Several groups promoting solar energy uses complained yesterday that candidate Jimmy Carter promised steps toward a sun-powered future that President Jimmy Carter seems to have forgotten to take.

Solar Action Inc. joined forces with representatives of various consumer and environmental pressure groups at a press conference to point out that the proposed 1979 budget allocates $400.5 million for solar applications while the 1978 budget was $410.7 million.

Instead of a moral equivalent of war on energy waste, said Solar Action director Denis Hayes, referring to Carter's key demand, "this is not even the financial equivalent of one small weapons system."

John Abbott of the Public Interest Research Group, a Ralph Nader organization, made public a memo from the old Energy Research and Development administration, now part of the Department of Energy, to Carter's preinauguration transition team. The memo was obtained under a Freedom Of Information Act request, Abbott said, and included the observation that the public "would very likely be strongly opposed to a minimum solar r&d (research and development) program."

It added that "a sound rationale . . . cannot be constructed at this time" for a minimum program. Yet the minimum total the memo rejected was $440 million, 30 million more than has actually been proposed. "I'd like to know whether ther's a new rationale and what it is," Abbott said.

The White House press office acknowledged the reduction, noting that the bulk of it was in solar heating and cooling demonstration projectds. Enough of that program has been completed as planned to justify the reduction, especially since increases in other areas total $18 million, a spokeswoman said.

"The question is whether there have been increases in useful kinds of places, and we think there have," the White House office said.

The group of solar energy advocated complained that what solar funding there is tends to be reptitive unimaginative and focused on residential and commercial applications rather than on agriculture, industry or transport, which together make up two-thirds of the nation's energy use.

President Carter, said Herb Epstein of Environmental Action, has done none of the symbolic ribbon-cutting or tours of solar facilities that he has performed for the benefit of nuclear energy projects. There are fewer small-scale demonstration projects that could familiarize people with solar applications and more of the centralized big-technology operations that most solar advocates seek to avoid, Hayes said.