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Energy-harvesting systems provide power autonomy to individual wireless sensor nodes, allowing simpler deployment, as compared with wired nodes and longer lifetimes than battery-powered ones. Indoor light energy is an abundant source in many applications where solar cells are used to convert the radiant energy to electricity. To allow the greatest functionality in nodes powered by light energy-harvesting systems, the highest power output indoor photovoltaic (PV) devices are required. Amorphous-silicon and dye-sensitized solar cells have been tested extensively as indoor light harvesters due to their wide bandgaps that are optimum for absorption of the spectra from compact fluorescent lamp (CFL) and light-emitting diode (LED) bulbs. III–V solar cells are the highest performing PV devices under 1-sun conditions but have not been thoroughly investigated under indoor illumination conditions. Here, we show experimentally that III–V single-junction solar cells made from GaAs and GaInP significantly outperform amorphous-silicon and dye-sensitized solar cells at low illumination intensities with 2× greater measured power densities. Our measured data show that credit-card-sized GaAs and GaInP solar cells will provide ∼ 4 mW of power under 1000 lx (i.e., in a bright office space). This is the first thorough presentation of GaInP and GaAs solar cells under CFL and LED illumination and provides a key insight for indoor PV as we move toward wider deployment of these energy efficient bulbs.