[tyho]

> This then leads people to say “heat pumps don’t work” or “heat pumps are expensive to run”, which only feeds into the whole anti net-zero rhetoric.

Tell me, what is the average SCOP of heat pumps in the UK and what is the ratio between the price of electricity and gas?

[tankenmate]

According to the Heat Geek (in the UK) their minimum is 3.5 and their current average is 4.4. I saw a video[0] they did with Urban Plumbers and they visited a new build (well insulated) where the SCOP was 2.2. The main reason it was so low was the heat pump was over specced (by almost 4 times!) and the pump was cycling constantly.

[0] https://www.youtube.com/watch?v=r70Pt6roE0o

[throw0101b]

> The main reason it was so low was the heat pump was over specced (by almost 4 times!) and the pump was cycling constantly.

You can find over-specing in the US/CA as well because of rules of thumb, or installers just looking at what the old system was and replacing it 1:1 with the same new system—never mind that more insulation or better windows have been perhaps put in.

For new builds, a lot of jurisdictions are mandating standardized calculations be done for estimated energy needs, equipment selection, etc:

* https://mrcool.com/blog/understanding-calculations-for-manua...

If you're going to do a retrofit/replacement, it may be worth finding an HVAC company that will do that process for your non-new dwelling. The fact that a company could offer it may mean they're a step above Random Bob's HVAC.

[tankenmate]

I should also note that Heat Geek said, controversially, that one of their biggest indicators of a bad job is companies with more experience as such companies usually had a good reputation along with bad habits. Since customers don't know how these systems work or are expected to perform there is no good feedback mechanism apart from customer not complaining which is less likely as customers don't know what to expect in the way of bills being reduced in a properly working system.

[oliwarner]

Performance numbers from well designed systems aren't relevant to the fears of people who've heard the horror stories.

And there are horror stories from there being too many poorly qualified green installers doing a half-job. Some systems wildly underperform. My octogenarian neighbour had no central heating for two weeks while a replacement pump motor could be sourced and somebody could be found to fit it. You wouldn't have that with gas.

Heat pumps are catching up —I want them to win, we need them to— but this stuff has to get better. Installing one should be certified, performance should be mandated to protect consumers and grant money.

[eru]

> Installing one should be certified, performance should be mandated to protect consumers and grant money.

That seems entirely like a lucrative insurance product that the market could offer. (Just like extended warranties for your electronics.)

I wonder if any actuary is working on it.

[mikewarot]

How is insurance going to provide heat for 2 weeks?

Pay for rental of propane heaters during a cold snap when they're all gone?

Insurance is not the answer here.

[eru]

> Installing one should be certified, performance should be mandated to protect consumers and grant money.

How is a certificate and a mandate that oliwarner suggested going to provide heat? Burning a certificate takes at most a few seconds.

To spell it out for you, the mechanism is pretty much the same as elsewhere:

Companies can offer customers some warranties that their system will work as advertised (ie provide heat with a minimum of fuel). Lots of companies in the private sector offer such warranties on a variety of products. The warranty by itself does not keep you warm, but it typically provides for some restitution in case of failure. (In an extreme case, you can imagine that people would be happy to be paid a million dollars in return for putting up without heat for two weeks. In practice, the warranty will probably settle on something less extreme. For example, some modest monetary compensation plus help with sourcing propane heaters as you suggest. Your imagination is the limit here.)

Because the small companies that do this kind of heat pump installation go bankrupt and disappear all the time, you can administer the warranty via a third party insurance company.

And here's where the certificates come in: just like some car insurance companies give you discounts in return for eg a clean driving record, you would imagine that your heat pump installation company would also be able to purchase much cheaper insurance to benefit their customers if they can provide evidence that they know what they are doing.

In practice the main benefit of the whole scheme would come from insurance companies keeping an eye on the installation companies. The payouts are mostly there to provide discipline and align incentives; but in a well running system the payouts shouldn't be necessary very often.

[ZeroGravitas]

Article on this phenomenon, sometimes called the "spark gap":

https://www.lowcarbonhub.org/p/spark-gap/

The UK is worst in Europe and has been as high as 4.7x recently, more than the average Heat Pump can overcome.

[darkr]

It would only need to be 4.7 to beat a gas/oil system that is 100% efficient.

In reality, a very good gas based system that is well specified and installed might reach 80% as a whole. Most UK gas/oil heating systems are significantly lower.

[mikewarot]

It's not anti-net zero, it's not wanting to freeze to death.

You can't just brush aside the way that actually works that easily.