I'm a little surprised the mark XII naquadah generators don't get talked about.

In relation to the alternate timeline of 'The Last Man' (SGA 4x20), the Tauri would have invented the mark XII series of naquadah generators.

Based on what we gleamed from that episode, it was strong enough to power the shields of Atlantis. But admittedly with the assistance of solar panels. Though for how long, it's hard to say considering the state of the city as it was buried in the sand 48,000 years later.

However within thirty years, the Tauri were able to create and refine a power source that could rival the Ancient's ZPM.

I always found it a bummer that future Mckay didn't leave blue prints or research data about such things for Sheppard to take back with him to the past. Would have helped with a lot of stuff moving forward.