Plantas are not plants
Power service in the DR is provided by two private companies, Distribuidora del Este (AES), responsible for the east side of Santo Domingo and eastern provinces, and Distribuidora del Sur and Distribuidora del Norte (Union Fenosa), responsible for the south and southwestern part of the city and northern and central provinces.

While privatization has already occurred, reliable power supply has not yet been achieved and homes and companies still need to be able to rely on their own alternate sources.

Where to start? Do your own research on the kind of power plant you need, given the available space and capacity required. Keep in mind that many Dominicans have become experts on alternative power supplies and can be helpful in suggesting brands that work well on this island. 

Note you will need to budget for (1) the power plant (2) the installation, including cost of transportion to your premises, and (3) the small house where the plant will be installed.

Other major considerations are whether you want it to start up automatically (when the power shuts off) or manually (when someone turns it on).

If you need to install your own power plant, consider moving into an apartment complex or neighborhood where this is already resolved. 

If you decide to go ahead and buy your power plant, consult the Yellow Pages (Plantas) for different suppliers. Call up requesting quotes. Ask if they provide financing and installation services. If not, they probably can refer you to an experienced person who can install your plant. Some companies may even provide assistance in designing the “caseta” or small house where you will put the generator, in order not to disturb the neighbors with exhaust gases or excessive noise. 

Keep in mind when choosing your seller that you will need regular maintenance services for changing the oil and filters and reliable repair services for when the generator fails. The service reputation of the seller is a major consideration when making the investment. 

If you live in an apartment, an invertor is a better choice. It is fuel free, with the exception of water for the batteries, and does not require an investment in a caseta. It also has the advantage that it is noiseless and emanates no fumes. 
Places that sell inverters (inversores) can be found by looking up Plantas or Baterías in the telephone book. Usually those stocking foreign brands will sell inverters. Also look for shops selling computer accessories, such as “uninterrupted power supplies” (UPS), listed under Computadoras. Computer shops may also give you a reference. Also check major hardware, electronic or electric appliances shops.

Most Dominicans buy their plants locally to get the service and installation services provided by the dealer.