which wattage light for my tent

I have a 50cm x 90cm tent and currently use a HLG 150w QB, I want to maximize the yield from this size tent since my recent harvest wasn't too great and I was thinking of getting a 480W meijiu QB.

Do you think this light will be overkill for this size grow tent or should I get the 240W meijiu?

Regardless if it's too powerful now you may want to upgrade to a larger space in the future and you'll already have the light for it if you opt for the more powerful light option.

Sounds light you already have more than enough light. 50cm x 90cm is a tiny space and won't require much light. You're talking about less than 5 sqft of grow space. The general rule is 35 to 50 watts of light per square foot, which if rounded up would be 175w of quality lighting. So if you can afford the larger light, if it fits, and you can dim it then I'd get the 480w and run it at 50% or so. Good luck.

32 watts minimum per square foot is the rule of thumb. Most advanced LED growers aim for around 50 watts per square foot but as long as you hit that 32 watt mark you should be a happy grower