In counting populations it is necessary to consider which names are variant spellings of the name, resulting from the family spelling differently, illiteracy, or mistakes by the enumerator. Minor spelling differences are clearly variants of the same name, and there are additional clues from distribution by county. There are 36 Kellsall in 1881 and 35 in 1901, and 19 Kelsal in 1881 and 18 in 1901. I consider that these are clearly variants of Kelsall along with the less common Kelsale, Kelshall and Kalsall and are in effect the same name. On the other hand the name Kessell/Kessel was concentrated in Devon and Cornwall in 1881 where there were no Kelsall, and I think this is clearly a different name. I am uncertain about Kelshaw which had a population of 260 in 1881, mostly in Lancashire and Yorkshire. The relatively low incidence in Cheshire and Staffordshire combined with a high proportion in Yorkshire leads me to think that this name has a different origin.
Variant spellings can also be examined in the UK electoral rolls from 2002 to 2014 available on FindMyPast. Looking entries (which do not equate to population since many people will appear on more than one roll), there are 4944 Kelsall, 37 Kelshall, 13 Kelsell, 11 Kellsall, 9 Kelsal, 4 Kellsal and 1 Kelsaw. These spellings are likely more official than those found in census records collected by enumerators There were 359 Kelshaw.
Data from 1881 are shown below, followed by variant counts from the England and Wales census from 1841 to 1911.