Selectively-absorbing nanofluids were synthesized and evaluated for spectrum splitting PV/T collector applications. Core-shell silver-silica (Ag-SiO2) nanodiscs and multi-walled carbon nanotubes (MWCNTs) were suspended in water at varying dilutions and then tested as an optical filter placed between a light source and silicon solar cell. A concentrated Ag-SiO2 solution diluted with an aqueous MWCNT solution yielded higher thermal efficiencies than when diluted by the same volume of water. However, AgSiO2-MWCNT mixtures yielded a lower electrical output than aqueous AgSiO2 dilutions due to the non-selective absorption of MWCNTs. The most concentrated Ag-SiO2 nanofluid (0.026wt%) yielded a peak thermal efilciency of 65%, to deliver the greatest combined efficiency of ∼72%.