According to the Bureau of Labor Statistics, in 2012 there were 124.4 million total households in the U.S. --- and 27.6 million of those (22.1%) had no "earners" at all.
An "earner" as defined by the BLS: "A consumer unit member, 14 years of age or older, who reported having worked at least 1 week during the 12 months prior to the interview date."
A "household" could be anything from a beach-front mansion to a weekly motel room or a mobile trailer.
The Bureau of Labor Statistics reported there were a total of 156.1 million "earners", but the Social Security Administration reported 153.6 million "wage earners", which are those who pay FICA taxes and might not include those whose only income is derived from unemployment benefits, Social Security retirement or disability benefits, a pension plan, capital gains from investments, stock-option grants, a trust fund, an inheritance, an insurance or civil settlement, or an annuity (or any income by illicit means).
Here's the breakdown from the BLS report:
There were 75.6 million households with 2 or more people:
11.7 million of those households had no earners at all
26.0 million of those households had only one earner
39.7 million of those households had two earners
9.9 million of those households had three or more earners
- There were 49.6 million households with 2 or more people that had multiple earners.
- There were a total of 135.1 million earners in households with 2 or more people.
There were 35.9 million single households:
15.9 million of those single households had no earner at all (average age was 67.6 years old) and 37% were men, while 63% were women.
21.0 million of those single households had only one earner (average age was 44.1 years old) and 54% were men, while 46% women.
...Sub-total: 135.1 million earners in households with 2 or more people
+ Sub-total: 21.0 million earners in single households
= TOTAL: 156.1 million earners in 124.4 million U.S. households*
*As was previously noted: The Social Security Administration reported that the U.S. had 153.6 million "wage earners" --- for a difference of 2.5 million "earners" the BLS reports (who may have other means of income) --- but 50% of all U.S. "wage earners" took home $27,519 a year or LESS.