Yes, this is true.

However the UK has been running its power generation asset into the sand, we are increasingly reliant on things like https://ukpowerreserve.com/

So I expect that with the relentless push to smart metres (which is an optional EU directive, irony or ironies) we will see peak costs rise to battle the loss in cheap spare capacity.

That's a battery storage company? You seem to be suggesting its a bad thing??

the battery bits they have are less than 10% of their portfolio. In fact I would go so far as to say that their battery offering is mostly hot air, as they boast about its capacity in MW, not MW-hours

if you look at their asset page:

https://ukpowerreserve.com/assets/

its basically small polluting gas an diesel gennies.

Per year. And assumes electricity prices won't go up.

It took me half-an-hour to grab the CSV files from my monitoring, a write a scrap of Python to work out the difference in prices, then double-check my workings.

I'm happy with that ROI.

What would your advice be to someone with no electric car, no solar battery, no solar panels, and no subsidy available on them? Is the smart tariff still a good deal?

Depends on your usage patterns. If your job means you always get home after 7pm, or if you cook with gas, then it may still be worth it.

£60/yr would be a good saving for a supplier switch, the comparision and admin from which could easily add up an hour's work. A good ROI indeed!

What do you use for monitoring your mains supply?

The smart battery provides the monitoring. It is literally a clamp on the meter to monitor import and export, and one on the solar panel feed to measure generation. Small bit of Python to grab it ever 10 minutes.

Likely in future calculations like this will happen automatically through smart meters.