In Stargate SG-1 and Stargate Atlantis, an ancient race of humans* developed a technology called a ZPM (or Zed-PM for McKay fans out there).

These zero-point modules were capable of immense power generation: a single unit could power the faster-than-light drive of an intergalactic starship the size of a city between galaxies (among other equally breath-taking feats).

How powerful is a zero-point energy module (in modern terms)?

Or is it a Zed-PM?

Is the energy it produces even comparable to contemporary power, such as being measured in watts? Or is it another form of power altogether?

* Early episodes of SG-1 noted that "The Ancients" were the first evolution of the human form.

  • 3
    FYI, power is measured in Watts, which is a product of Amps and Volts. Sorry, the EE in me got out... Nov 18, 2011 at 4:19
  • 4
    It must be billions of jigawatts!
    – Dima
    Nov 18, 2011 at 14:33
  • Relevant: youtube.com/watch?v=SiMHTK15Pik
    – Jeff
    Nov 18, 2011 at 20:14
  • 4
    You mean it's called a ZPM, and incorrectly called a ZeePM by everyone else. Aug 14, 2014 at 14:27
  • 3
    What is the purpose of incorrectly writing out "ZedPM" and saying this is only for McKay fans? How offensively US centric. Oct 19, 2014 at 17:57

8 Answers 8


The best estimate we really have of this can be calculated using the following.

  1. In order to use the Chair found at Antarctica, a ZPM is required.
  2. In an alternate timeline in "The Road not Taken", 80% of the grid for the US is used to power the Chair.
  3. The total energy output of the US is roughly 19000 TWh. However, that's not all going at once. There are 8760 hours in a year, which means the power generation capacity, on average, is between 2-3 TW at any given time.

So, it seems that a ZPM is capable of producing at least 2-3 TW of power.

The chair seems to drain energy quite quickly. I don't know the exact time, but I guess it is around several days worth of power. Let's say 50 hours. That seems to indicate that it has about 200-300 TWhr of total energy.

So, it seems likely that a ZPM has a large amount of power considering its size, but it wouldn't replace even the US's energy consumption for very long...

More lines of evidence:

  1. Naqahdah Generators were used to power Atlantis. I seem to recall that 5 generators were used, but I can't find the quote anywhere... (see 'The Storm' - Laden tells Koyla about whats powering Atlantis)
  2. Each Naqahdah generator seems to be similar to a large Nuclear Reactor. I'm guessing therefore that the power generated per reactor to be no more than 4 GW (Based off of the capacity of the Palo Verde Nuclear Power Plant).
  3. Given 5 generators, the power is around 20 GW. That is enough to power Atlantis, but not it's shields.
  4. I'm sure if it was only a matter of putting in place a few more generators, they would gladly do it, so let's say it would take at least 10x more. That puts the power at 200 GW.
  5. Assuming there is a low stress environment, such as protecting the city against water, perhaps the requirement is somewhat less, say half. That puts the power at around 100 GW.
  6. Each ZPM was able to power Atlantis for about 3333 years. That would indicate that the total energy is around 876 TWhr.

Now, there's considerable fudge factors in the second set of equations, but they give a similar number to my rough estimates using the Chair. I'm guessing, therefore, that they are approximately correct, with the possibility that using a lower power task allows for more efficient use of the ZPM over time.

  • Just to be sure, is the few hours estimation for how quickly the chair would drain a ZPM assume that the ZPM is at full capacity to begin with?
    – Xantec
    Nov 18, 2011 at 5:53
  • I think you've misread that Wikipedia article: to me it looks like 2009 electricity production was 3962TWh, an average of 450GW. (In English a comma is a thousands separator not a decimal point. Also much energy use is not electrical, eg. hydrocarbons for transport.)
    – Richard
    Nov 18, 2011 at 8:06
  • @Richard: Good points, that's what I get for doing this too late at night... Oh well. Nov 18, 2011 at 13:49
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    I don't doubt your computations, but this seems FAR too low, unless the ZPM has some way to continually recharge (unless absolutely depleted) - 3 of these powered shields strong enough to hold back water from Atlantis for 10,000 YEARS. The writers have no sense of scale :(
    – Jeff
    Nov 18, 2011 at 14:06
  • 1
    The ZPMs used in the chair on earth were all depleted... The other chairs that were in use had been in use for many centuries for instance one that was depleted failed once they tried to power up the rest of a city attached to it but had been powering drones for centuries before that. There is also some hint that the chair the SG team powered up may not have been operating efficiently etc...
    – cb88
    Apr 23, 2018 at 14:15

It was stated several times that ZPMs could destroy a planet or a solar system. Can your estimate of a few hundred terawatts hours provide the energy necessary to destroy even 'just' a planet? No. Never mind a solar system.

In "The storm" lightning was required to power the shields, so obviously the shields are at a preset strength and only require enough power to actually activate them. Around 6 lightning strikes struck the city of Atlantis to power it. On average the voltage of a lightning strike is about 100,000,000 volts, and the average amps of current flowing is 45,000 (for hotter environments, like an alien world such as lantia) to get a power calculation we need to multiply the current by the voltage, P=VI, 100,000,000*45,000= 4.5*10^12 watts which is about 4,500,000,000,000 watts or 4.5 terawatts. Multiply by 6 lightning strikes we get (4.5*10^12)*6=2.7*10^13 which is the minimum that the shield needs. Therefore we can calculate the total capacity of a ZPM by examining the fact that the shields held back thousands of tons of water pressure for 10,000 years. Obviously, a single tsunami provides nowhere near the pressure of an ocean, so this is the minimum capacity of a ZPM when we say that three fully powered ZPMs held back the ocean for 10,000 years we can say that a single ZPM can provide 2.7*10^13 watss of power for 3,333 years, (2.7*10^13)*60*60*24*365.25*3333=2.8*10^24 joules of energy which is a minimum energy that is still inaccurate because more energy was required to hold back the ocean for 10,000 years therefore the actual value is much higher.

I hope this helps.

  • 2.8 * 1? I think you're missing something. Jul 23, 2014 at 2:09
  • I can't see anything missing. The only figure with 2.8 in it is the final energy figure which says 2.8*10^24 joules.
    – cadkls
    Aug 1, 2014 at 15:30
  • I must have misread - I thought I saw "2.8 * 1^24". Never mind :-) Aug 1, 2014 at 17:02
  • You're right about the energy scale, but you are missing something with the shield. It's not clear it has a static energy draw. It could be metastable, with minimal input power requirements to sustain it unless being destablized by outside forces. Thus it's hard to say whether the power from the lightning went almost entirely to "startup" or if a significant portion of the power went to "sustain".
    – BryKKan
    Sep 16, 2021 at 18:55

Just to throw my own $0.02 in here--you could also attempt to answer this question from a quantum theoretical standpoint. Given that Zero point energy is a "real" (read: theoretically predicted and, to some extent, experimentally supported) phenomenon, you could potentially use math and physics to put a rational upper bound on the available zero point energy.

Unfortunately for this approach, it seems that, while each 'point' in spacetime has a calculably positive zero point energy, the notion of 'point' is poorly defined--there are arbitrarily many points in any given volume of space. Based on that, the lowest maximum we can scientifically predict is infinitely high.

Ways in which this maximum could be reduced (SPOILERS):

  • Presume that space itself is quantized (something that doesn't seem to be 'on the table' for physicists in general). If this is the case than a proper scaling for 'space points' can be derived, and would put a strict upper bound on the available energy in an enclosed volume.
  • Presume that the ZPM harnesses energy from 'active' points in space; that is, matter or energy. In this view, zero point energy in a vacuum is not eligible for extraction, only zero point energy in the vicinity of hadrons, perhaps of a certain sort. If this is the case then it's the availability of context mass-energy that feeds the ZPM, either that of the ZPM itself, or that of the ZPM's environment.
  • At one point in SG:A, McKay states that the ZPM has an upper limit of energy it can extract without destabilizing spacetime within the current dimension itself (leading to the morally questionable idea of exceeding that limit in someone else's dimension instead). This provides another vector through which a theoretically infinite ZPE quantity could be limited--either if, by breaking that limit, you destabilize one or more cosmological constants to the point that the physics that separates probability manifolds ("dimensions") from one another breaks down; or if breaking that limit passes a certain 'safe energy density' yielding the same outcome.

I don't think any of the above points provides a practical way to put an upper bound on energy output; but I thought I'd put my notes down in case it spurred someone else to some better ideas.

  • 1
    "Presume that space itself is quantized (something that doesn't seem to be 'on the table' for physicists in general)." - But it is, see Planck constant
    – Izkata
    Aug 14, 2014 at 10:45
  • @Izkata This seems to indicate that action (change in velocity, energy levels, etc) are quantized, but it doesn't say anything about position. Unless you are thinking that an entity's location in space-time is quantized in response to the quantized nature of action? Sep 2, 2014 at 16:50
  • 1
    Quantum theory does suggest that a Planck volume would be a possible size of a "point". Another candidate for upper limit of energy would be the mass of a black hole of the same volume. Jan 12, 2018 at 22:16

Before we say how much energy it has, we have to make some assumptions:

  1. A single ZPM is capable of powering the star drive and shield simultaniously, allowing the city ship to escape (at least) an Earth-size planet, meaning it is capable of achieving at least 11m/s delta V, under sublight engines.

  2. The maximum capacity for powering the shield, under constant load, is 3333.3 recurring years.

  3. The ship's engines are capable of 100% electrical/kinetic energy efficiency.

Let us also assume that 100km (100000 metres) straight up is enough to reach a stable orbit.

Conservatively, assuming the city-ship comprises a mass of around 22 trillion kilograms (60x Empire state buildings), and has no mass nullification tech, would require 242 trillion newtons of force, to reach escape velocity instantly.

So, the ship would have to fly for at least 9000 seconds, with both shields and engines + essential system active.

E = (1/2 M V^2), so E = 1331 GJ per second for 9000 seconds, which is roughly 12 Million Giga Joules. This translates to approx 3.2 Billion KW, or 3.2 TeraWatts This is only for engine operation, for two and a half hours.

For shield operation, which is likely to be quite exhaustive, this would take up the bulk of power consumption, so lets assume, 4 times that, under high load conditions: 12.8 TW. Add that to our engine consumption and you have around 16Terawatts.

This also means that under low power/drain conditions, that the shield will consume 4.8Gigawatts per year, when submerged.

This is a bare minimum figure, with conservative estimates. I would imagine an electromagnetic shield capable of deflecting high speed space debris, energy weapons, and millions of tons of water for thousands of years, would consume considerably more.

On a side note, if a city-ship of that mass every crash landed like it is depicted doing twice in the series, it would likely cause an extinction event, if it's descent was uncontrolled.


On Atlantis the shield was up for about 9 seconds before it fade away So that 27 tera watts is the base amount that the zpm can hold to active the shield

  • One thing I didn't cover in my post was how much electrical energy the ZPM can deliver per second, regardless of it's (probably massive) capacity. It's possible that under very high loads, just like a conventional battery, that it simply cannot meet the instantanious energy requirements of whatever apparatus it is plugged into, causing the shield to cut out before the ZMP is physically comprimised, in the same way a battery would burst or explode if subjected to extreme loads.
    – Ian Young
    Jul 16, 2016 at 20:18

Unless the Ancient weapon platform in Antarctica is more powerful than the chair in Atlantis, we can equate "80% of the US electrical grid" to the power output of the paired MK2 generators powering that chair in Atlantis and not to a ZPM.

That's around 300 gigawatts, which is quite a lot. Given the MK2 is just a MK1 putting out 500% the power (for short times) that suggests a MK1 puts out 30GW. It's my own suspicion the MK1 was rated to about the same output as the power booster device O'Neill built to dial the Asgard. The MK1 was the eventual result of Carter's effort to reproduce the booster. This device was said to increase power to the gate 10 fold which fits if the SGC's reactor was a big 3GW model. Interesting for comparison but not a ZPM.

(It also begs the question why the SGC would ever have a 3GW reactor not to mention how a 3GW reactor wouldn't be able to dial Othala with "ten times the draw" when we see several cases of stargates running off of ~50kw energy sources like Carter's fuse box for Orlin's gate and jumper cables in "1969"...)

It seems the estimate of the energy required to overcome Earth's own gravity (AKA "BOOM") is about 10^32 joules. About ten minutes of the Sun's total output. This is useful because the ZPM Ba'al tried to booby trap was said to have enough power to destroy the planet. This may be a low estimate or it could a a few orders of magnitude high but it's the one we have.

That works out to around thirty thousand Trillion Terrawatt hours. That looks like: 30,000,000,000,000,000,000,000,000,000 Watt hours. (Per ZPM)

Or equivalent to Atlantis using about ten trillion terrawatts 24/7 for 10,000 years to keep the shield up (assuming the Ancients put fresh batteries in when they left.)

I think this estimate is too high though since Atlantis manages to burn through at least one relatively pristine ZPM in just a few episodes without blowing up their planet from the waste heat alone, because; physics.

(Obviously the real answer is "however much power the writers think they need that week" and their math isn't always very good.)


First I want to say that this is not anything I know how to cite sources for, but rather a number of educated guesses based on such episodes as when Daniel became a displaced ghost and when trans-dimensional organisms were bleeding over into our universe, both caused by a ZPM. I'm also speculating based on the nature of what a ZPM seems to be, namely a crystal, and the appearance of what must be super conductor conduit and circuitry on the exterior.

My understanding of how a ZPM works has always been that it houses an artificial singularity of the type which in Star Trek terms would be a pocket dimension or subspace bubble. The physical structure is used to regulate the power flow rate, probably by inducing a structural collapse of this bubble, kind of like getting power from a hydro-electric dam but with better control over output rate.

I imagine that power draw influences the structure of the crystal, bringing crystalline structures into alignment, with the increased power flow stimulating an accelerated rate of collapse for the bubble or singularity. I also feel it is worth noting that influences from the ZPM, including turning an entire outpost invisible by pulling them out of phase with reality, seem to rather strongly imply that this subspace bubble extends outside of the physical structure, so rather than containing it perhaps the unit serves as an anchor point as well as a capture net system for harnessing energy from it.

Now all of this would massively complicate the matter of trying to calculate energy output capability, while at the same time explaining both the discrepancies seen within the story telling and how it might be possible for such a device to destroy an entire planet should catastrophic failure ever occur.

I would also like to add that the quantum dimension notion of space-time being distorted in one dimensional reality to provide power in ours could be both why the power generation has a limit per unit as well as why waste heat is not generated. I myself prefer my Star Trek inspired concept of what a ZPM is and how it might operate, if the collapse of a subspace bubble has some aspect of inversion to how it operates relative to conventional space then this might also account for certain other aspects.

I know this does not directly address the question or how to answer it, but I am reasonably confident in my interpretation of this rather elusive technology, hopefully you will find it as interesting as I do. But it has been awhile since I watched any of this, so hopefully I'm not improperly recalling anything too important here.

I guess my final conclusion would be that yes, in terms of how power is generated and the power output type and amount, it very likely is unlike anything that we have here on Earth to compare it to.


So a ZPM can use roughly 27 TW for 9-10 seconds to activate atlantis shields, so for them to hold back that same ocean for 3,333 years would have it capable of storing 283,795,617,600TW. That would be 283 zettawatt it can store at the least and use before being useless right? Which is indeed insane, and could explain why it could destroy huge amounts of space when it explodes.

Though it could take more energy to activate the shields to start with be a huge amount, we don't know so ignore any of that stuff. Oh, it's 2am hear so yeah think this is all correct.

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