Best way to drop 10volts at 0.25A with linear regulator?
you're planning to burn up 2.5 watts a TO220 part is going to need a heatsink at that power level, but you can put a resistor in series with the input and make the heat there where it's not damanging anything







simulate this circuit &ndash; Schematic created using CircuitLab

at low current the reguilator sees near full voltage, but the current is low so there's not much heat made. at 250mA R1 is dropping about 8V so the regulator is only working with 6V in and so making less that 1W of heat