You only need the RFM69Pi if you’re receiving radio messages from an emonTx or an emonTH. The RPi will use its built-in WiFi to connect to your router.
You don’t mention whether you have PV - if you do, remember that the pulse LED won’t work when you’re exporting.
And of course you need power for your Pi.
Or, you could buy the emonPi parts minus the Raspberry Pi itself. I’m not sure what you’d need to order, you should contact [email protected] for the details.
That you give you a voltage input and two inputs for current transformers, and the ability to plug in the pulse and with an extender socket strip, temperature sensors.
PhotoVoltaic - your own electricity generated from light, using an array of panels on the roof. (The same consideration applies for any generation you might have - some have wind turbines, some have water wheels, some have CHP - Combined Heat & Power! But PV is the commonest.)
It wasn’t entirely clear from your question what you want to do. If it’s just to have a minute-by-minute account of your electricity consumption as recorded by your energy supplier’s meter, then that’s all you need. But if you’re thinking of doing more than that in the future, then, though I don’t think it will impact your choice now, it might pay to mention it now.
Firstly, you probably want to measure the power you are using and possibly measure some temperatures. There are several ways of doing this. You could get an EmonTX and either use a CT (clamps round one of the big cables in the meter cupboard) or a pulse counter which counts the red light that flashes.
If you want to measure temperature you can connect a sensor to the EmonTX or get an EmonTH if you want temperatures from further away.
You then want to record this data and you can do this in a couple of ways. Both use the software - EmonCMS. One is a local solution (the SD image you mention) often on something like a RaspberryPi and the other is the hosted solution emoncms.org (or both!).
The RFM69Pi is a board the plugs onto an RPi and enables 433Mhz communication between the EmonTX (or EmonTH) and the RPi.
The EmonPi is an all in one solution that will collect the data and process the data - all of the above in one package.