Cost to run a Air Source Heat Pump

deantrina

Hi iam looking for some info on my ASHP if anyone can advise . I have a Mutsubushi / Ecodan ASHP with PV panels & UFH which i installed when i done a major refurb 2 years ago . I have been collecting data on the cost for over a year now to see what it is & how it compares to normal heating . I live in the postcode RM14 , just inside the M25 . My floor arae is 252Mts 2 , i have several rooms which are not used so i have heating set down to 10 degrees , other rooms i use - open plane snug / kitchen , 1 bathroom, 2 bedrooms , 1 dressing room ,1 WC room & my electric bill at 6AM in the moring when no TVs etc been on since midnight is now reaching £10 & by bed time its now £23 , cost of my electric is £0.38p / KWH . I have a service being carried out tomorrow to check for problems but very intrested to hear from anyone with same problem or anyone can suggest any ways to reduce costs . Also note my stats are only set to 18 degrees but some rooms only reaching 16 so the UFH just keeps calling for heat as room not switching off , TIA 

ProDave

so £23 per day at £0.38 per kWh is 60kWh of electricity per day.  Not all of that will be the ASHP will it?  but that is still high, 

What sort of house and what was your previous bill with your previous heating system?

deantrina

HI Dave , last 2 days have been virtually the same usage , 75KWA used at a cost of £26.50 . i would guess a very large part of it is the ASHP as we only have a TV & a few lights on the go . It is a semi detatched house over 3 floors as we we have got a bedroom / dressing room in the loft . Unfortunatly before we done the refurb we had a coal boiler that was here when we bought the house so cant compare it to the before iam afraid . I cant even compare it with the electric bill in our previous house as that was 4 years ago when electric was proably £0.07p per KWH. I just cant seem to find any where that i can get some advise about how to manage a ASHP to get the most economical use out of the system . It seems like i have a high electric bill ( from my In Home Display ) weather i have my under floor heating on or off !! . When i get up at 6AM & see the bill for last 6 hrs is £10 i think what is the ASHP doing to use £10 worth of electric !

ProDave

As a comparison, I live in a VERY well insulated house (self build) I use about 50kWh per week heating the house and about 35kWh per week heating the hoy water with my ASHP (ASHP usage individually metered)

My bugbear is I use typically 100kWh per week on "everything else"  so even at this time of the year, my heating usage is smaller than all the other stuff like cooking, washinh machine, fridge televisions etc.  I try to be frugal but just can't get that down.

So perhaps 15kWh of your daily usage is all the other stuff in the house?

You have UFH so the best way to run your ASHP is set the water flow temperature as low as possible, certainly no higher than 40 degrees.  Your HP should be able to independantly set heating water temperature to hot water temperature.  Also set the hot water tank temperature to no more than 50 degrees.  

That might shave some off, but the crux of the issue is likely to be a poorly insulated house.

Rodders53

Read the long threads in the Energy and https://forums.moneysavingexpert.com/categories/lpg-heating-oil-solid-other-fuels sub forums where there are other users of your Ecodan system...

Basic things like ensuring the 'backup' immersion heater is not used to 'boost' CH during the cold weather is advisable - otherwise the advantage of a heat pump producing more heat out vs electric input is lost.   Search for Ecodan on the site to find at least some of those threads!

PLEASE also only use kWH numbers (or as well as cost) as the price of leccy varies over time (months/years) and location (regional pricing) whereas a kWh is a kWh whether electric, gas, kerosene or .....

Ideally this thread needs moving to be more readily seen by others with the Ecodan air to water ASHP systems.

deantrina

ProDave said:

As a comparison, I live in a VERY well insulated house (self build) I use about 50kWh per week heating the house and about 35kWh per week heating the hoy water with my ASHP (ASHP usage individually metered)

My bugbear is I use typically 100kWh per week on "everything else"  so even at this time of the year, my heating usage is smaller than all the other stuff like cooking, washinh machine, fridge televisions etc.  I try to be frugal but just can't get that down.

So perhaps 15kWh of your daily usage is all the other stuff in the house?

You have UFH so the best way to run your ASHP is set the water flow temperature as low as possible, certainly no higher than 40 degrees.  Your HP should be able to independantly set heating water temperature to hot water temperature.  Also set the hot water tank temperature to no more than 50 degrees.  

That might shave some off, but the crux of the issue is likely to be a poorly insulated house.

Dave

good point about the seperate meters i will look into that even if its just so i know what is costing what . I will check the water flow temp tonight to see what that is . Yes the HP can definatly set differant temps for water & heating as i ha to up the hot water temp recently by 2 degrees as bath water not hot enough for winter nights , i thinks its now at 48 degrees . The house is partially 215mm brickwork to front & back elevation but new side wals are full fill cavity & windows all new double glazed , no drafts around doors windows etc. 

deantrina

Rodders53 said:

Read the long threads in the Energy and https://forums.moneysavingexpert.com/categories/lpg-heating-oil-solid-other-fuels sub forums where there are other users of your Ecodan system...

Basic things like ensuring the 'backup' immersion heater is not used to 'boost' CH during the cold weather is advisable - otherwise the advantage of a heat pump producing more heat out vs electric input is lost.   Search for Ecodan on the site to find at least some of those threads!

PLEASE also only use kWH numbers (or as well as cost) as the price of leccy varies over time (months/years) and location (regional pricing) whereas a kWh is a kWh whether electric, gas, kerosene or .....

Ideally this thread needs moving to be more readily seen by others with the Ecodan air to water ASHP systems.

Thanks will take a look & see if i can move this post as you suggest 

anselld

deantrina said:

ProDave said:

As a comparison, I live in a VERY well insulated house (self build) I use about 50kWh per week heating the house and about 35kWh per week heating the hoy water with my ASHP (ASHP usage individually metered)

My bugbear is I use typically 100kWh per week on "everything else"  so even at this time of the year, my heating usage is smaller than all the other stuff like cooking, washinh machine, fridge televisions etc.  I try to be frugal but just can't get that down.

So perhaps 15kWh of your daily usage is all the other stuff in the house?

You have UFH so the best way to run your ASHP is set the water flow temperature as low as possible, certainly no higher than 40 degrees.  Your HP should be able to independantly set heating water temperature to hot water temperature.  Also set the hot water tank temperature to no more than 50 degrees.  

That might shave some off, but the crux of the issue is likely to be a poorly insulated house.

Dave

good point about the seperate meters i will look into that even if its just so i know what is costing what . I will check the water flow temp tonight to see what that is . Yes the HP can definatly set differant temps for water & heating as i ha to up the hot water temp recently by 2 degrees as bath water not hot enough for winter nights , i thinks its now at 48 degrees . The house is partially 215mm brickwork to front & back elevation but new side wals are full fill cavity & windows all new double glazed , no drafts around doors windows etc. 

48 degrees is barely hot enough to prevent legionella.
The bottom line is that ASHP efficiency drops off as the outside temperature gets colder, ie just when you need the most heat.  That is just the laws of physics; you are trying to suck heat out of a very cold source.  So in this weather you are probably not much better off than using a purely electric system.   Obviously insulation improves the baseline whatever the heating system.

subjecttocontract

Is your ASHP an air to air or  air to water system ?

ProDave

anselld said:

deantrina said:

ProDave said:

As a comparison, I live in a VERY well insulated house (self build) I use about 50kWh per week heating the house and about 35kWh per week heating the hoy water with my ASHP (ASHP usage individually metered)

My bugbear is I use typically 100kWh per week on "everything else"  so even at this time of the year, my heating usage is smaller than all the other stuff like cooking, washinh machine, fridge televisions etc.  I try to be frugal but just can't get that down.

So perhaps 15kWh of your daily usage is all the other stuff in the house?

You have UFH so the best way to run your ASHP is set the water flow temperature as low as possible, certainly no higher than 40 degrees.  Your HP should be able to independantly set heating water temperature to hot water temperature.  Also set the hot water tank temperature to no more than 50 degrees.  

That might shave some off, but the crux of the issue is likely to be a poorly insulated house.

Dave

good point about the seperate meters i will look into that even if its just so i know what is costing what . I will check the water flow temp tonight to see what that is . Yes the HP can definatly set differant temps for water & heating as i ha to up the hot water temp recently by 2 degrees as bath water not hot enough for winter nights , i thinks its now at 48 degrees . The house is partially 215mm brickwork to front & back elevation but new side wals are full fill cavity & windows all new double glazed , no drafts around doors windows etc. 

48 degrees is barely hot enough to prevent legionella.

Several sources say if you have a sealed unvented hot water tank and it is fed by treated mains water, then there is no need for heating any hotter as no bugs can enter the water.

Only required if you are on a private water supply or have an old vented hot water tank fed from a header tank in the loft.

Mutton_Geoff

deantrina said:

Hi iam looking for some info on my ASHP if anyone can advise . I have a Mutsubushi / Ecodan ASHP with PV panels & UFH which i installed when i done a major refurb 2 years ago . I have been collecting data on the cost for over a year now to see what it is & how it compares to normal heating . I live in the postcode RM14 , just inside the M25 . My floor arae is 252Mts 2 , i have several rooms which are not used so i have heating set down to 10 degrees , other rooms i use - open plane snug / kitchen , 1 bathroom, 2 bedrooms , 1 dressing room ,1 WC room & my electric bill at 6AM in the moring when no TVs etc been on since midnight is now reaching £10 & by bed time its now £23 , cost of my electric is £0.38p / KWH . I have a service being carried out tomorrow to check for problems but very intrested to hear from anyone with same problem or anyone can suggest any ways to reduce costs . Also note my stats are only set to 18 degrees but some rooms only reaching 16 so the UFH just keeps calling for heat as room not switching off , TIA 

How insulated is your house? With ASHP systems you have to change your mindset on how to run your heating. Initial call for heat causes the HP to run at a higher more expensive rate (Samsung). It's not efficient to set start stop times for the heating nor have unused rooms within the fabric of your house that cold as internal walls are not usually insulated.

Mine is set never to go below 18C with programmed lifts in the temp to 20C for living/bedrooms at appropriate times of the day. My UFH has a zone and corresponding stat for every room. The house did get cold last year after a minor fault (blocked water filter) and it took 3 days to warm it all up again.

Once the temperature gradient is reduced, the ASHP runs more economically.

The heating water is heated to 45C, the HW cylinder to 50C and the system has an anti legionnaires function where it runs the immersion once a week up to 65C. This is set within the Samsung controller.