Dear respected,
Good day! Welcome to Microsoft Community.
We went through your post carefully and do understand your demand to show results automatically based on the drop down field selection. If my understanding is correct, we would like to convey that this can be done by Nested IF formulas.
I deployed the tests with a Choice field similar to your drop-down field, you can simply edit the field name in the below formula and add the following conditions like 3PH63A......
=IF([condition drop down]="1Ph 63A",1000)+IF([condition drop down]="2Ph 63A",1200)
Here you can have the video to better understand: How To Use IF Statements In A SharePoint List Calculated Column - Microsoft Community Hub Meanwhile, notice that there is a limit in SharePoint on the nested IF statements you can embed within the formula this is currently set at 19. If you need more than 19 conditions, the workaround can be referenced from here: Nested If in SharePoint List - Microsoft Community
Appreciate your understanding that sometimes the initial reply may not resolve the situation very soon. However, we can work together to narrow down and resolve the situation. Please kindly post back and provide the more information, then we can focus on your specific scenario and provide specific suggestions.
We'll be here for you to wait for your updates. I appreciate your time and effort on checking these above and thank you for your patience and cooperation. I hope that you are keeping safe and well!
Sincerely,
Mia | Microsoft Community Moderator