On a server, we have a generator building. Everyone is connected to the main power grid and until we reached a decent amount of folks, we could self-sustain it. Now, as we need to expand it we don't have enough resources so i thought of charging the guys who used my power. This worked good but it was highly inaccurate. A power counter could be most useful as it is way more accurate. In conclusion: counter that counts how much EU has passed through it.