100 watts to 150 watts is not going to be a noticeable gain in your electric bill.
If it costs you $.10 per kilowatt hour, and you had the lights on 18 hours a day for 31 days (longest month). Your average electric bill would be:
100 watts = about $5.58 per month
150 watts = about $8.37 per month
P.S. - Hopefully you aren't talking about incandescent equivalent wattages.