General > General Technical Chat
What is the real story around heat pumps?
tom66:
Can legionella even grow in a hot water tank? The majority of modern hot water tanks, at least in the UK, are unvented with external expansion vessels, as this tends to be more efficient. Since the vessel is under pressure, essentially the entire volume is full of water. Legionella is not an anaerobic bacterium, so the chances of the bacteria even having a location in which to grow is questionable. I suppose it would be a concern for a vented system, but in the UK those haven't been installed for 20+ years.
pcprogrammer:
--- Quote from: Siwastaja on February 24, 2024, 09:31:32 am ---
--- Quote from: pcprogrammer on February 24, 2024, 09:03:32 am ---The whole idea of these systems to pay for themselves is kind of bullshit. Sure it can reduce on your energy bill, but it will still cost money. Depending on the type of system and the cost to install it can take a long time before any savings start to come.
--- End quote ---
Remember that expensive systems such as quoted for you are a kind of specialty of wealthy societies and wealthy households. Energy solutions are being sold exceeding their true value, because there is market for that and people still buy. My air-to-water heat pump installation was less than 4000EUR all parts included, although I did the install work myself but it would have been less than 1000EUR for work if I just paid for hourly rates for electrician and plumber; and the end result is way better than how a typical 15000EUR complete one size fits all solution would have been.
Typical cost for air-to-water retrofit was around 8000-9000 EUR here but nearly doubled to 14-15000 EUR almost overnight after a 4000EUR subsidy come into place. The market does not reflect actual costs, and any subsidies further twist the market. Enough people are willing to pay outrageous prices when they feel good about it.
In Japan air-to-air heatpump costs something like 500EUR installed so one can easily afford one per each room. They do pay back for themselves, that's literally why they were developed in 1980's in the first place, to save cost of fossil fuels.
--- End quote ---
Even when I would get a cheap monoblock heat pump and do the work myself and spend say the 4000 euro you mentioned yours costed, it would still take a very long time to see a so called "return on investment" or reach a break even point.
What I pay now for my heating is 24m3 of fire wood at 55 euro the m3 is 1320 euro.
On average loss of interest on 4000 euro in a savings account lets say 80 euro. (At the moment we get more then 2% here in France, but it will vary)
Needed heat energy 16500KWh at SCOP 3.5 is ~4714KWh at an average electricity price of 20 euro cents comes to 942,8 euro.
So saving comes down to 1320 - 942,8 - 80 = 297,2 euro per year so comes down to about 13,5 years. At that time it might be needed to buy and install a new heat pump. If not you will have to save up the money you save and it will take another 10 years, with interest on interest, or so to get the initial 4000 euro back in the bank.
This is not taking into account the cost of owner ship like maintenance or replacing defective parts if needed, nor is it taking into account the rise in electricity price that comes round once in a while. The latter would also effect the price of fire wood, so not really needed to adjust for.
And that is why I said that living costs money.
It might be different for others who have much higher heating costs with their current system, but still you will never really get your investment back.
To me there is a distinction between saving money and making money. With PV solar panels it might be a different story when you harvest way more energy than you consume and can actually sell the remainder to the energy company. But then still you have to take cost of owner ship into account.
Someone:
--- Quote from: Zero999 on February 24, 2024, 11:20:56 am ---
--- Quote from: Someone on February 24, 2024, 11:10:47 am ---All it needs is people plainly stating the reason why they think their position, instead of non specific unarguable generalisations.
Most of this thread is UK people dodging the fact that their energy costs are abnormal, while making all sorts of big claims about the rest of the world. Obnoxious colonialism vibes.
--- End quote ---
And from my position, I see this thread as a load of Europeans lecturing us Brits telling us what to do.
--- End quote ---
Quite the reverse from my perspective. You (and others) are jumping onto worldwide generalisations (as applicable to the OP) and arguing (without stating clearly that it only applies to your local situation) that other assessments/positions/choices are wrong.
...and coming back time and time again without citations, references, or bothering to make basic factual checks on your posts. Oh yeah, thats obnoxious.
zilp is putting up some pretty convincing rational arguments for heat pumps even in the UK. Which agree with my simple statements earlier:
--- Quote from: Someone on February 21, 2024, 08:45:49 pm ---Given the uses of gas a realistic price ratio is heading somewhere closer to 1:2, many countries are already there and betting on cheap gas being either:
a) available in other locations, or
b) continuing the large price ratio into the future
are both unrealistic.
--- End quote ---
If gas is so cheap in your market that heat pumps aren't economic for domestic heating, then why isn't someone bottling it up and selling it off to other countries for profit? Why aren't gas power stations running at high utilisation and profiting? Other countries are way ahead on the gas market changing, it's unrealistic to think the UK (or any other country) can maintain such large price ratios on an ongoing basis.
tom66:
--- Quote from: pcprogrammer on February 24, 2024, 08:24:16 pm ---Even when I would get a cheap monoblock heat pump and do the work myself and spend say the 4000 euro you mentioned yours costed, it would still take a very long time to see a so called "return on investment" or reach a break even point. [...]
--- End quote ---
True if you just consider the outright cost of the heat pump, BUT, if you instead install the heat pump when the existing heating system needs refurbishment or replacement (do you have a wood/biomass boiler heating hot water for the house for instance?) then it makes a lot more sense economically since you are just paying the "premium" to get one. Say in my case, a replacement gas boiler costs around £2,500 to have fitted professionally. If I could get a heatpump fitted for about £5,000, then I only have to make up £2,500 in heating costs over a decade, ignoring for now the time value of money. That seems just about feasible - £250 per year in savings (I spend roughly £1,200 a year in gas) or about 20%. If combined with solar/battery and load shifting (not heating the house at peak times and using a tariff that gives me a discount for doing so) then it probably ends up more cost effective.
I can get an install for under £5,000 if I use the grant scheme, but the real cost to the taxpayer is another £7,500. Such a system would have a 7 year warranty as long as it is serviced, which is good but not amazing, though better than most gas boilers which tend to have only 2-3 year warranty at best as they are so commoditised now. What worries me is between year 7 - say the end of the life of the system at year 12 if indeed it has failed by then. Do I go for another heat pump? Will costs have fallen by then to be similar to gas boilers? Or will it instead cost £5,000 to have the heat pump unit changed? If that is the case, the economics don't work out against gas.
Someone:
--- Quote from: tom66 on February 24, 2024, 08:07:52 pm ---Can legionella even grow in a hot water tank? The majority of modern hot water tanks, at least in the UK, are unvented with external expansion vessels, as this tends to be more efficient. Since the vessel is under pressure, essentially the entire volume is full of water. Legionella is not an anaerobic bacterium, so the chances of the bacteria even having a location in which to grow is questionable.
--- End quote ---
Still a problem and while deoxygenation is theoretically possible I've not heard of it being commercially used:
https://doi.org/10.3390/w14172644
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