I am at the point to calculate the Annualized cost.  Annualized Replacement and Capital cost have been calculated accordingly.  But I got poblems by calculating the Annual O&M and Annual Fuel Costs.  Project lifetime 20 and every year different values due to the increasing load I used in my Spreadsheet. Can I use average values?

The best thing would be to calculate the net present value of all the yearly costs.  In other words, discount them all to the present and sum them up to find the total net present cost.  Then you can annualize that net present cost by multiplying by the capital recovery factor.

To discount a cost in year N back to year zero, divide it by (1+i)^N where i is the discount rate.