Parents at Havre de Grace Elementary rejoiced in May when the county approved almost $1 million to renovate the 43-year-old school, which needs everything from new doors and windows to an updated electrical system and a modernized media center. But their joy was short-lived and has been replaced with exasperation. The school system's estimates for completion of the renovation were about half the amount that is actually needed to do the work. Richard W. Daub Jr., president of the school PTA, said he's worried that the school will not be renovated this year because the school system recently said it would cost about $2.3 million to do the work, not the $1,026,000 originally projected. Tomorrow night, the school board is expected to appoint an architect for the building who will determine what is needed to completely renovate Havre de Grace Elementary. The board will meet at Southampton Middle School in Bel Air at 7 p.m. Donald R. Morrison, the school system spokesman, said that the architect could recommend that more money be approved to do an entire renovation, do as much work as possible for the $966,000 already allocated, or do work in phases as money becomes available. Mr. Daub said he was a member of the school's educational specifications subcommittee, which met several times in August decide how best to spend the $966,000. Mr. Daub said that Joseph Licata, supervisor of construction for Harford schools, gave the committee a written list of projects and what they would cost. That list included: $265,000 for expansion of the media center; $60,000 for media center furniture and equipment; $90,000 in ceiling work and carpeting; $130,000 for windows and doors; $178,000 for rewiring work; $235,000 for an air conditioning system; and $68,000 for architect and engineering fees. Mr. Daub presented the committee's priorities to the school board at its September meeting. And he explained how difficult it was to cut about $60,000 from the original renovation price of $1,026,000 to the $966,000 available. The committee, which included parents, teachers, administrators and others, decided to trim the $60,000 by replacing only some, not all, doors and windows. But at the same meeting Mr. Licata, who was a member of the educational specifications subcommittee, dropped a bombshell on the panel. He told the board that revised figures showed that it would cost $2.3 million to renovate the school, noting that air conditioning the building alone would cost $800,000. That's the first time that parents had been told of the disparity in the numbers, Mr. Daub said. Efforts to get an explanation from Mr. Licata about the original cost estimate and the revised one were not successful. He did not return phone calls last week. Mr. Morrison, the school system spokesman, said that the figures given by Mr. Licata were only estimates and were put together hurriedly at the county's request. The school system had tentatively planned to renovate Havre de Grace Elementary in 1996. But County Executive Eileen M. Rehrmann made renovation of the school a priority in response to a vigorous lobbying campaign by parents, teachers and administrators at the school. The school's problems include an electrical system so old it can't handle air conditioners or fans without shutting down the power in the whole building. And students can't use computers on hot and humid days because the heat could damage the machines. Mrs. Rehrmann in May earmarked $966,000 to renovate the aging school, making it one of the first beneficiaries of the transfer tax on real estate sales. The transfer tax, which went into effect July 1 at the beginning of the county's 1994 fiscal year, is expected to raise about $3 million during fiscal 1994. The transfer tax money is to be split evenly between school construction and the county's farmland preservation program.