Charging station- fills energy crystals (any type of 'battery' will do) from my solar array.
A filter pulls full crystals out, and dumps them in a relay.
-A retriever pulls empty crystals back into the charging station.
The actual "energy grid" is a length of pneumatic tube connecting the charging station to my machines
Most the machines have a slot in them to accept batteries (accessed from bottom face), or you can unload into a MFE/Batbox ect.
(personally I used energy crystals and MFEs- any type would work.)
This was back in Tekkit 1.2.5, you could use tesseracts/enderchests or AE or similar for distribution. Its basically Charging station->item transport->Discharging station/machine.
Edit- with AE and tesseracts/enderchests- you can instantly transport power over an infinite distance or across dimensions without energy loss