Don't know if the OP was from the UK, but UK night rates are of the
order of half the day rate (though you have to pay a higher day rate to
qualify!), but only for 7 hours. I do wonder if it would be possible
now to set up a battery/inverter/load sharing system sufficiently
cheaply to lower the cost of daytime use significantly. Probably
illegal though.
================================
Why would it be illegal storing energy ? I can't imagine that it is
illegal charging the batteries of a Golf buggy , at night tariff.
I am sure any golf club would do that to reduce their electricity bill.

BTW ,living in the UK myself ,night tariff indeed normally starts at
about 2300 hrs and finishes at 0600 hrs the following morning .
At our place switching happens with an electro-mechanical timer with a
spring mechanism such that following an outage the timer keeps running.
Eventually that spring has to be re-wound by the electricity supplier
,but that hasn't happened the past 15 years........so the timer at our
place now comes into operation around 2320 hrs ,but then of course also
day tariff starts about half an hour later at 0620 the following morning.

Frank GM0CSZ / KN6WH