His study of sunspots and the solar magnetic cycle led to his identification of the period from 1645 to 1715 that is now known as the Maunder Minimum.

Shortly after, in 1875, he married Edith Hannah Bustin, who gave birth to six children: four sons (one of whom died in infancy) and two daughters.

After studying the work of Gustav Spörer,[2] who examined old records from the different observatories archives looking for changes of the heliographic latitude of sunspots, Maunder presented a paper on Spörer's conclusions to the Royal Astronomical Society in 1890[3] and analyzed the results to show the presence of a prolonged sunspot minimum in the 17-18th century in a paper published in 1894.

[5] In 1882 Maunder (and some other European astronomers) observed what he called an "auroral beam"; as yet unexplained, it had some similarity in appearance to either a noctilucent cloud or an upper tangent arc.

He conducted visual experiments using marked circular disks which led him to conclude, correctly, that the viewing of canals arose as an optical illusion.

In 2022 English Heritage announced that Annie and Walter Maunder would be commemorated with a blue plaque at their former home in Brockley, London, later that year.