HomePlug adapters should be connected directly into a wall outlet. If that is not an option, it is possible to plug the HomePlug into a power strip provided the power strip has no integrated surge suppressor. Most power strips designed for computers have integrated surge suppressors, so they are not suitable. Uninterruptible power supplies or power strips connected to uninterruptible power supplies are also not suitable.
Low-cost power strips are available at local hardware stores and generally work fine. Non-surge suppressed power strips may be referred to as "relocatable power taps". "Multi outlet taps" are also generally suitable. Extension cords may be used, but keep in mind that the length of the extension cord must be factored into the distance between the eGauge and HomePlug (40ft of wire run + 25ft of extension cord = 65ft between the eGauge and HomePlug). Maximum effective communication distance is approximately 100ft.