Cable television is available to slightly more than half the households in the Washington area, and the number served by cable is increasing steadily as political and financial hurdles are cleared and more miles of wire are strung.

With 51.2 percent of households having cable access, Washington still lags far behind the nation as a whole, in which the proportion is estimated at 75 percent by the cable industry. Almost half -- 49.7 percent -- of those with access actually subscribe to cable service in this area, compared with 55.9 percent of wired homes across the country.

Not only is the Washington area behind the rest of the country, but the pattern of cable's availability here also is not what you might think. Exurban Charles County has had cable service for more than 20 years, Reston for 15, and two of Anne Arundel County's cable companies have been in business since 1971.

On the other hand, in the District of Columbia, where even the U.S. Senate has agreed, at least temporarily, to allow television coverage, would-be subscribers are still waiting for District Cablevision to begin installing cable.

To be sure, there were recent assurances that construction will begin by August and that cable will be available to 10,000 to 15,000 homes by year's end. Early construction is to focus on Ward 1 (the Adams-Morgan and Columbia Heights areas in Northwest) and Ward 8 (southeast of Anacostia).

In Montgomery County, where only 21,000 homes -- fewer than 10 percent -- have cable service, wiring has been halted. The firm that was awarded the franchise, Tribune-United Cable, may be sold to a larger company, Hauser Communication, which owns Arlington County's cable system.

Tribune-United has asked county officials for concessions in the franchise to allow it to cut the services and scope of cable television in Montgomery. County Executive Charles W. Gilchrist, who has been highly critical of the system because of a backlog in hooking up customers and a poor record of customer relations, has yet to rule on the request.

Meanwhile, county officials said last month that 9,000 new cable units for individual households had been purchased and will be used soon to hook up homes, mostly in the Montgomery Village area.

Cable service around the metropolitan area may wind up being a case of "first with the most" because money is tighter and the profits in some cases smaller.

In Montgomery County, where Tribune-United had promised to offer 32-channel service for only $1.50 a month, a former sales executive for Tribune-United said the company's difficulties arose because it was trying to offer "country club service at bargain basement prices."

In Fairfax County, where Media General's 100,000 subscribers give it the metropolitan area's largest audience, its bargain billing -- $3.07 a month for 62 channels -- is believed by some industry analysts to be partly responsible for the company's financial straits. The Fairfax franchise in April disclosed losses of $32.8 million in the past two years and said it may seek higher rates.

Despite years of wrangling and rebidding, cable service in the District remained problematic until officials arranged a $45 million construction loan from a national cable chain, the Denver-based Tele-Communications Inc.

These specialty chains are increasing in number because some diversified conglomerates such as the Chicago-based Tribune Co., which once owned the franchise in Alexandria and is disposing of the one in Montgomery, are backing out of the cable business.

In any event, the Washington area is catching up with the rest of the nation in cable service. Alexandria and Arlington are fully wired, and cable service in most other jurisdictions is expanding. Here is a rundown:In Prince George's County, planners say that as residential areas develop, cable will follow. The county, which has two franchises, is 80 percent wired. In Charles County, officials say that all densely developed areas of the county will be wired by the end of the current expansion. In Fairfax County, where four-fifths of the homes are wired, Media General estimates that 98 percent of the homes will be wired by 1989. In Loudoun County, two companies serve the eastern county and the city of Leesburg, and officials are seeking a franchise to operate in the western part of the county around the towns of Round Hill and Purcellville. In Prince William County, four cable systems currently operate, and a county officials said the free market system "works beautifully . . . and we're getting wired faster." In Anne Arundel County, which also awards only nonexclusive franchises, there are four area services and a very small private service in the community of Heritage Harbour east of Annapolis. Although officials say the entire county will eventually be wired, there is no timetable. In Howard County, cable officials say they hope to wire an additional 5,000 households this year.