import re
text="Energy (kWh/m²)"
print(re.sub(r'([²³¹⁰ⁱ⁴⁵⁶⁷⁸⁹⁺⁻⁼⁽⁾ⁿ])|\W', lambda x: '' if x.group(1) else '_', text))
print(re.sub(r'[\W²³¹⁰ⁱ⁴⁵⁶⁷⁸⁹⁺⁻⁼⁽⁾ⁿ]', '_', text))
aW1wb3J0IHJlCnRleHQ9IkVuZXJneSAoa1doL23CsikiCnByaW50KHJlLnN1YihyJyhbwrLCs8K54oGw4oGx4oG04oG14oG24oG34oG44oG54oG64oG74oG84oG94oG+4oG/XSl8XFcnLCBsYW1iZGEgeDogJycgaWYgeC5ncm91cCgxKSBlbHNlICdfJywgdGV4dCkpCnByaW50KHJlLnN1YihyJ1tcV8KywrPCueKBsOKBseKBtOKBteKBtuKBt+KBuOKBueKBuuKBu+KBvOKBveKBvuKBv10nLCAnXycsIHRleHQpKQ==