Charles Spurgeon Commentary 1 Chronicles 28:15

"by weight also for the candlesticks of gold, and for the lamps thereof, of gold, by weight for every candlestick and for the lamps thereof; and for the candlesticks of silver, [silver] by weight for [every] candlestick and for the lamps thereof, according to the use of every candlestick;" — 1 Chronicles 28:15 (ASV)

They were not for the burning of candles, but for oil lamps.

There was a lampstand, with seven lamps on it; and there were ten of these in the temple. There was only one in the tabernacle; but there were ten in the temple. David arranged everything.

Those seven-branched golden candlesticks stood like pastors of the church; and the little silver candlesticks were carried about like evangelists, who go from place to place so that the whole house of God may be served with light. Everything was by weight. God knows what he would have in his house, and he measures out to each one according to his need.