Lack of access to mod­ern forms of ener­gy ham­pers efforts to reduce pover­ty. The pro­vi­sion of elec­tric­i­ty to off-grid com­mu­ni­ties is there­fore a long-stand­ing devel­op­men­tal goal. Yet, many off-grid elec­tri­fi­ca­tion projects neglect mid- and long-term oper­a­tion and main­te­nance costs. When this is the case, elec­tric­i­ty ser­vices are unlike­ly to be afford­able to the com­mu­ni­ties that are the project’s pri­ma­ry tar­get. Here we show that, com­pared with diesel-pow­ered elec­tric­i­ty gen­er­a­tion sys­tems, solar pho­to­volta­ic sys­tems are more afford­able to no less than 36% of the unelec­tri­fied pop­u­la­tions in East Asia, South Asia, and sub-Saha­ran Africa. We do so by devel­op­ing geo-ref­er­enced esti­mates of afford­abil­i­ty at a high lev­el of res­o­lu­tion (1 km²). The analy­sis illus­trates the dif­fer­ences in afford­abil­i­ty that may be found at the sub­na­tion­al lev­el, which under­scores that elec­tri­fi­ca­tion invest­ments should be informed by sub­na­tion­al data.