OpenEnergyMonitor Community

EmonPi for solar PV diversion

Hello from the USA. I currently use an OpenEVSE to charge my EV. I understand it has the capability to continuously adjust amperage to divert excess solar PV production into my EV. The OpenEVSE manufacturer tells me that I need an EmonPi to measure the solar production and compare it to my house consumption. It’s fairly clear to me how it would use an ammeter to measure solar production, but it’s not clear to me how it would measure house consumption. Has anyone made a video showing a full installation?

Also, I have 2 separate PV arrays served by 2 SMA Sunny Boy string inverters. Can the EmonPi monitor both sources of production simultaneously?

Welcome, Tim, to the OEM forum.

Can I point you towards the ‘Learn’ section here and particularly to Learn→Electricity Monitoring→AC Power Theory→Use in North America→Use in North America

The emonPi was designed for the UK domestic system as that page explains, so to measure both legs of your supply and two PV arrays - given that you’re thinking of using c.t’s - it’s probable that you’ll need a bit more than an emonPi.

You could use an emonPi. The principle is you measure the nett power flowing in your service entrance wires, the power from your inverters and then do the maths to determine what your house uses. The c.t’s on the SEWs can be paralleled to use one of the two inputs on the emonPi, likewise you could feed the infeeds from the two inverters though a third c.t. and use the second input for that.

But our experience is most people want a lot more data than that would give them.

If your inverters can accept a data bus connection (Ethernet, Modbus, etc) then you can feed that digitally into the emonPi, meaning you can use both c.t. inputs for the SEWs.

If you can’t get the data from your inverters and you need to measure their power, then - assuming they’re 240 V connected to both legs and no neutral (or it’s only the control electronics), and they feed into your load centre, then you could have an emonTx (with 4 inputs - 2 on the SEWs and one for each inverter) plus an emonBase to handle the data.

Or if you need to measure more things separately, you can mix and match the emonPi with one or more emonTx.

1 Like