Software recommendations for plotting graphs

Right then,

For the last ten days I have been monitoring our household consumption of gas and electric. I go down to the cellar usually at 8.30pm which is beer fetching time, then take a quick reading of our gas and electric meters, mostly every night. You see although I try to be green like growing veg and composting this is an area at which I am hopeless and leave lights on etc. I want to change that.

Now I don't have Excel on this PC do want a very quick idiot proof graph plot software to help me simply show consumption per night.

I did indeed Google but the programs look like way over sophisticated maths programs. I do not need that. I am no mathematician.

I need a quick simple to use Windows program which will do this job and no more.

Anyone advise me?

Thx in advance.

The Calc application in OpenOffice is Excel-like, free and is sure to do more than you will ever need (or probably understand).