I rent a condo apartment for a couple of months in winter and I have never experienced a blackout either in or out of the complex. I'll try to find my bill to tell you what Electric company is there if that helps.
We live near Dominicus. The power company is CEB (which is the sister to CEPM). The B is for Bayhibe. As AnnaC says, they have a plant on the road between Bayahibe and Dominicus. It is a private company. CEPM serves Bavaro/Punta Cana.
When the main power goes off, they fire up the huge diesel generators to generate electricity.
The power goes off where we live about once every two weeks. But, within 15 minutes, usually, it is back on. Very reliable. We posted the prices a while back. There is a base rate - I don't remember exactly, maybe equal to about $8 USD, then 25 cents a kwh. Worth the cost. We have two bedrooms with a/c and living room. Run it in late afternoon and all night, rarely pay more than 4500 pesos/month.
We do not have an electric clothes dryer, if you do, it will cost a bit more.
Generators/batteries are not necessary if you have service from CEB.
Hi Muaser, electricity in Bayahibe is very reliable. As Franco says, we do have blackouts but they never last more than 15 minutes. You might not even notice. We pay the bill to our landlord and the price per kwh on the statement is around 13 dominican pesos. I don't know how it works if you have a contract in your name - I think in that case you have to pay the base price Franco was mentioning.
Anyway, no need for generators or batteries!