Thank you, just received back, energy price seem stable now  

Honestly, as i thinking : the energy price (before fixed) appropriate for current system price.
Now, if you want to fixed it to avoid farming day by day because of revenue from ads count time is 24h, i think something you should change to encourage new user ( nobody want to spend a lot of time to typing captcha + watch ads just to earn some cent a day):
Energy recovery speed.
Resources price.
Offline Miner price/upgrade.