Heat pump experiences

[rogerzilla]

I believe a stored hot water system is now considered slightly more efficient than a combi. Yes, there are heat losses from the cylinder (an issue all heat pump systems have as well) but conventional boilers have burners that are more optimally sized for efficiency. Combis need to be able to kick out tens of kilowatts for instantaneous water heating, and the big burner doesn't efficiently modulate down to 5kW or whatever a steady heating demand might be.

 

[mjr]

A friend had a air-source pump fitted and his electric bill is now £170 a week!

Something is broken. You can achieve a similar result with gas by drilling a hole through the supply pipe, or something to that effect. At least broken heat pumps rarely go boom and blow the house down.

 

[mjr]

The highest flow temperature you're likely to get with a heat pump is 55°C,

The 1950s called and want that heat pump back. Many go hotter now, but few people want their hot water to be a scald danger at the tap and anything above 50 kills Legionella when the tank insulation means it stays that hot for hours. The heating loop is run cooler but that's a sealed system with additives, not something you should be inhaling anyway.

What scares me most about heat pumps is the supposed necessity of running them 24/7 to keep the house warm, because their output is too low to raise a house from cold in any reasonable time.

A common misunderstanding! The ASHP controller is left on 24x7, rather than the bad old timeswitches commonly used with overpowered fossil systems, but it will only run the pump continuously when it's below the design temperature (-3°c is common) for a prolonged time and that's rare. Even then, it is possible to boost heat if needed, it just costs more. It's not as quick to lift the temperature as an oversize combi but that's massively inefficient all the time anyway.

I want a cold house at night or if I'm out. People who see big savings were probably heating the house 24/7 on gas too, rather than just for 4-5 hours in the evening.

Our oil heating used to be on maybe 2 hours mornings and 3 or 4 evenings. The ASHP controller doing what it wants all day is cheaper and we almost never have to think about pressing buttons.

 

[Drago]

...when the tank insulation means it stays that hot for hours.

Days, in fact. Shut it all down while we went way and the water was still hot enough for a proper "hot" shower more than 4 days later.

 

[gzoom]

That's astonishing


No, his name's Charlie and his house is at the end of Bird Cage walk😁
In all seriousness though, £170 is 680kWh of electricity if he were paying the max. Thats 100kW a day so something is amiss...

We have solar panels, home battery, and EV. We looked into a heat pump very seriously during our major house renovations, given this was what the house looked like at one point, we had every opportunity to go down the ASHP route, including enough garden space for GSHP.

However after lots of research and talking to some ASHP installers I'm 100% GLAD we stuck with gas!!! Heat pumps DON'T reduce the heating requirements of any house, all they do is shift the energy use from gas to electricity.

Our gas usage for the first 2 months of year is averaging out at 162kWh per day, it you assume a heat pump has a real world efficiency of 3:1 versus gas we would be using 54kWh of electricity per day. As you can see our electricity usage over the same period is around 36kWh per day, so if we had a heat pump instead of gas our total consumption is just shy of 100kWh electricity per day.

Our gas costs are essentially the same as electricity costs needed if we had a heat pump, so there is no money saving to be had going with a heat pump versus gas.

From what I also understand heat pumps require time and attention to get the system running well, drop the 3:1 efficiency down to 2:1 and all of a sudden a heat pump will be MORE expensive than gas. So more complicated and more expensive, no thank you, and its why we stuck with gas.

The biggest cost saving we could have made to heating to was improve the thermal efficiency of the house and not have some 60sq meter of new glazing added to the house without increasing the footprint.

However we love the light provided by full floor to celling glazing would 100% have the same amount (if not even more) glazing for the next build project , by than I suspect we would be forced to have an ASHP, and will be speccing some big home batteries at the same time to load shift electricity use to cheaper rates .

.....oh I forgot we do have some Air to Air heat pumps, both bedrooms upstairs have them. But they use a measurable amount of electricity to produce heat, and with no real solar PV generation in winter we are using the gas boiler to help heat the bedrooms. Come summer though they will be very handy to keep temperatures in check, and should be 'free' to run with solar PVs providing power.

 

[gzoom]

and also

it is quite common for us to have the heating off all day and the windows open
then just stick the heating on for an hour or so in the late evening to keep the lounge warm

sounds like we would need to put the fire on - which then eats power

Don't you mean wood? Recent storms bought down a small tree in the garden, should have enough wood for next Xmas.

We actually have UFH in the living room that has the fire, but the stove brings a much nicer/warmer feeling to the room.

So actually we have all the common sources of heating used in the house, heat pumps, gas boiler and solid fuel, taking into account all different experiences is important .

Solid fuel actually 'feels' the nicest but is the biggest effort, wet UFH however you power it is the best for actual heating, but some kind of air temperature control is also pretty important in the summer.

I guess that's why in the US heat pumps are used far more than the UK, if your house is set up for ducted air heating, essentially a massive AC/heat pump will let you heat and cool with the same system. The energy usage must be astronomical though!!! US housing stock I suspect is worse than the UK for insulation.

 

[mjr]

Heat pumps DON'T reduce the heating requirements of any house, all they do is shift the energy use from gas to electricity.

Basically true, but it does also remove a source of air pollution and massively increase efficiency.

From what I also understand heat pumps require time and attention to get the system running well, drop the 3:1 efficiency down to 2:1 and all of a sudden a heat pump will be MORE expensive than gas. So more complicated and more expensive, no thank you, and its why we stuck with gas.

You'd get 3:1 with any correctly installed system. A year of attention and you get things like the almost 5:1 of that extreme setup in the video a few pages ago.

The costs should change. The green taxes should move to gas, gas will run out anyway and the network maintenance costs will be shared between fewer and fewer users.

 

[gzoom]

Basically true, but it does also remove a source of air pollution and massively increase efficiency.


You'd get 3:1 with any correctly installed system. A year of attention and you get things like the almost 5:1 of that extreme setup in the video a few pages ago.

The costs should change. The green taxes should move to gas, gas will run out anyway and the network maintenance costs will be shared between fewer and fewer users.

I'm 100% sure we will not run out of fossil fuel in my life time.

 

[mjr]

I'm 100% sure we will not run out of fossil fuel in my life time.

We will never quite run out of fossil fuel. It'll just get more and more expensive.

 

[Drago]

Or it may not. As resources dwindle so will demand.

The oil industry likes prices around the $75 dollar a barrel mark. There's enough there for a nice profit, but not enough that people feel financially pressured into using less of it, and they'll do everything within their power to maintain pricing levels in that sweet spot.

 

[rogerzilla]

Heat pumps could be good but they need to be able to produce higher-grade heat to suit more homes, be physically smaller, and far more established and trusted. Currently there is a high chance of getting a poor installation and parts and service availability are patchy. There are stories of fairly new pumps being scrapped because the manufacturer can't supply spares (Mitsubushi was one).

Compare that to a gas boiler. Most easily do 15 years, even the condensing type, and a man will turn up and fix it on the same day if it breaks down. You have to be that good.

 

[Marchrider]

I'm 100% sure we will not run out of fossil fuel in my life time.

We have enough fossil fuels for the next 1000 years - problem is if we burn the lot we will have around 15°c of global warming - there will be some amount of chaos - and we will never stop burning it - LOL - stupid humans

 

[mjr]

Heat pumps could be good but they need to be able to produce higher-grade heat to suit more homes,

I don't understand the relevance to home heating. Grades of heat seems to be something to do with climate change and racial bias in US cities. Can you explain what this has to do with heat pumps, please?

be physically smaller, and far more established and trusted. Currently there is a high chance of getting a poor installation and parts and service availability are patchy. There are stories of fairly new pumps being scrapped because the manufacturer can't supply spares (Mitsubushi was one).

Other than the physical size, which will be difficult to reduce without penalty because bigger collector means more efficient means cheaper, I'm really not sure that's much different to any heating system. I've certainly encountered very poor servicing for gas boilers, especially in rented accommodation managed for an investor-landlord by a local agent. Maybe you own your house and have found an installer/servicer you trust who you keep going back to, but that's not the average experience.

One difference with heat pumps is that retrofits for other systems are much rarer and faults with the heating systems in new-builds are dealt with as faults in the original building. There are stories of fairly new gas boilers being scrapped because spares become unavailable, sometimes because the developer got some end-of-line models at a discount to do the whole estate.

I guess another is that the grant-assistance of many heat pump installations means that most people so far had to find a new installer who meets the certification requirements of the grant scheme, and that certification definitely doesn't ensure excellence any more than every Corgi-registered gas fitter was excellent. Just basic competence in that they shouldn't risk blowing too many homes up without being found out and deregistered!

Compare that to a gas boiler. Most easily do 15 years, even the condensing type, and a man will turn up and fix it on the same day if it breaks down. You have to be that good.

Anyone who has ever spent a cold night waiting for the servicer to get spares (as I have) will be laughing a hollow laugh now. Gas boilers have been so unreliable in reality that several manufacturers are now having to offer 10-year guarantees to shift them, and quite often those guarantees aren't backed by insurance so are worthless if the manufacturer exits the market, like so many before them have: remember Thorn or Camray? Ideal and Glowworm got bought and the original company wound up.

Anyway, spares and repairs are a problem but far from unique to heat pumps.

 

[rogerzilla]

British Gas Homecare. They just turn up and fix your gas boiler.

By grade of heat you can assume I mean flow temperature, although it's a bit more complicated than that. For instance, you can't have a combi heat pump because there is no high temperature, high output source.

 

[mjr]

British Gas Homecare. They just turn up and fix your gas boiler.

...turn up same day 80% of the time, according to (checks notes) British Gas HomeCare. No figure on what % they fix but it must be below 80. https://www.britishgas.co.uk/cover/boiler-and-heating.html

By grade of heat you can assume I mean flow temperature, although it's a bit more complicated than that. For instance, you can't have a combi heat pump because there is no high temperature, high output source.

Are you just redefining terms?

Combi-like behaviour is not required to suit many times. After all, it didn't used to be an option before artificially cheap North Sea Gas.