I like the idea of a chunkloader, as I currently don't use a mod that has one.
As for energy, if it took 32/t to load a 3x3 area and 128/t to load a 5x5 area it would take 3.6/t/chunk for the former and 5.1/t/chunk for the latter, a good progression, and very easily providable by a batbox or a MFE respectively.
As for a recipe, how about Tier 2 or so? Require at least one Advanced Machine Block, at least one energy crystal (or better), and at least one advanced circuit, therefore using plenty of iron, coal, diamond, redstone, lapis, and glowstone to drive the costs up. The energy crystal means you can drop another charged energy crystal in it to have it run, and with a transformer upgrade you could drop in a lapotron crystal. A battery probably would die too quickly (10000 EU at 32/t lasts only 15 seconds).
If the costs are high enough with materials that should discourage spamming. The alternatives are either use few of them but more energy (and likely using more diamonds with diamond cables or MFEs), or use less energy but have higher material costs (that is, diamonds). As it says in somebody's sig, balancing a game is to make it hard to decide between two choices.