Like 24 hours on? I mean maybe a high electric bill lol. Normally during the summer my bill for electric runs about 200-250. With the light it’s been about 260-350. So there is definitely an increase in energy usage. Also, having a 600w in that little tent might be a little sketchy, but I’m sure it would be ok lol if you want a decent light for a small space the 150w sun system HPS did me pretty good! And they’re only like $50-60