400w is not going to cause a major change in your electricity bill.

I could be wrong but i think a average computer left on 24/7 uses approx 200-300 watts.
Large flatscreen LCD/Plasma TV's use a lot more.

If you pay your bill on time, having a high bill is not really an issue.
CashandPrizes Reviewed by CashandPrizes on . Electricity spikes I am about to begin a grow, I am planning on using a 400 watt HPS with MH conversion bulb for vegetation. would using this light cause a noticeable spike in my electricity usage in which authorities would come to see me? Thanks for the advice. Rating: 5