Thermochemical　heat　storage　materials　offer　high-energy　storage　densities　and　clean　means　of　long-term　solar　energy　storage.　The　aim　of　the　study　is　to　assess　the　potential　heat　storage　efficiency　of　salt　hydrates,　based　on　sufficient　hydration/dehydration　performance,　water　sorption　and　cyclicability.　MgSO4　7H2O,　ZnSO4　7H2O　and　FeSO4　7H2O　were　evaluated　based　on　preselected　criteria.　The　main　highlights　of　the　dehydration　result　show　that　higher　enthalpy　was　obtained　for　MgSO4　and　ZnSO4,　shows　2256　and　1731　J　g−1　enthalpy,　respectively.　During　hydration　process,　six　water　molecules　were　absorb　by　MgSO4　and　ZnSO4　after　pre-dehydrated　temperature　150°C　and　120°C,　respectively.　The　cycle　stability　of　MgSO4　and　ZnSO4　showed　better　performance　which　give　rise　1210　g−1　and　1155　J　g−1　enthalpy,　respectively.　It　was　expected　that　FeSO4　would　show　higher　cyclicability　due　to　their　higher　enthalpy　(1400　J　g−1)　in　the　first　round;　however,　overhydration　does　not　permit　it　to　released　larger　energy.　The　impact　of　relative　humidity　on　water　sorption　performance　and　rate　of　hydration　were　reported　which　showed　that　MgSO4　and　ZnSO4　can　uptake　maximum　water　under　85%　and　75%　relative　humidity.　Ongoing　studies　and　the　booming　progress　of　ZnSO4　7H2O　illustrate　that　likewise　MgSO4　7H2O,　it　is　also　the　potential　candidate　and　can　be　use　in　thermochemical　heat　storage　devices.　To　bring　zinc　sulfate　heptahydrate　into　market,　more　detail　studies　in　fields　of　evaluation　of　advanced　materials　and　development　of　efficient　and　compact　prototypes　are　still　required.　©　2020　John　Wiley　&　Sons　Ltd