I think he's talking about a water-heating solar panel, 25 feet above the water supply, that doesn't currently have any water in it. He needs a pump to fill it with water, and wonders if a sump pump will do the job.
(Not necessarily just the initial fillup: One approach in areas with subfreezing temperatures is to let the panel empty at night and refill it once the sun is up and the plumbing warm, to avoid damage from freshwater ice expansion.)
I wouldn't use a sump pump. It might be able to make 25 feet. But it's optimized for throwing a lot of dirty water really fast into negligible back pressure.
I take it you have an off-grid system and a water storage tank but no pressurized water. 25 feet of lift is about 12-13 PSI. Have you considered using the sort of 12 volt diaphragm pump that provides water pressure in travel trailers?
