rationalskepticism.org

I am afraid my systems won't provide any datapoints for you as their power supplies are larger. That said, my 2080Ti (overclocked) is churning away on a WU and according to GPU-Z is drawing about 255-260W with very occasional spikes to 275W (Board Power Draw) at 95-99% TDP. Considering a stock 2080Ti is rated for a 30W higher TDP (250W) than the 3070 is (220W), depending on if you buy an OC'd card you should be in the 220-240W range with the 3070? Seems like a 650W power supply should have you adequately covered with some headroom to spare. Not sure if you are running multiple cards or other peripherals though.

At the TechPowerUp site description for the 3070, they list the Suggested PSU to be 550W which makes sense.