Bests & Worsts Reviews from Amazon

Note: there are many models of BESTEK 12 VDC to 110 VAC inverters. This review covers only the BESTEK “300W Sine Power Inverter”, model MRZ3011HU-US. Distortion: This inverter is advertised as “pure sine wave inverter”BESTEK 300W Power Inverter DC 12V to AC 110V Pure Sine Wave Inverter with 4.2A Dual Smart USB Ports Car Adapter. Considering the price I did not expect the AC output to be very “pure” but hoped it would at least be better than the “modified sine wave” from most inexpensive inverters. I was quite surprised to see that the output is a very clean sine wave (see photo) with total harmonic distortion plus noise measuring less than 3.5% at 100 W output. The actual distortion may be considerably better than 3.5% as the measurement was the limited by the noise of the test equipment used. Distortion was only measured at 100 W output but the shape of the sine wave did not appear to change from no load up to 280 Watts Start-up: The AC output is very well behaved on start up when the inverter is powered on (see photo). There are no large transients and the AC output voltage ramps up smoothly over a period of approximately 400 ms. The start-up waveform is the same regardless of the load on the inverter. Regulation: The output voltage of the inverter was very well regulated. With 14 VDC input, the output voltage varied from 109.9 VRMS at no load to 108.9 VRMS with a load of 285 Watts. With a 100 Watt load the output voltage varied from 109 VRMS with 12 VDC input to 109.4 VRMS with 14.5 VDC input (see plots). Efficiency: With 14 VDC input and a 100 Watt load the efficiency of the inverter measured 88.4%. That is very good for an inverter with true sine wave output. Efficiency at full load drops slightly and measured 86.4% with a 285 Watt load and 13.1 VDC input. AC ground: The inverter AC output floats relative to the DC input. Neither the neutral or the ground of the AC outlet connects to the negative lead of the DC input. The ground pins of the two AC outlets are not connected to chassis ground or to each other. Sound level: The inverter has a fan that runs continuously when the inverter is on. I did not find the sound level objectionable when the inverter was on the floor of the vehicle and fan was facing away. For comparison, the fan in the inverter was approximately the same sound level as the vehicle heater/AC fan when it is set on “medium” speed. Other features: The inverter has a “NO/OFF” switch (see photo). It appears to function the same as an “ON/OFF” switch. Summary: the performance of the inverter is very good and it's a great value for the price ($32.99).