The eGauge2 requires a HomePlug (PLC) adapter that uses the HomePlug 1.0 standard. Adapters that use the HomePlug AV standard (such as the TP-Link TL-PA2010) will not work with the eGauge2. eGauge Systems no longer stocks HomePlug 1.0 adapters, so they must be sourced through a third party.
In general, any HomePlug 1.0-compliant adapter should work with the eGauge2. You will only need a single HomePlug 1.0 adapter, however it may be beneficial to purchase multiple adapters if available as HomePlug 1.0 adapters are becoming harder to find. As a general rule, adapters with a speed of 85Mbps or lower are generally HomePlug 1.0, while adapters with a speed of 200Mbps or higher are generally HomePlug AV. If you have questions about a particular adapter, eGauge Support may be able to assist with verifying whether the adapter will function as expected.
eGauge does not offer any sort of warranty on HomePlug 1.0 adapters sourced through third parties. Limited technical support is available. If necessary, eGauge2 devices can be replaced with a newer eGauge meter - any data can be copied from the original eGauge2 and copied over to the replacement. The same CTs can be used. Contact eGauge technical support for additional information.