Me and David have been talking about this and that behind the scenes, mainly ZPMs and we've come up with numbers...mainly him lol.
Using various means we've come up with;
10^26 joules
10^27 joules
10^28 joules- I think is the best value, bar the planet destroying one
For a ZPMs energy.
10^28 would destroy 3/4 of the planet and obliterate Mars completely according to David. Also using those 3 figures we were able to come up with Wraith weapon yields. By dividing etc...So if the ZPM had each of these values the corresponding Wraith yield would be;
10^26 joules = 400 megatons
10^27 joules = 4 gigatons
10^28 joules = 40 gigatons
Thats using the siege fleet and assuming when Mckay said days he meant a full 7 days, it could be less than that but its doubtful its more than that.
We're also assuming a rate of fire from the fleet of 100 shots a second, which is pretty high as well.
For reference 3 days would yield;
10^26 = 936 megatons
10^27 = 9.4 gigatons
10^28 = 93.6 gigatons.
The figure of 10^28 comes from the shield holding under water for 3333 years with the water pressure.
Anyway, I just wanted the numbers down so I can find them again lol.
Using these numbers we could work out shields for Tau'ri ships too...If we felt so inclined.