20% efficiency in terms of light -> electricity. A 50% laser efficiency (electricity -> light) is really good, possible for some diode lasers, if you pump a fiber laser with diodes to get a high quality beam for cutting materials or weapons purposes maybe you get 25%.

That demo would require about 45 kW of laser power with good beam quality which would be totally possible with a fiber laser

https://www.rp-photonics.com/wall_plug_efficiency.html

Wow that's a long way from the proposals for sending GW of microwave power from satellites.