Yes, exactly. Watt's law is volts * amps = watts. (600 x 12 = 7200 watts just as 300 x 24 = 7200 watts)
Many of the items on my coach 24VDC (water pump, lights, inverter, etc..). However; some are simply available only in 12VDC (hose reels, ceiling fan, dump valve, some lights, etc.) so a...