# How to bring down running cost of heat pump? Help!



## record (29 Nov 2008)

I have a heat pump that uses an air-to-water heat source. This is my first year using the system, but the running costs are astronomical!

I have been keeping a daily record of nighttime / daytime ESB units used. On average, I'm using 30 units during the day, and 35 at night. This costs me a total of about €9 per day! Yesterday, things went out of hand when the daily running cost went as high as €13. (I know the outside temp also fell, but this is crazy stuff.)

I understood that the cost of running the system would be about €2 per day, but even if that was out by 100%, I'm still way over what the costs should be.

The system is set up so that it makes best use of the night-time rates, I have had the engineer who fitted the system out to check it out, but to no avail. At this rate, I'd be far better just getting in an oil-burning boiler.

Some fact on my house - 3,000 sq. foot, well insulated, underfloor heating downstairs, rads upstairs (hardly ever turned on). UFH set for 21 degrees at night and 17 degrees during the day.

Any suggestions would be much appreciated!


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## tick tock (29 Nov 2008)

are the stats left on all the time...


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## 10to1 (29 Nov 2008)

I wouldn't have thought €9/day was high for a 3000 sq. ft. home for an aerothermal system. Is this an direct or indirect system? What co-efficient do the product suppliers claim?


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## Mr Tayto (29 Nov 2008)

Hi Record

   Was your unit sized correctly, ie was the theoretical demand calculated. The days of sizing a heat source by the sq footage are long gone. From my past experiance with suppliers the norm with all primary heat sources was to over size the unit, thinking a warm customer was a happy customer, but with improvements in building regs and an understanding of the value of airtightness this has at long last changed.
e9 a day is definitely a lot to pay. I would be talking to the installer of the unit, ensure all stats are working, maybe install data loggers to monitor the output trends v demand.


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## record (29 Nov 2008)

Thanks very much for the replies.



tick tock said:


> are the stats left on all the time...


 
I'm not sure how to answer that. They are set as follows:

11pm - 7am: 21 degrees

7am - 11pm: 17 degrees.

As I understand it, that means that they only call for heat during the night (i.e. when the room temp falls below 21). As the room temp never falls below 17, they don't call for heat during the day.



10to1 said:


> I wouldn't have thought €9/day was high for a 3000 sq. ft. home for an aerothermal system. Is this an direct or indirect system? What co-efficient do the product suppliers claim?


 
Re €9 per day - I suppose I'm basing my feeling that it is too high on the fact that the installer reckoned it would cost about €2 per day. (By the way, I bought the house after the system was installed, so it isn't like he was trying to convince me of this low cost just to get a sale).

A direct or indirect system? What co-efficient do the product suppliers claim? I'm afraid I don't know what these terms mean. Could you explain?



Mr. Tayto said:


> I would be talking to the installer of the unit, ensure all stats are working, maybe install data loggers to monitor the output trends v demand.


 
The stats seem to be doing what they should be doing, but I'll get them checked anyway. Where would data loggers be installed?


By the way, I also notice that over the last two days (when the outside temp is just 2 degrees), the system is having trouble getting the rooms up to a confortable temperature (i.e. 20 degrees or above).


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## Mr Tayto (29 Nov 2008)

> Where would data loggers be installed?


In series with the heat pump supply with references in each zone. Your supplier or the manufacturer will be able to help you with this.



> the system is having trouble getting the rooms up to a confortable temperature (i.e. 20 degrees or above).


This sounds like the unit is either undersized or you have a lot of drafts, ie the heat is escaping and the pump cant keep up.


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## olddog (1 Dec 2008)

The manufacturer of the *air to water *heat pump that you have will have speced a COP figure for the unit ( I would guess its about 3 - i.e. for every kW of electricity it uses it produces 3kW of heat ).

The quoted COP figure is usually based on an external air temperature of 7C

As the external air temperature decreases the effective COP figure decreases.

Some manufacturers publish graphs of COP vs external air temp. Perhaps there is one available for your unit ?

I would *guess* that for an external air temperature of 0C the COP figure would be around 70% of the figure for 7C

So, put together the fact that your house needs more heat of late because its been very cold outside and the fact that the efficiency of the heat pump decreases as the external air temperature decreases you should expect the heating electricity consumption to have increased significantly

HTH

Olddog


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## dj01 (1 Dec 2008)

Hi record,

We recently finished our house which is also 3,000 sq ft and we installed an Thermia Atria air to water heat system with UF throughout. We are not long in the house, so have only got one ESB bill to date, which was €220. That was for about 3-4 months as it covered from usage from first connection. 

So i can't really get a true handle of the running costs until we get a few more bills. Havn't checked, but will have a look at the meter to see how many units we're using. I have our's setup very similar to yours, but have it programemd to run at 22 degrees for 5 hours during the day with a set back to 17 for the rest of the time. We've also got a night meter installed. 

But your runnings costs seems far too high, as we too bought the system on the basis that over a year it would be cheaper to run that oil. 

What have your montly bills come in at on average? Have you double checked with the ESB that they definately have you on a night meter tarriff? How many people are in the house, e.g. is there a high usage of hot water and electricity in general that could be adding to your bills? What make is the system?

Will keep you posted on our next bill as a comparison if it helps


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## record (1 Dec 2008)

Old Dog: Thanks very much for the info re the COP, I'll look into that a bit more. I've done a brief internet search and there is indeed a graph showing the COP Vs outside temperatures, I'll just need to check the exact model of my air-to-water unit.



dj01 said:


> What have your montly bills come in at on average? Have you double checked with the ESB that they definately have you on a night meter tarriff?


 
Just moved into the house over the summer. Our ESB bill for September - October was €480. I'm definitely on the right tarriff with the ESB.



dj01 said:


> How many people are in the house, e.g. is there a high usage of hot water and electricity in general that could be adding to your bills?


 
The are 2 adults and young kids in the house, I wouldn't say we over-use the hot water / heating if you know what I mean (no nightly baths, etc.). About 1 dishwasher load (economy setting) every 2 days, similar for washing machine. No widescreen TVs / heavy computer use, etc.



dj01 said:


> What make is the system?


 
The system is Alpha-Innotec, from what I read online about them it seems to be a fairly good system, my theory is that are problems with its settings or with the way it was installed.



dj01 said:


> Will keep you posted on our next bill as a comparison if it helps


 
I'd be very interested to hear what your next bill come in at.

Many thanks for your reply.


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## geothermal (10 Dec 2010)

hi i have ground-source  heat pump with 3 years, 1800 sq feet includes hot water and heating,  bedrooms 18 degrees, kitchen dining living room area 21 degrees, average bill over 12 months is 70 euros a month. it is all down to settings there is so many settings but when you get them right it is the cheapest form of heating, i am still tweaking it after 3 years and i think i have found a way to make it cheaper the last few days. i do not understand how your heat-source works .


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## Leo (10 Dec 2010)

Thead is 2 years old, OP may no longe be active.


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## geothermal (11 Dec 2010)

ok i thought there might be some response. hopeing  to hear other peoples views and running costs on ground-source heat pumps. thanks


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## orlao (31 Dec 2010)

Hi, we've got geothermal ground heat source pump, just got our Airtricity bill, has been estimated, but we've estimated the true cost for the past few months to be €520 which is just astronomical. I know we've had very severe weather, but we can't afford that. We need to find out whether there is something we can do. 
From info we got at the time of installation it is Climatemaster Heat Pump MP004/2.3 (10kw@-3%) single phase dual compressor unit. Ground collector system of 5 x 150m hydrodare, twin 10 unit collector manifold. Don't know if that means much. 
We have about 2800sq ft house with underfloor heating on two floors. The system is about 7 yrs old. We are wondering whether we should have the system turned off during the day as it's the day costs which are racking up the bill. And the system didn't keep the house warm during the recent cold spell, only for our two wood burning stoves we'd have been going around in duvets all day. Do geothermal heat pump users only have their system kicking in at night. One friend had a quick look and said our system is too small for the size of the house, the company which installed it (based in Kilkenny) has now gone. We were told at the time it was more than enough. Would appreciate thoughts and tips from any other geothermal users.


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## esox (1 Jan 2011)

leo do you think record could be contacted would be interesting to see how the original op got on with the geo system


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## Leo (4 Jan 2011)

Hi Esox,

They were actve up to a couple of months ago anyway, so you could send them a PM. Sending them a PM will send a notice to their contact email address, so include a link to this thread to make them aware of the outstanding question.
Leo


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## esox (9 Jan 2011)

sent pm to record, we'll  just wait and see. love to see how the geo works out after 2 yrs


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## jgm (30 Jan 2011)

Hi Geothermal

I have a Waterkotte 11.2kw heatpump installed with 2 x 120metre boreholes, in a new house 3500 sq ft, good standard of insulation, have heatpump timed to come on at 6pm and off at 7pm, return temp to heatpump set at 21 degrees, no stats in living areas, no buffer tank, system operates on 2/3rds of flooring open constantly. stats in bedrooms set at 19 deg ( used mainly as a gadget had to have something) For the last week of January 11, outside temp at night 0 degs approx. heatpump runs for approx 4 hours, ( I measure the operating hours daily) Im not sure what this calculates at but I thing the pump is using 3.2Kw  X 4 hours = 13 kw ie 13 units at average of 20cent per unit ( I have night rate meter) is 2euro 60 cent per day. My installer recommeds leaveing heatpump running 24/7 but I am happy with my settings on this. By the way i have plenty of heat all day. House does not cool down. What are your views on my set-up.


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## record (31 Jan 2011)

esox said:


> leo do you think record could be contacted would be interesting to see how the original op got on with the geo system


 

Just saw the query now, so sorry for delay in getting back to you.

*Costs of heatpump (air-to-water):*

The most recent figures I have are as follows:
2009 €1,900 (total electricity cost)
2010 €1,800 (total electricity cost)​These figures include 'normal' electricity costs. In addition, in late 2009 we got an oil boiler fitted as a backup heat source. We spent about €400 on oil in 2010.

As such, taking 'normal' electricity usage out of the costs, I estimate our fuel bill to be around *€1,500 / €1,600 per annum*. (Our house is 3000 sq. ft. / 290 sq. mt., good but not great level of insulation, no MHRV.)

*Problems with heatpump:*
We have been unfortunate to have had ongoing problems with our heatpump. These problems stem from bad design and fitting of the system. From talking to SEAI, and from reading other threads here, this seems to be a very common scenario. I think we are nearly getting to the stage where all the problems have been sorted out, but it has been a real pain to be honest.

*Conclusion:*



Would I recommend a heatpump? A qualified yes:

It is an efficient way to heat a house.
It gives a very comfortable heat.
Clearly, it must be fitted by someone who knows what they are doing. However, this condition is very hard to meet, and it is very hard to know if the person knows what they are doing.
The house must be a low energy house for the system to be totally efficient. Irish house building leaves a lot to be desired in this regard.
The system must be backed up by a secondary heat source, such as a condensor oil boiler.
In addition to that, something like a room-heating stove is needed for quick bursts of heat when needed (as there is an inherent delayed reaction with underfloor heating).
If I was doing it all again, I would spend most of my money on efficient house design and tons of insulation, so as to minimise ongoing heating costs. If this is done, a fancy heating system is not needed.


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