Coming from Schneider I would have thought they should be compliant with many standards with regards metering accuracy, they are being implemented on train stations in London where standards are extremely high. Paul Meenan Reviews the Schneider Electric Isobar P Distribution Board - YouTube. As I mentioned I’ve haven’t fitted any so am no expert by any means.
Bit more thinking on this and realised that while you can measure the PV generation and EV charging consumption in line, you’d need the SDM 120 with CT to measure overall consumption. You’d need to clip it round one of the incoming supply leads. Or is there another way?
Simon
For the main incomer, the SDM120CT with a 100:5 ESCT-T24 c.t. Is going to be the simplest way.
That was what I was thinking Robert.
Simon
I thought I ought to clarify that the YHDC 100 A : 50 mA wouldn’t do. 
Just had a skim through this thread and can provide some input. We use Modbus (RS-485) meters for industrial sites and they are cost effective, if a bit fiddly to wire and setup. Modbus also has a TCP variant, but this makes the meters more expensive and you have to deal with CAT5-6 wiring and an Ethernet switch.
Wiring. As pointed out earlier, the serial Modbus devices are connected in a daisy chain and we use Beldin 9841 or similar to connect units. Each end of a chain requires a termination resistor (120Ohm) which can often be set by a jumper. Each device is set up with a device ID [1…255]
For connectivity to a Pi. I would recommend a gateway between RS-485 and TCP/IP. Something like the Moxa device. These allow you to connect to the serial devices using the IP Address of the Gateway over port 502.
I am already using Node-Red to connect to Modbus TCP based devices to collect Solar Inverter data fror EmonCMS. Once you have the Modbus register map for the meters you are using, it would be fairly simple to populate a EmonCMS Node from this data over MQTT from Node-Red.