I have 2 400w and our power bill didn't get any higher than it normally is..our power company here charges like 2x as much during winter, even if your usage is less...one of my friends runs twice as much electric stuff in summer and their bill is half as much in summer too...that is how we know it is all crap and they are ripping us off...our summer bill is around $200...but out winter bill with a woodstove is usually right around $400-$500....why? Since in summer we use central Air, and also 2 window units...in winter we son't use the central heat or air and yet twice as much bill somehow....
My friend in the next county over I mentioned...their bill is around $150 in the summer and around 3-400 in the winter, but they also have a woodstove, and they run AC and a huge pool pump in summer, and yet it costs less in summer...
They seem to not notice increased consumption as long as I add whatever during the winter time...I mean first I added the 1 400w, and we watched for the bill to go up, and it never did...not during summer or winter...
Then this last winter I added another 400w and we waited for the bill to go up, and again it did not...it stayed at our usual grossly inflated price...and when it went back down for summer, it went back down to what it was before the light...so eff 'em...they charge me whatever they want...so whatever.