In some cases it is because the consumer has opted for variable rates, essentially making a bet that net-net, variable rates will be less expensive than the fixed rates. Or that they would be able to shift usage to reduce usage during spikes. See: https://www.texastribune.org/2021/02/22/texas-pauses-electri...

Also see: https://www.ft.com/content/0e746280-e72c-4087-9c0d-df2a7af82...

Feb 2021 FT: "Bills mount in Texas power market after freeze sends prices soaring: Financial casualties emerge as grid operator Ercot requires billions in payments "

In Alberta, the electricity system has been deregulated so you can buy from numerous providers. The Utilities Consumer Advocate shows 187[0] different electricity plans available in my city. My currently plan and provider changes rates monthly, but some providers allow you to sign up for 3-year or 5-year fixed-rate plans.

Thanks to deregulation, the electricity rate isn't the only thing you pay for though. There is also a Transmission Charge, Distribution Charge, and Local Access Fee. These are all per-kWh charges and change very rarely.

In October, my electricity rate is $0.10730/kWh, but my total cost is actually $0.16346/kWh plus the per-day charge ($0.202/day). Tomorrow the November rate will be published.

[0] https://ucahelps.alberta.ca/cost-comparison-tool-result.aspx...

This also depends on the country. Where I live (Europe) the rate now changes by the minute, or thereabouts. That was made possible after everybody had to change to wireless meters. Sometimes you'll get a warning in advance - a newspaper may write "If you live here or here, don't do your cooking at this particular hour". Some providers still have fixed rate options, some apparently don't. What I dislike the most is that they're trying to force us to run our washing during the night, something the insurance company and the fire department warn intensely against. And I don't want to be at sleep if a fire starts (which happens here and there, through the year). But that's what the pricing scheme tries to enforce.

Octopus Energy in the UK has a tariff that charges half-hourly rates. They also offer an API to interrogate current pricing and usage and encourage their customers - including domestic users - to take advantage of it: https://developer.octopus.energy/docs/api/

Here are providers that offer spot pricing to consumers:

https://www.flickelectric.co.nz/pricing-and-plans

https://www.pauatothepeople.co.nz/cheap-as.html

Aside from this, peak / off-peak pricing is not unusual.

I’ve never seen such a thing. Every locale here has a meter and you are charged monthly for exactly how much you use. Just like water.

TVA in the United States has a variable rate per month due to fuel surcharges.