Many-worlds: Where does the energy come from? With regard to the theory that each time a wave function collapses the universe splits so that each possible outcome really exists - where does all the energy required to create all the new universes come from?
 A: There is no energy required to do that. Unitary evolution preserves energy precisely. The reason is the way energy is calculated in quantum theory, and if that is applied to MWI then each branch only contributes with its squared modulus branch amplitude to the total energy. This is the only consistent way to count energy in quantum theory.
A: There is no need for extra energy. The energy of all-worlds-together is conserved, and the energy within each-world is conserved on-average (which is what energy-conservation means in quantum theory). 
Consider a collection of identical quantum systems, where each can be in two states - we can mark the states as state $|1\rangle$ and state $|2\rangle$. Each state may have its own energy associated with it, $E_1$ and $E_2$. 
As part of the way quantum mechanics is built up mathematically, this means that each system can also be in a "superposition" state, i.e. a weighted sum like $\sqrt{\frac{1}{3}} |1\rangle+\sqrt{\frac{2}{3}}|2\rangle$. Let us consider the systems to initially all be in this state.
Now, some device comes along and measures the system's energy. What happens?
First, consider things from the standard, no-multiple-world, (Copenhagen) interpretation.  On this view the systems will "collapse" to state $|1\rangle$ with energy $E_1$ 1/3 of the time, and to state $|2\rangle$ with energy $E_2$ 2/3 of the time. So on average we will receive that this kind of system has energy $1/3 E_1 + 2/3 E_2$. And this is the same amount of energy the system "had" before we measured it (e.g. it would cost us this amount of energy to prepare these systems). So there is a "conservation of energy" in the sense that on average energy is conserved. This is how conservation of energy works in QM.
Now, let us consider the measurement from the many-worlds-interpretation. Consider a single system in the above superposition state. In this case you get that reality "splits" into infinitely many worlds, so that 1/3 of them include the system in state $|1\rangle$ with energy $E_1$ and 2/3 in state $|2\rangle$ and energy $E_2$. So if we repeat this experiment again and again (measuring the whole collection of systems we considered under Copenhagen), we will again receive that on average energy is conserved. 
And as a bonus, if we consider the whole collection of worlds from the many-worlds-interpretation, then it has the same energy as that average. 
So if you take just one system in a superposition, you will find that in each world it has a different energy (what scientists call "quantum fluctuations") but that on average the system has the same energy it initially had, and you will also find that the total collection of worlds is still in this superposition state (there is no collapse) and hence still has the same initial energy.
