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Comment by derkoe | Hacker News Reader

Most heat pumps fall back to electric heating when it's too cold. So, on these few days you will need the same amount of electricity a typical electric heating will need.

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This is untrue. Mitsubishi hyper heat units do not have this feature, and they’re the gold standard. I wish they did, though

Hyper Heat is a tech that is on multiple different models of Mitsubishi. All of the SVZ (ducted air handlers attachable to Hyper Heat or H2i mini-splits) do support (optional) electric resistance heater kits.

That’s correct, air handlers for ducted systems can absolutely have heat strips. That’s actually pretty standard. I have never seen one for a mini split though — can you share a link?

https://ces.mitsubishielectric.com/wp-content/themes/melco/a... documents the SVZ indoor unit's ability to have electric resistance heat and be connected to Hyper Heat SUZ outdoor units.

Whether you call that mini-split or not is up to you, but it's definitely a heat pump system that is Hyper Heat and supplemental electric heat capable, and getting down to one-ton units seems "mini" to me.

Mini-split means "smaller than conventional system ["mini"], condensor and evaporator are connected by long refrigerant lines ["split"]". It doesn't necessarily mean "wall/floor/ceiling indoor unit that has no ducts", though a "ductless mini-split" is the most common configuration of mini-split (because of the cheapness and ease of installation). https://zeroenergyproject.com/2022/03/09/what-is-a-mini-spli...

which spikes the electricity demand from the grid and puts it under the most strain when its most critical for the grid to stay up, which means the grid has to be overdesigned, which means that the air based heat pumps are a poor choice for a reliable grid.

It depends on where you are. In many places worldwide, extreme cold is also generally quite clear from clouds unless you're literally in a storm, in which case, the high winds are just as likely to cause problems. Rooftop solar should be more than enough to offset your own usage.

In nearly all places extreme code means dark! Sure there are less clouds, but the latitude is high and so there are not only few hours of daylight, the earth's angle is also working against solar.

The demand comes at the coldest part of the day, which is typically overnight, which is far off peek demand times.

I don't think this conclusion follows. It is true that variability is a challenge for grids, but it is not clear that it is better to trade more total energy usage (per useful unit of work) for less variability. Variability is certainly a challenge, but not an insurmountable one, and also one that must be faced regardless nearly everywhere, as solar power has become too cost-effective to be ignored.

Isn’t electricity demand always going to be highest on the coldest days?

The UK is rolling out smart meters to every property. In the past 2 winters (following on the Russian gas crisis), they have run programs that pay £3 per kWh reduced demand. This is a nice way to balance the grid during extreme demand.

> programs that pay £3 per kWh reduced demand.

That much? How do I get in on that?

My energy supplier's demand reduction scheme only pays £10/month total.

octopus energy seems to be the best for energy i have seen so far in the uk alongside their smart tariffs https://share.octopus.energy/umber-squid-619

It's called the National Grid ESO scheme and you sign up through your supplier when it's open. However, some suppliers take a cut of the ESO payment. Alternatively, you can sign up to Uswitch Utrack (https://www.uswitch.com/mobile-app/), which passes 100% onto the customer. (Disclaimer: I used to work at Uswitch.)

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