I have to check the rest of the PC for total power draw using a Watt meter. That tells me how close I am to pushing the PSU over its rating.

I also have to look at the PSU sticker to see if it's a single or dual rail PSU. Terms here are easy to google.

https://www.techpowerup.com/gpudb/2840/geforce-gtx-1070 puts the TDP at 150W so it could be fine.