of using other high current devices.
It’s a simple example of how the current wiring regulations prohibit doing what you suggest even though, according to your calculation, you have capacity for it. According to you, you could run two 30A EVSEs on a 60A supply and 3 on a 100A fused supply. You just can’t. The wiring regulations don‘t allow it. Even with an 80A incoming fused supply the DNO may choose not to allow the installation unless the diversity has been calculated and the installer can justify it to them.

Even with a 100A fused incoming supply you only just have capacity for one 32A fused EVSE because the competent electrical installer cannot apply any amount of diversity discount on that supply. This also applies to anything on a cooking, heating or shower circuit.

And as for being able to control what loads are present in your home, the wiring regulations don’t give you that opportunity.
 

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Here it is common for main fuses to be 60A or even 40A and ours used to be 40A before the whole shebang was upgraded a few years ago. We installed an electric shower and the bloke that did it fitted a shower priority box that stopped the risk of the fuse blowing if we used the shower. These shower boxes were common here and they work just as well with electric car chargers I have been told.

I cannot see any problem with just having to manage the load like this as it has been shown here to be safe as the things have been around at least 20 years and I have never heard of them causing any problem. The way ours used to work was that it either supplied electricity to the shower or it supplied electricity to the stove but not both at once and if the shower was being used the cooker was dead and would not come back on until the shower was turned off. That shower used more electricity than a charger I am sure and as most people charge at night when they are not likely to be using the stove at the same time so it would not even be something that was noticed.
Obviously this is an international forum and the UK has regulations that prohibit some things which are allowed in other countries. The fact that the electrical regulations have to be applied to buildings and installations that pre-date them and electricians effectively have an incentive to upgrade older electrical installations means that cheaper, simpler, but equally safe and effective options are not available in the UK.

The UK also suffers from having a national grid to dwellings based on a single-phase supply. Other countries (especially where people tend to build their own home) or that have poor mains gas provision often have 3-phase power supplies in their homes already because if you’re running an 8.5kW or 11kW shower at the same time as you’re boiling a 3kW kettle and a 1.5kW toaster and a 2kW hair dryer and you’ve got a few lights on, then you’ll easily exceed the fused supply on a building.

And if you have storage heating then those heaters will be warming at 16A each just when everyone says they want to charge their cars.

And actually, many EVSEs sold have current management built-in. Certainly Pod-Point have a clamp on the supply and will throttle the charger back if it detects high load in the house.
 
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