If you are seeking profit from mining why don't you pay for you electric bill at the start of the year all you do is pay an avg consumption rate for your area for the whole year. Then you don't pay for your additional running cost of your mining hardware. They also offer discounts if you do pay the lump sum. They offered me a 33% discount on top of it.
Likely because a lot of companies don't offer it and/or people cant afford 1 lump sum payment. Where I live, we can go on equal payments but we are responsible for whatever amount we are over. It's pretty closely watched by the hydro company as well. If you start go big in either direction, they'll change your equal payment amount.