In its last year as Utah's independent electric utility, Utah Power & Light Co. made more money in 1988 than any year in its history.

UP&L, which became a division of PacifiCorp under a $2 billion merger that took effect this week, earned $2.67 a share last year, compared to $2.32 in 1987. The previous high was $2.46 a share in 1985. PacificCorp is based in Portland, Ore.Contributing to the record performance, the utility said, was higher revenues - more than $1 billion for the year - as dry weather conditions increased energy use. Other factors include an addition of 5,000 new customers, savings from an ongoing cost-cutting program, increased coal-mine productivity and improved earnings from UP&L's non-regulated subsidiary Energy National Inc.

The wholly-owned subsidiary develops, owns and operates small alternative energy power projects throughout the country. Its increased earnings contribution in 1988 was due in part to advanced revenues from a natural gas co-generation project in northern California, a spokesman said.

For the quarter ending Dec. 31, 1988, earnings were $35 million, or 58 cents a share, on operating revenues of $250.69 million. For the same period in 1987, earnings were $39.55 million, or 66 cents a share, on revenues of $242.01 million.

For the 12-month period UP&L had net income of $160.58 million on revenues of $1.03 billion, compared to profits of $144.8 million on revenues of $982.80 million.