Fast delivery and shipping. It appears to be a very modified sine wave as there is no electromagnetic noise or radio interference in motors like fans. The output voltage is well controlled at any load up to the rated maximum. At 1200W an alarm will sound and the output will shut off immediately, which is great for the longevity of the inverter, but don't expect to get the advertised peak power (2400W for the 1200W model) for even a split second to be able to use. per second and even more for the 20 seconds they advertise. It is also very efficient compared to other non-mainstream brands and generates very little heat, <10% load power. By far the best value for money.