HOUSTON, Jan. 15 — Electric utility Florida Power & Light Co. proposed building 1,900 Mw of combined cycle gas-fired capacity by 2005 to serve an additional 40,000 consumers and maintain a 20% reserve margin.

The two projects would increase the Juno Beach company’s capacity 10%. FPL, a unit of FPL Group. Inc., said the decision to build the units itself was the result of the utility’s “comprehensive evaluation of power purchase proposals from other companies and FPL-formulated alternatives.”

FPL didn’t say when it expected to begin construction or estimate the cost of the proposed plants.

The evaluation showed expansion at existing FPL sites was the most cost-effective option and represented the best balance of economic and environmental considerations, the company said. FPL’s expansion proposal calls for adding 1,100 Mw of natural gas-fired combined cycle generation at its 9,500-acre Manatee plant near Bradenton on Florida’s west coast.

Conversion of two existing gas combustion turbines into combined-cycle gas generation, along with two new turbines, would add an additional 800 Mw at the 11,300-acre Martin site near Indiantown, Fla. The Martin site gas peaking units planned for conversion are turbines currently used for short periods of time to meet high customer use in the summer or winter.

Thanks to a new gas pipeline serving the state, Pres. Paul Evanson said FPL is planning to use gas in combination with oil at the existing Manatee generating units. He said adding natural gas at FPL’s last remaining oil-fired generating units will improve their environmental performance. The plant was the subject of a long-running controversy over a proposal to import heavy oil from Venezuela to burn in the plants.

The plant expansions are subject to various regulatory approvals.