It really depends where you are - if you are in a rural area with above
ground lines and lots of ice storms, hurricanes, etc. then not too good. In
an urban area with buried lines, power may go uninterrupted for years at a
time.

If it's critical that the clock not stop you can put it on a UPS battery
backup.



"Mike Berger" wrote in message
...
In the U.S. the power grid is very accurate over long periods of
time. But what are the odds of running six months without a single
power interruption?

Christopher Tidy wrote:
Hi all,

I'm thinking of building an electronic clock control circuit which uses
the 50 Hz mains frequency for time keeping. The reason for this is that
the clock dial is rather large, so probably wouldn't run for long on
battery power, and I don't fancy spending £40 buying a programmable
quartz oscillator chip.
...

From my point of view I'd regard an acceptable error as 5 minutes every
6 months. Does anyone know the typical time error seen on the UK grid, or
where I might find this information? Any suggestions would be much
appreciated.