If you have good wifi coverage in the garage and can get away with using one emonTx (depending on where the meter is and the cabling between the meter, the inverter and the consumer unit in the kitchen) you could forget using the rfm69pi and connect the emonTx to the emonBase (Pi) via serial, this would remove any chance of “dropped rfm packets”, make the FW in the emonTx accessible for update without a programmer and potentially improve the accuracy slightly as the AC:AC would no longer need to power the emonTx (resulting in a better Vac waveform) as it would source it’s power from the Pi.
This would be cheaper, more reliable, more accurate and easier to maintain/update.
At some point in the future there may also be a FW revision available to make the then redundant RFM components in the emonTx work as a base station so you can add further devices eg an emonTH etc (see 4 CT emonBase using emonTx and Pi Zero W - #12 by TrystanLea) effectively making your P13 and the new emonTx a 4ct emonPi (even if you are only using 2ct’s)