What powers the TARDIS?

Question

I've been rewatching Doctor Who and I recently discovered something that has confused me about the TARDIS. In the classic and new Doctor Who, the Eye of Harmony is stated to be a limitless power source. Yet, the Doctor has been seen multiple times recharging/refueling the TARDIS using something called rift energy. In other instances, the TARDIS has completely lost power due to it being in "the wrong universe". And then on other occasions, the Doctor referred to artron energy as the main power source of the TARDIS.

What exactly powers the Tardis - is it ripped energy, or time vortex energy, or the Eye of Harmony, artron energy or a combination of these?

Answer 1

http://www.whoniverse.net/tardis/tardiseye

One of the Hearts of a TARDIS (like Time Lords, a TARDIS has two) is a massive energy collector that is a mathematically constructed copy of the Prime Eye of Harmony on Gallifrey. In modern times it is often referred to as an Eye of Harmony (which can cause some confusion). Because of this, some Time Lords refer to it as Point Zero. These Eye copies can be found on all TARDISes after the Type 24. The Eye's iron-like Containment Sphere is located beneath the Cloister Room. While the Prime Eye's Containment Sphere is 10 km in diameter the TARDIS's sphere only about the size of a house.

Artron Energy created by the Prime Eye of Harmony on Gallifrey is broadcast into the Space-Time Vortex. This energy travels though the Vortex's Time Contours. Attached to a TARDIS's Containment Sphere is the Receptor Antenna, which collects artron energy using chronon transduction. The naked singularity at the Heart of a TARDIS is directly linked to the Space-Time Vortex, and uses Chronon Transduction to collect the energy.

...

Without the Prime Eye of Harmony a TARDIS would eventually have to refuel itself. A TARDIS can travel at least 22 billion years before refuelling. When necessary, the Eye's Receptor Antenna is also capable of collecting temporal energy from temporal instabilities, fault-lines running between dimensions, scars on reality, or rifts in time and space that found throughout this Universe. Time Rifts make the best fuel source. Such a rift occurs when two or more dimensions are pressed against each other creating a rift or a scar like an earthquake fault line. The TARDIS can drain off the energy created by the competing forces. Depending on the current energy level of the rift it can take a few minutes to a few days for the TARDIS to power up completely. The rift energy collected by the copy Eye is processed into Artron Energy to make it usable by the Transpower System. This energy is stored in the TARDIS's other Heart (aka Main Space-Time Element) located in the Console. A TARDIS's Emergency Procedures will automatically try to divert any large explosion or energy release that occurs inside the TARDIS into its Eye of Harmony.

Answer 2

We've seen contradictions from the TV movie on. In the original series, TARDISae are powered via energy beamed from the Eye of Harmony on Gallifrey. In the TV movie, the Eye appeared to be housed in the TARDIS itself. in the early seasons of the new seasons, it wavered a bit - Gallifrey was gone, or at least inaccessible, trapped in the time lock, so the TARDIS needed to use rift energy to refuel. The jump to Pete's World severed any possible connection to the Eye of Harmony, so the ship lost all power. The Doctor found a sole active node and literally gave it the breath of life, giving "about ten years of [his] life" to it (presumably regenerative energy, the first time we've seen it shared like that)

In Journey to the Centre of the TARDIS, we see that the Eye of Harmony is back inside the TARDIS itself again.

Now in both this case, and in the TV movie, we could be looking at another example of trans-dimensional mechanics, and in fact the Eye of Harmony IS on Gallifrey...and at the same time, inside not only The Doctor's TARDIS, but ALL TARDISae.