That is a nice question, and science is presently grappling with that question. Perhaps the expansion of space creates energy. Positive energy along with negative energy. The four fundamental forces and gravity, matter and anti-matter. The answer will only be available in future. People can certainly abort that search with "Goddidit", as they have been doing all along. Zero-energy universe - Wikipedia
First of all, Wickipedia is Not a Bible book.
I can agree that there are answers that will only be available in future time -> Jesus' Millennial time of governing over Earth.
New scrolls (new books) will then be opened, so answers will then be available according to Revelation 20:12.
In the Bible, expansion of space is caused by God according to Psalms 33:6; Hebrews 11:3; Isaiah 40:22; Jeremiah 10:12; Jeremiah 32:17; Jeremiah 51:15 B.
So, Creator God, His 'power and strength' (great energy) causes the expansion of space - Isaiah 40:26 B.