There is no standard governing what a contractor may charge a customer for an after-hours call. No code sets it, no regulation fixes it, no consensus standard defines it. A trip charge and an evening or weekend multiplier are commercial terms between you and your customer, set by your own price book and whatever service agreement you have in place. That is worth saying plainly, because a lot of template copy implies otherwise, and a contractor who believes 1.5x is a rule is in a weak position the moment a customer asks where the rule comes from.
What is regulated is what you PAY. The Fair Labor Standards Act requires not less than one and one-half times the regular rate for hours worked over forty in a workweek. California adds daily overtime after eight hours and double time after twelve. Neither has anything to do with your invoice, and neither creates a night or weekend premium as such: federally, a technician working 6pm to 10pm on a Tuesday who has worked twenty hours that week is owed straight time. The two ideas happen to share the number 1.5, which is exactly what makes them so easy to conflate. This builder keeps them apart — billing multipliers are editable defaults labelled as convention, and the pay figures are carried separately with their citations so you can see what a 10pm callout actually costs you.
The other number worth being careful about is the estimate of missed revenue. A missed call is not a lost job — some callers try again, some were price-shopping, some had a problem that resolved itself. So the figure here is your own average ticket multiplied by the number of calls nobody reached, and it is labelled an estimate everywhere it appears, on the page and on all three exports. It is built from your data rather than from an industry benchmark, which makes it defensible as what it is: a projection worth acting on, not a receipt for work you lost.