[jasonhansel]

I'm assuming that the need to recharge all those batteries means that, when the power gets turned back on, usage spikes very rapidly, making the problem worse.

Since those batteries aren't 100% efficient, a fair amount of this power is probably being lost to the batteries themselves.

[zx76]

Absolutely. That said, the bigger effect is actually from geysers since almost every house has one whereas batteries are not as widely spread. As the power comes back on the geyser will suddenly draw substantially since the temp will have fallen during the scheduled cut.

Accordingly there have been big govt. subsidies for geyser timers to put on your DB and solar geysers to try reduce this effect. Big information campaigns about not running the geyser all the time etc.

The consequences can be substantial, the city electricity depts. have to continually deal with substations and local transformers blowing up (literally, in an explosion, I've seen the aftermath!) because of the demand surges. Some areas are exempted from the scheduled cuts in my city to preserve older infrastructure.

Additionally, insurance companies report big spikes in claims from devices being damaged due to the unstable power as it reconnects. In my house everything is behind varying levels of surge protection, and interestingly I actually have SA made surge plugs that don't pass power through for the first 5 minutes after powering back on. This way my fridge compressor won't be damaged by unstable power (e.g. sudden substantially lower voltage, or a surge) as the scheduled cut ends.

[lbotos]

I think "geysers" are a type of hot water heater, yes?

[zx76]

Yes. Most houses in SA have electrically heated water stored in a tank called a geyser. There are other options - some apartment complexes have central heat pump hot water, some houses have on demand heating via gas - but the most common is something like a 100/150/200 litre insulated steel tank in the roof that stores hot water and regulates it to 60 degrees C via thermostat.

[lgleason]

It's what us American's call a hot water tank. Basically the same thing.