Economic value of labour

Hi guys!

I have a simple question:

A worker gets paid $x per hour.

Some event (maybe a power failure in his office) stops
him from doing the work for 1 hour.  He still gets paid.

What is the average total economic welfare cost of this event as
a result of the worker being unable to work?

What is the correct way to handle this question?

I assume that to the employer, the work is worth $y (greater
than $x), so the worker loses $y.  If the worker is indifferent
to doing the work, this is not a factor.  But the purchaser
of the employer's product may lose out more than the selling price
if the product is unavailable.

Does the total cost depend on income tax or VAT/GST rates,
or Cor****ation Tax?

I would like to be able to work out the typical total cost of
a delay on the metro, a power failure, or being stopped by the
police for questioning.

This calculation must be routine in economic analyses - but
I'm not sure what to Google(tm) for - I'm not an economist.

Thanks in advance for any advice or pointers!
--
Anon