How do I actually calculate the right generator size for my site?

List every piece of equipment expected to run, note its power draw, apply a diversity factor for realistic overlap rather than assuming everything runs simultaneously, then check the largest motor's starting surge against the resulting figure, and finally add a 15 to 25 percent safety margin. This sequence, done properly, gives a far more accurate kVA figure than simply summing nameplate values. Skipping the diversity factor step typically leads to an oversized and inefficient generator. Sparkline Group's technical team performs exactly this calculation with site engineers before recommending equipment. It is worth having this reviewed rather than relying on a rough personal estimate for anything beyond a very small site.