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Comment by dahfizz | Hacker News Reader

In ideal conditions. Even good heat pumps with COP >=4 will drop below 2 when it's cold out

If it's very cold, yes. But the average should still be well above 3:

> Similarly, in Finland, tests of air-to-air heat pump systems from various manufacturers resulted in COPs of 3 at -10C and 2 at -20C.

Source: https://www.carbonbrief.org/guest-post-how-the-energy-crisis...

In the most populated regions of the UK it doesn't realistically go below -5c basically ever.

The average minimum temperature in the winter months in London is 3c above freezing.

London had a -8C night earlier this year

https://www.mylondon.news/weather/london-weather-coldest-nig...

as noted in the article - a once in 12 ish year event. So, 1/4000...

Yeah we'll be fine unless extreme weather events become more common.

But then it’s nasty blackout. Somebody still needs to design electricity grid for one of these very rare events.

Burn some fossil fuels from a "national emergency reserve". Perfect is the enemy of good.

A whole lot of other electricity demands drop massively at night, so while it needs to be planned for, the coldest nighttime period is also the time the electricity grid currently sees the lowest demand.

People are also typically asleep under a ton of duvets. It's not an issue if your home drops to say 10-15c overnight and is warmer in the day.

True. Growing up in Norway I often even preferred sleeping with my bedroom window open during winter.

I'd just whack the wood burner on. It makes sense for people to have a backup.

TBF that's not an option in London, or in apartments.

But - other comments have noted, some backup generation capability that use less green resources should be acceptable for such rare contingencies.

I live in London and used mine in the winter, gas prices were insane.

Probably a good half of our homes have fireplaces and chimneys.

It's not cost effective for everyone to have a wood burner but if only a small percentage used them on the cold days we'd be fine.

People obsess a bit about pollution, as a response to rare events it's fine.

I live in a relatively cold place and my heat pump extract heat from the ground. It's worth it where it's cold.

I did a double take on that claim about outdoor temperatures as I've always assumed people were talking about ground source heat pumps.

Judging by how much insulation the typical English house has, it doesn't get cold there.

Not as cold as the Nordics, sure, but depending on cycles, it can drop a few degrees below freezing between November - March

The main issue is that homes were designed to trap and keep heat in, rather than true insulation, which means that as summers get warmer, our homes turn into ovens, with no way to cool them down properly. Case in point last summer with UK temps hitting 40C and above for a few weeks.

Government are trying to kill off the old gas boilers though, with heat pumps being pushed very heavily, not sure if they're enforcing it yet or not though. Apparently they're also looking at switching out natural gas for a hydrogen mix, but that means having to rework a lot of the piping/valves as hydrogen needs much higher standards than currently applied.

With the high summer temperatures (likely to rise further with climate change), I wonder why more people aren't fitting forced air heating/cooling. That would kill two birds with one stone. Even just a simple mini-split system.

The British seems to like to suffer in the heat. Every summer colleagues laugh at me for having AC units, and every summer they start loudly complaining about how hot it is a week or two later.

Yeah, had to get clued up on this for new house in London. A few points:

1. It is unlikely that hydrogen will be pushed heavily by the UK gov because of the expensive pipe rework. The reason they're pushing hard for heat pumps is because of the Glasgow Climate Pact; they're on the hook to reduce carbon emissions or pay heavy fines. To that extent, subsidising heat pumps becomes financially less unviable for them than doing nothing.

2. Regarding the heat in summer; the houses insulate well but don't do much to prevent heat coming in from the windows during summer. There are some pretty useful half-fixes; mvhrs+insulation, or recessed windows/overhangs/sunshades massively aid this. For those who rent that's not much help though :(

Being from Norway but living in the UK: The average UK house is not built for UK temperatures... Insulation here is a bad joke, at least in older housing.

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