NASHUA — City residents can expect to see about a $130 increase in their property taxes once the new tax rate is set this fall, according to preliminary estimates released this week. (More Nashua news, Page B2.)

“This is an educated estimate,” Mayor Donnalee Lozeau told the aldermanic Budget Review Committee Tuesday.

City officials are anticipating that the increase in the tax rate should not be higher than 2.5 percent, which would change the tax rate from $20.97 per $1,000 of assessed valuation to about $21.54.

The average homeowner with a house assessed at $250,000 in Nashua is currently paying about $5,242.50 in property taxes; that would increase to about $5,373.50 under the preliminary figures.

According to Lozeau, this would represent about an $11 increase a month for the average homeowner. However, the final tax rate will not be official until it is set by the New Hampshire Department of Revenue Administration, likely at the beginning of November.

John Griffin, chief financial officer, said there is a total surplus of about $4.7 million from the city’s 2012 budget, which includes about $2.5 million in unspent appropriations.

“That is a lot of money,” Alderman-at-Large David Deane said of the surplus.

Lozeau has filed proposed legislation that would apply $4.3 million of the unassigned general fund balance, or surplus, to offset the tax rate. The remaining $400,000, she said, will be used to increase the undesignated fund balance.

Her proposed resolution was supported by the budget review committee on Tuesday, and will go before the full Board of Aldermen for a vote on Sept. 25.

If approved, the city’s undesignated fund balance will be about 11.9 percent, with a current overlay of about $1.8 million, said Lozeau. Last year’s overlay was around $1.5 million, she added.

Alderman-at-Large James Donchess said the city should not typically go above 10 percent for its undesignated fund balance, but said he is supporting the nearly 12 percent this year, in part because the state adequacy grant formula for school districts could be adjusted, cutting city revenue by $5 million.

Last month, the Board of Aldermen approved nearly $2.4 million in escrow requests from the mayor, which were a result of unexpended appropriations from last year. The money is now being used for various projects and capital improvements throughout the city.

Earlier this summer, the board finalized the fiscal year 2013 budget of $230 million.

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Kimberly Houghton may be reached at khoughton@newstote.com.