Explained above, I WFH, single (no kids) and have an EV - but I don't use the car for commute etc so I can be choosy about when I charge the car and take advantage of the ultra cheap periods.

Fixed price advantage is you use power whenever you want. Your average unit rate is just the price on the tariff. Predictable and safe.

Agile price changes every 30 minutes, so you need to do a little planning. But if you take advantage of the cheap periods you'll generally come out on top. My average unit rate last year was like 16.5p p/kWh whereas the standard tariff was 23-24p, so some nice savings. There's also some risk involved - the price can go up to £1 p/kWh and a few days in winter in 2024 it did that for a short while (around the peak periods) so you have to take on that risk - and obviously being exposed to the world energy markets does mean you get exposure to stuff like wars impacting global markets.

I mean there's nothing stopping you from using lots of power between 4pm-7pm it's just you'll drag that average unit rate up to the point where it's probably not worth it. When I say "use lots of power" I don't mean like I sit in the dark between 4-7pm, it's just I avoid the big ticket power users like ovens, showers, cookers etc

Not GP but I assume the fixed prices have to be fairly high to account for people using lots of power during peak demand when most people use lots of power?