June 14 (Reuters) - New Zealand shares rose on Monday as heavyweight electricity companies clocked strong gains, with investors awaiting the Federal Reserve meeting due later in the week for clues on U.S. monetary policy.

The NZX 50 index rose 0.2% to 12,573.4 points in thin trade, with about 1 million shares changing hands compared with the 30-day average of 32 million, as Australian markets were closed for the Queen's Birthday holiday.

Energy retailer Mercury NZ Ltd led gains on the , up 1.7% to eye its biggest one-day jump in nearly two weeks, while peer Meridian Energy Ltd climbed 0.8% after posting a 23.4% rise in its May New Zealand retail sales volumes. (Reporting by Yamini C S in Bengaluru; Editing by Peter Cooney)