Heat Pumps, do you have one

[Ballynoes]

Hi,

 

just looking for some real advice.

 

We are soon to start our build, and I hear horror stories, from those who have not built, about Air Source heat pumps, running away with electricity use.

 

Is this real life or scare mongering, most of those who say this do not have a heat pump, but " know someone who knew someone", you get the drift.

 

So my question is, for those who have fitted an Air Source heat pump,  did it run away with electricity or not.

 

I know we will have additional electricity costs, because of the heat pump but we are currently using oil, and I calculate we would need to use an additional 9500KWh each year to be "out of pocket", that's roughly an additional £103 per month of electricity, on top of our current use.

 

Bearing in mind our new house will  have an Air Source heat pump, underfloor heating, and will have U-values of 0.17 W/m2K, according to the spec.

 

I have tried to justify solar panels as well but the sums just don't add up either, taking roughly 23 years to get my investment back.

 

Thanks in advance.

[Jeremy Harris]

We have an ASHP running UFH.  It cost around £2k to install in total, but I did the work myself, so there was no labour involved.  We have significantly more insulation than you, plus pretty reasonable airtightness, and MVHR (the latter makes a pretty significant contribution towards reducing the heating requirements).  The heating cost is tiny, maybe £130/year if that.  We use far more electricity on other stuff, like cooking, charging my car, lighting, ventilation, running the sewage treatment plant and water disinfection system etc.  Our old three bedroom bungalow had gas central heating, running radiators, was around 2/3rds the size of our new house, and cost around £700/year to heat.

[scottishjohn]

20 minutes ago, Ballynoes said:

Hi,

 

just looking for some real advice.

 

We are soon to start our build, and I hear horror stories, from those who have not built, about Air Source heat pumps, running away with electricity use.

 

Is this real life or scare mongering, most of those who say this do not have a heat pump, but " know someone who knew someone", you get the drift.

 

So my question is, for those who have fitted an Air Source heat pump,  did it run away with electricity or not.

 

I know we will have additional electricity costs, because of the heat pump but we are currently using oil, and I calculate we would need to use an additional 9500KWh each year to be "out of pocket", that's roughly an additional £103 per month of electricity, on top of our current use.

 

Bearing in mind our new house will  have an Air Source heat pump, underfloor heating, and will have U-values of 0.17 W/m2K, according to the spec.

 

I have tried to justify solar panels as well but the sums just don't add up either, taking roughly 23 years to get my investment back.

 

Thanks in advance.

thats the thing --your current house

what is the insulation vlaue of its walls and how air tight is it--?????

not good and very draughty I,m guessing 

yes I have one and and wouldn,t use anything else

my guess is the horror stories are from badly installed ones in very poorly insulated houses- 

there will be  dozens  of people on here with ASHP and no one complains of high elec costs compared with  previous systems and or houses

thats one thing about this forum --we don,t just share the good news but the cock ups and mistakes as well

Ifthere was a forum moto it would be

"everyday is a school day "

[Ballynoes]

Hi,

 

thanks for the replies, I suspect ScottishJohn has hit the nail on the head, with people fed up paying for Oil heating and persuaded to fit an ASHP by a salesman, then being surprised that it costs a fortune to heat their still old drafty house.

 

Our new build will be well insulated draft free and have good insulation figures, so I suspect it won't use £1250 per year to heat, as that is what I pay on Oil for my old drafty soon to be demolished house.... can't wait.

 

But I'm still struggling to justify solar panels, so far it will take me 23 years to get a return for a 4Kwh array fitted.

 

No wonder no one fits them any more.

[scottishjohn]

2 minutes ago, Ballynoes said:

Hi,

 

thanks for the replies, I suspect ScottishJohn has hit the nail on the head, with people fed up paying for Oil heating and persuaded to fit an ASHP by a salesman, then being surprised that it costs a fortune to heat their still old drafty house.

 

Our new build will be well insulated draft free and have good insulation figures, so I suspect it won't use £1250 per year to heat, as that is what I pay on Oil for my old drafty soon to be demolished house.... can't wait.

 

But I'm still struggling to justify solar panels, so far it will take me 23 years to get a return for a 4Kwh array fitted.

 

No wonder no one fits them any more.

the way you jusify them is if you can use ALL the power they make --then you are saving 15p per unit agianst the 5p you get selling it back to them 

that is the only way it starts to look sensible at this time -- so that takes a bit of thinking about --but plenty on here are doing that --

sure someone will point you the right way of going about it and get it dsown to 6 -7 years for payback at 23 years the panels are ready for replacing 

 

[joe90]

Like others I have an ASHP (4KW), and with our new well insulated and draught proof house heated by UFH our lecky load is far lower than the same system run on an immersion (temporary solution till the ASHP was installed). Yes I think many people have them set up wrongly/badly in draughty houses.

 

i too can’t justify solar as I won’t live long enough to get my money back ?

Edited October 23, 2019 by joe90

[Jeremy Harris]

1 minute ago, Ballynoes said:

But I'm still struggling to justify solar panels, so far it will take me 23 years to get a return for a 4Kwh array fitted.

 

No wonder no one fits them any more.

 

 

That sounds like a long time, much longer than I'd have expected.  After allowing for the saving in slates, our in-roof PV system cost about £6k or so, for a 6.25kWp system.  We use a bit over 50% of the electricity we generate (maybe a bit more now that I try and charge my car when the sun's shining).  We're on Economy 7, so the daytime electricity price is about 15.5p/kWh.  Our annual generation is about 6,000 kWh, so the value of our ~50% self-use is about 3,000 * £0.155 = £465/year.  It seems that the equivalent of the export payment is now around £0.05/kWh, so the ~50% export would generate another £150/year, making a total of about £615/year in total, so a return on investment of about 10 years.  If I am able to use a bit more self-generation to charge the car, then the return would be a fair bit less than ten years.

[NSS]

4 minutes ago, Ballynoes said:

But I'm still struggling to justify solar panels, so far it will take me 23 years to get a return for a 4Kwh array fitted.

Depends how you're calculating the return. Remember, it's not just the export tariff that you benefit from, but how much of the energy generated you actually use. If you have an ASHP (rather than a gas boiler) you can use the solar generation to power the heat pump and minimise the amount you import from the grid (and the COP of the heat pump will effectively give you circa 3kW output for every 1kW you put into it).

 

 

[scottishjohn]

I,m no expert on solar  PV--but if you had large water buffer tnaks for UFH and DSHW --you could probably use most or all of it to store your electric as hot water and in summer use it to run your ashp as  cooling to the floor --just takes a bit of thinking about -

 

[SteamyTea]

There is a bit of a myth about using ASHPs (or any heat pump) in an old thermally leaky house.

The thermal load, is the thermal load, a heat pump does not care why the load is what it is.

What it really comes down to is sizing correctly.

With a traditional boiler, gas, oil, electric, you work out your maximum load, add a small contingency, they go and buy the nearest size to it, knowing that it can run at full power when it is demanded.

A heat pump, and especially an ASHP, does not work like that.

As you get closer to the maximum output, there is a greater risk of them 'icing up'.  This is because more, damp air is being forced though the unit, just as it is trying to get the biggest temperature difference.

Then what happens is that either/or/and, an electrical resistance element is switched on to help the unit out, the heat pump can 'steal' some of the stored water to heat up the external radiator to defrost it, it can just switch off until it defrosts.  It may e a combination of all of them.

This is why ASHPs have to be oversized to reduce the chance of them running at maximum output and the resistance heater coming on and reducing the chance of frosting.

And that is before the heat emitters have been considered.

Edited October 23, 2019 by SteamyTea

[Onoff]

Just now, SteamyTea said:

There is a bit of a myth about using ASHPs (or any heat pump) in an old thermally leaky house.

 

As in you can or you can't? 

 

Presumably, given the price of electricity it makes sense if using an ASHP to minimise heat losses in the property so it becomes cheaper to run?

 

Would an ASHP be cheaper than oil in a leaky old house (like mine ?).

 

[SteamyTea]

21 minutes ago, Onoff said:

As in you can or you can't? 

You can fit heat pumps to any building, just that because of the oversizing, the capital cost may be higher.

21 minutes ago, Onoff said:

Presumably, given the price of electricity it makes sense if using an ASHP to minimise heat losses in the property so it becomes cheaper to run

That is always the case, regardless of heating system.

21 minutes ago, Onoff said:

Would an ASHP be cheaper than oil in a leaky old house

Possibly, possibly not.  Oil has been pretty cheap the last 12 years or so.  There was a guy, who lives near me, over at the other place, that fitted a GSHP because the price of oil shot up (about 2006/7 I think).

Then the price of oil plummeted and his GSHP cost him more to run than oil.

As a rule of thumb, if people are on mains gas, heat pumps are not financially viable, they may be more environmentally better.  But it does depend on many factors.

If it was simple, we would all know what to do.

Edited October 23, 2019 by SteamyTea

[richi]

Rules of thumb and arm-waving begin:

• Oil costs about 7p/kWh after allowing for boiler efficiency
• ASHP costs about 4p/kWh assuming electricity at 12p/kWh and COP=3

But ASHP runs at lower flow temps, or COP decreases, making cost about the same as oil. So a retrofit is tricky, unless you already have oversized rads.

 

That's my oversimplified way of looking at it, anyway. Happy to be told otherwise.

[Jeremy Harris]

We've recently had similar discussions on relative cost, and I ran some numbers for different fuels and heat sources to provide heating for our house:

 

On 15/07/2019 at 09:18, JSHarris said:

I recently did a running cost comparison, for a typical year for our underfloor heating with different fuels and came up with these figures, which may be of interest (costs include standing charge/LPG tank rental, etc) :

 

LPG fired boiler running UFH = £336.49

 

Peak rate electric boiler running UFH = £329.05

 

Oil fired boiler running UFH = £218.91

 

Off peak (E7) electric boiler running UFH = £206.43

 

Mains gas boiler running UFH = £143.76

 

ASHP at peak peak rate running UFH = £102.87

 

ASHP at off-peak (E7) rate running UFH = £89.25

 

Arguably the standing charge for all the electric heating options should be reduced in proportion to the ratio between heating electricity use and non-heating electricity use, as that standing charge will apply irrespective of the heating system used.  I didn't bother to make that adjustment, but it would tend to reduce the cost of the electric heating options by around £40 p.a. or so if I was to do this.

 

 

 

[Ferdinand]

9 hours ago, joe90 said:

i too can’t justify solar as I won’t live long enough to get my money back ?

 

Believe the MAFIA offer slightly expensive contract options for proving yourself right if that calculation does not work out. ?

 

(Payment would be required in advance)

 

11 hours ago, Ballynoes said:

I have tried to justify solar panels as well but the sums just don't add up either, taking roughly 23 years to get my investment back.

 

You need to think about everything. You can also get and need to think about (you may have done this):

 

- Potentially a saving on roof tiles etc if you go "in roof".

- A partial insurance policy against rising electricity prices (and potentially against policy designed to drive out gas - potentially quite quickly if the rhetoric-over-reality lobby win).

- Similar against potential supply issues.

- Potentially the lecky car saving / ability to start using batteries for short term time shifting if required. But batteries are to a major degree probably dependent on having solar.

- The price of tech may change by the time you build it. eg I would expect the price of solar to fall modestly over the next 2-5 years (I mean 10-20%) after a fall of 70% or so since 2010, but a greater fall in battery prices (maybe) due to tech and scale.

- You could use secondhand panels if you need for some years, or tweak your install otherwise.

- Those numbers will only get better if energy prices increase. Which depends on policy, whether offshore wind lasts, and whether they build any white elephant supply options. (See Tidal Ponds, or perhaps Nuclear). OTOH I can see oil prices falling depending on the level of demand - 25-30% of global oil goes into passenger transport and that will shrink by 95-99% in half a century if we consider ground transport.

- As a temporary factor, it could be argues that current mortgage rates make the finance free or potentially below inflation if you have capacity.

- The spec of your house may change (or not meet or exceed your aspirations).

- It is virtually always possible to reduce the cash cost of anything by 20-40% depending how you do it.

- Finally you may decide to invest for the environment. This was in some measure my motivation.

 

 

Mine are currently probably on a 13-16 year payback, but I jumped before the subsidies were cut, and have a Plan to move half of them to a South Facing roof (2 strings, 19kWp install) when I get my car port / veranda past the management. 

 

I think my call would be to build a long term cost spreadsheet incorporating 200 years of bills to explore options, maybe increase the house spec somewhat, and at least provision for the possibility to do it effectively in future. Then play your best informed game of "spot the ball".

 

 

And remember that there will be wrinkles in the process - this does not apply to you but it is a good example.

 

 

Ferdinand

Edited October 24, 2019 by Ferdinand

[jack]

We have an ASHP and are very happy with it.

 

I'd need to check, but I think our electric bill for the last 12 months was around £900 for everything. That's for a 289m² house in the south of England, U values 0.10 floor, 0.11 roof and 0.12 walls, with 0.6 ACH airtightness, and with us paying very little regard to energy saving behaviour (eg, my wife tumble dries virtually EVERYTHING).

 

We do have 8.5kW of PV, and that will certainly have reduced some of what we take from the grid. During the sunniest months, I suspect we hardly use any energy for water heating during the day. One day I'll get around to measuring some of this stuff!

[SteamyTea]

10 minutes ago, jack said:

last 12 months was around £900 for everything. That's for a 289m² house in the south of England

That is about double what I pay, for a house it is about 6 times bigger.

Though energy use per square metre of floor area is not a very good metric.

[ProDave]

Another one happy with an ASHP. Self installed and not expensive, actually under £1K  Annual heating bill for last year £234 I am hoping that will come down a little as there were a few aspects of the house not complete last winter.  Cost wise they work out similar for mains gas heating prices   So if you previously had a gas bill of £500 per year expect similar for an ASHP don't expect it to be cheaper.

 

Solar PV my DIY installed 4KWp system cost £1500 and by self using £250 of "free" electricity each year it will pay back in 6 years.  I am firmly convinced that is the only way PV is viable now.  If you are paying a company to install it at say £4K then the payback would be 16 years and that is very questionable indeed whether it is worth it.

[Ballynoes]

1 hour ago, ProDave said:

Solar PV my DIY installed 4KWp system cost £1500 and by self using £250 of "free" electricity each year it will pay back in 6 years.  I am firmly convinced that is the only way PV is viable now.  If you are paying a company to install it at say £4K then the payback would be 16 years and that is very questionable indeed whether it is worth it.

 

I'm interested ProDave how you're 4Kw solar system only cost £1500, I have been quoted close to £6500, which makes it un-viable, 

 

At £1500, I would jump at it, did you do it yourself.

 

If I can get the equipment and get the builder to install it whilst he is building the house it might be an option.

 

So far a 500w panel comes in at £400 and I need 8, pus the inventor. 

[dpmiller]

500W panels are very non-standard. Guessing this is a fancy branded odd-sized panel too?

 

270-300W panels are like £100 ea...

[Onoff]

7 hours ago, Ballynoes said:

 

I'm interested ProDave how you're 4Kw solar system only cost £1500, I have been quoted close to £6500, which makes it un-viable, 

 

At £1500, I would jump at it, did you do it yourself.

 

If I can get the equipment and get the builder to install it whilst he is building the house it might be an option.

 

So far a 500w panel comes in at £400 and I need 8, pus the inventor. 

 

Second hand panels, see Dave's thread here:

 

 

[SteamyTea]

500W modules are usually used on large solar farms.  They are about 2 metres by 1.3 meters, and weigh around 35 kg.

[ProDave]

9 hours ago, Ballynoes said:

 

I'm interested ProDave how you're 4Kw solar system only cost £1500, I have been quoted close to £6500, which makes it un-viable, 

 

At £1500, I would jump at it, did you do it yourself.

 

If I can get the equipment and get the builder to install it whilst he is building the house it might be an option.

 

So far a 500w panel comes in at £400 and I need 8, pus the inventor. 

It's all here:

 

 

[Ballynoes]

Thanks, much appreciated.

 

 

[Ballynoes]

Just as a side question,

 

how noisy are ASHP's, as I was hoping to site it outside the house, on the south side, as this gets most of the sun and warmth.

 

Any thoughts. 

 

Edited, sorry should have said directly outside the house.

Edited November 1, 2019 by Ballynoes