  Widespread air source heat pump (ASHP) adoption faces several challenges that
on-site thermal energy storage (TES), particularly thermochemical salt hydrate
TES, can mitigate. No techno-economic analyses for salt-hydrate-based TES in
residential applications exist. We quantify the residential space heating value
of four salt hydrate TES materials - MgSO4, MgCl2, K2CO3, and SrBr2 - coupled
with ASHPs across 4,800 representative households in 12 U.S. cities by
embedding salt-hydrate-specific Ragone plots into a techno-economic model of
coupled ASHP-TES operations. In Detroit, salt hydrate TES is projected to
reduce household annual electricity costs by up to $\$$241 (8$\%$). Cost
savings from TES can differ by over an order of magnitude between households
and salt hydrates. We identify the most promising salt in this study, SrBr2,
due to its high energy density and low humidification parasitic load.
Break-even capital costs of SrBr2-based TES range from $\$$13/kWh to
$\$$17/kWh, making it the only salt hydrate studied to reach and exceed the
U.S. Department of Energy's $\$$15/kWh TES cost target. Sensitivities highlight
the importance of variable TES sizing and efficiency losses in the value of
TES.
