A professional Business plan is written on Excel lets analyse why should it be excel is there any rule which says it should be written on excel format and not other’s like word or presentation template
Lets look at it in technical ways, when you write in excel format it gives you flexibility to have numbers with formulas which will save your time in calculating if one parameter is changed. For e.g if you increase your sales from 10 per month to 20 excel automatically calculates the total revenue generated if you have given formula to multiply.
This feature is not possible in presentation templates and when you have lengthy sheets of cash flows accommodating 36 months cash flow is not possible in word.
Yes the feature of excel is well suited to help you by auto dynamically calculating cells as per the formula given by you, this helps you to check and re check with possibilities of revenue that can be earned.
Writing Executive summary , vision & mission and other descriptive can be in word format, with regard to showing projections in brief or showing product demos power point is best suited.
Yes I do know when you wrote your first Business plan in college of competition it was on power point with all the fancy fonts, display and color schemes. That was to prove point on the idea that you presented with market details, how to generate revenues, but actual financials need to fall in excel format.