Just as a quick note on the theory behind the energy systems, and why they seem to be so incompatible (at this point I really need to find a static page to link to, but I'll type it out again).
In the early days (yay! story time!), before gates, and before TE became popular, MJ and EU were fundamentally different in both use and concept.
EU generation was typically done to a storage medium (Batbox, MFE, MFSU), and power would be used on a per-operation, burst basis. When the storage block got low enough, a burst of fuel would be put in to top the storage up a bit.
MJ was intended to be generated continuously. The engines may not have major penalties for being used in a start-stop fashion, but the machines were constant-draws (quarries, farms, etc.). Used for relatively large projects where the generation was matched to the use, and it leant itself to continuous and stable systems.
The big change came when TE rose to prominence (it was around for a while, but became really popular when Gregtech began to be included in packs by default, as it added cheaper game start methods). TE changed MJ in two ways. First was the redstone energy cell, allowing MJ to be stored and moved. This meant that you could set up on-demand generation and use it for small operations, which leads me onto the second way TE changed things. It offered processing methods. The pulveriser, powered furnace and induction smelter were different to most other MJ-consuming machines in that they were intended for small operations (i.e. processing a single ore, or stack of ores). It was possible to automate them, but the philosophy behind it was small periods of activity, and long periods of idle-ness.
This lead to MJ and EU approaching the same point, and many mods began using them interchangeably (MFR, AE, etc.), but the generation remained more or less the same. most engines are still intended for constant use. The addition of gates means that things like combustion and biogas engines can stop-start, but the theory is the same.
Recent changes to BC show a return to the previous mentality. Machines lose energy over time, meaning that they become less feasible to leave running constantly. You are better off setting up a system whereby it's always running, and balancing the input and output.
So, in summary, the energies are intended to be different and separate. You are not supposed to be able to use a solar panel to power a quarry (you can, but there are losses). You are better off going out and finding an oil spout and powering it on fuel. Or setting up a boiler and powering it from there. The generation methods work in fundamentally different ways. Also, I have to say that I would like to see a nuclear reactor with similar principles to boilers (LONG startup and shutdown times, taking care of a base energy demand).