What Kw size generator to purchase? 3k sf home w/ 3 heat pumps for heat & A/C. Elec oven and water heater.?

I am renovating a 3000 sf home and want to add a whole house, automatic generator. The generator will use LP fuel and have an automatic transfer switch. The home will have 3 heat pumps for both heat & A/C (3-ton, 2-ton, and 1-ton). Additionally, it will have two electric ovens and electric water heater. What size generator should I be shopping for? Thank you.