Maybe. But some electronic equipment requires a much more closely regulated DC voltage. The only way to know is to measure the "no load" voltage from the manufacturer-supplied wall wart, and compare it to the rated voltage output (which is under load). If it's sitting right at 12 VDC, it's a regulated supply, and supplying a higher voltage could cause damage.

(IMO, a decent multimeter is indispensable gear for any solar setup, for checking actual voltage, monitoring for overcharging, and confirming correct polarity.)