12/24 inverter

I have 12/24 power inverter, rated power is 600 watt peak power is 1200 watt, modified sine wave, it’s never been out of its box as I bought it about eight months ago, but I’ve since had a 1500 watt inverter fitted so I can use my microwave and now this is no use to me, I would accept £25 for it as that is less than half the price that I paid for it.