Albert Barnes Commentary 1 Kings 5:11

"And Solomon gave Hiram twenty thousand measures of wheat for food to his household, and twenty measures of pure oil: thus gave Solomon to Hiram year by year." — 1 Kings 5:11 (ASV)

The amount of wheat was considerably less than Solomon’s own annual consumption, which exceeded 32,000 cors (1 Kings 4:22). However, the small amount of twenty cors of oil, which at first sight seems to hardly match the 20,000 cors of wheat, is not improbable if we consider that the oil was to be “pure”—literally “beaten,” that is, oil extracted from the olives by pounding and not by using a press.

Year by year—This refers to all the years that Solomon was engaged in building and was helped by Hiram.