How much wattage would you need to accelerate a four petaton spaceship by 1g for a year? This should be about enough to reach near light speed, which is perfect for interstellar cruising, but I'm wondering how feasible this timeframe is given that it would obviously require a lot of energy (not sure how much but it's definitely a lot), and I want to keep my antimatter generators realistic, within a few grams to a kilogram per day per generator.
I suppose, put simply, how much wattage would I need to accelerate this massive spacecraft and do I need to adjust my timeframe for reaching top speed? Or as a secondary possible solution, would it still be scientifically plausible if I increased the output of my antimatter generators further than this?
EDIT: Okay, I made a mistake in my question and said petatons instead of teratons (this ship's mass would be somewhere around 5.5e15 kg). Using this new weight and assuming it takes either 10 or 100 years to reach full speed instead of 1, how much will the power requirements be reduced? Could you use the gravity assist of large planets to reduce the power consumption any further?