Prototype solar cells are usually tested indoors and left unconnected when measurements are not being performed. While the approach being simple it does not reflect the real-life operating condition of the cells. A more realistic approach is of course to continuously operate the cells outdoors at their maximum power point for a longer period of time. An outdoor monitoring system suitable for small prototype solar cells is presented. The cells under test are protected by an enclosure with a transparent lid. An in-house developed multi-channel micro maximum power point tracker (uMPPT) provides electrical loading to the cells. Besides MPP, open-circuit, short-circuit and constant voltage modes are also possible to be set per each channel of the uMPPT, giving us a wide range of different aging tests. Temperature of the cells is measured with digital sensors, which interface directly with the uMPPT. Occasionally, an I–V scan of each cell is also measured. The scans are performed in situ without taking the cells from the rooftop to a laboratory. A control computer records measured values of voltages, currents, temperatures and weather to a database at regular intervals.