Daikin Altherma monobloc running cost December 22 cold spell

[GHDirect]

Hi all.

I think my title states my issues, that this months ASHP KWH consumption costs are becoming a joke.

I thought I would check with the forum and users who support this technology as to whether mine is the norm or I am missing something in running efficiently.

 

Bit of background.

I built the 155sq Mtr + garage 3 bedroom bungalow using traditional material over past 8 years and mostly myself.

Exposed country location, block beam floor + screed + tiled, brick outside, cavity therm walls insulated, therm walls throughout, d/glazed throughout, tiled pitched roof, intergal garage (36 sq mtrs) good helping of insulation to floor, wall roof etc.

An MCS registered company designed and supplied me with all the material to install Daikin Altherma 7KW ASHP, UFH with stat to every room + Daikin 300ltre hot water tank. Which I did with controls in garage area.

This company never visited the final install, but have to say their drawings, telephone and install support was excellent.

Daikin attended, were positive about the install and set it all up in 2018.

Since then except for a main PCB/fan failure it is left to run 7 x 24 with just Daikin annual maintenance.

 

Since instalation and living in the property past 3 years my annual KWH consumption for whole has been in excess of 14500 P.Annum but unable to accurately know how much the system was consuming.

Hot water set to 48 deg, most rooms and hallway are set to 20 deg except for spouse main bedroom at 22 deg (she is disalbed with serious heart condition so need that heat).

I don't fiddle with it or alter the stats and it runs 24 x 7 year round.

 

November 22 I fitted a consumption meter to the electric feed tails that supply the ASHP, Immersion and its logic.

I can now accuratly check its KW consumption.

Accepting November it began to get colder the system average consumption showed 24 KWH per day.

Dec we have seen it cold past 10 days being -4  to -7 so the system has been flat out 24 x 7 some of it defrost time.

It has managed to meet the stat settins but the electric consumption during these days has been frightening.

Yesterday 14th Dec being -7 outside it consumed 75 KWH

Yes its a cold snap, but his technology is encouraged around UK but mine doesn't perform.

Meanwhile I have since shut down two areas and dropped 4 of room stats a degree to see if it drops electric consumption difference.

 

I know there are members out there that love all this stuff so feedback welcomed.

 

I can access the Daikin control panel in installer mode but no expert.

 

G H Direct

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[ReedRichards]

I think you may be overreacting.  If your heat pump keeps your house warm then it is doing its job and performing.  It will use a lot of power in unusually cold weather and make up for this in spring and autumn by using much less power.  Whether the economy of operation is good or bad depends on the heat loss from your property.  The company that supplied your heat pump presumably made an assessment of this.  It would give a context with which to assess your electricity use.  

[Kelvin]

You can’t judge it on the coldest week of the year just like you wouldn’t say it costs next to nothing to run in the warmest week of the year. 

[jack]

45 minutes ago, Kelvin said:

You can’t judge it on the coldest week of the year just like you wouldn’t say it costs next to nothing to run in the warmest week of the year. 

Around my way (Hampshire/Surrey borders), the odd overnight sub-zero low isn't unusual, but I'd generally make a comment to the missus if -3 or -4 were forecast.

 

This last week, overnight temps have consistently been in the -5 to -7 range, with daytime temps no higher than 3 degrees (and regularly lower - don't think it got above 1 yesterday). The average temperature for the whole week will almost certainly be well below zero, which is unheard of in the 14 years I've lived here.

 

So yes, not an ideal week to assess anything other than perhaps worst-case figures!

[Radian]

1 hour ago, GHDirect said:

Yesterday 14th Dec being -7 outside it consumed 75 KWH

COP might be somewhere around 2 point something so 150kWh of heat, supplying HW as well doesn't sound implausible. Have you got a heat loss calculation for the house? If it was mine I'd have been pleased with that performance (admittedly a bigger house).

[GHDirect]

Hi all.

Thanks for the replies.

I have also read the other postings about ASHP in this cold snap.

I requested a system that would perform below zero and this is struggling.

To me this cold snap below zero is the only time to prove that part of design.

 

The Daikin controller software has pages of setup one being "weather dependant"

It ocurred to me that this option may have switched in since the warmer November's 24KWH daily average and its default settings may need some address.

I will speak with Daikin technical.

 

For "Radian" The only info I can supply for heat loss is my SAP calculation states the space heating for my build will consume 14500KW per annum.

 

Thanks Jack for your reply.

 

[ProDave]

2 hours ago, GHDirect said:

The only info I can supply for heat loss is my SAP calculation states the space heating for my build will consume 14500KW per annum.

So 14500kWh of heat is going to need about 4833 kWh of electricity, and at about 33p per kWh at the moment that is going to cost you about £1600 per year.

 

As most of that will be in the winter 6 months, that will average £265 per month in the winter with more of that in the coldest months and less in the shoulder months.

 

How are your actual bills comparing to that prediction so far?

 

Hopefully like mine, the EPC over estimated the heating and my actual bills are lower.

[ReedRichards]

2 hours ago, GHDirect said:

For "Radian" The only info I can supply for heat loss is my SAP calculation states the space heating for my build will consume 14500KW per annum.

 

kW per annum is not a viable unit.  You probably mean kWh per annum.  The other evaluation you should make when installing a heat pump is the rate of energy loss at some specified outside temperature.

 

For example the heat loss calculation made by my installer says I require 8.95 kW of heat to keep my house at 21 C when the outside temperature is -3.7 C.  My worst case electricity usage, earlier this week was 65.84 kWh used in a day, so an average of 2.74 kW when the average outside temperature here was probably around - 3.  In that context 2.74 kW seems remarkably good (the average temperature of my house is probably around 19.5 C as I use a night-time setback).  

[GHDirect]

Hi All.

Sorry typo.

Yes the 14500 should be KWH.

 

Interesting ReedRichards uses night back.

My system stats and their controller offers that by allowing a 2 deg drop over night period (or when the control clock is off).

I tried it but found the system then spent hours trying to get the bungalow back to normal stat settings so have just left everything on 7 x 24 x 365

 

My Daikin Controller was set for "Weather Dependant" and during past 10 days it decided LWT should be 45 Deg.

16th Dec I cancelled WD infavour of "Fixed" and set LWT to 43 Deg.

You can also alter the delta between flow and return which is set to 6 Deg but I left that.

It was still really cold outside 16th & 17th but my KWH per day has dropped to 54 & 37 for each day which is lower than earlier Dec.

Its since got warm outside again so consumption last night was only 30 and today much lower.

Hope this tweak is long term positive.

 

Daikin Controller logs Electricity Consumption by month/year but I did not trust it.

Fitted my own consumption meter November has allowed me to compare the Daiken with my meter and to my surprise they are both tracking almost the same so the Daikin log is accurate.

Therefore using the Daikin history I have used the following.

Electricity Jan - Dec 22 5985 KWH to date

ASHP Heat output for Space Heating 16777 KWH

Its also says 8106 for DHW but this seems high.

From the above can you work average COP?

 

 

 

 

[ReedRichards]

14 minutes ago, GHDirect said:

Interesting ReedRichards uses night back.

 

I have only radiators.  They respond more quickly to changes in the water flow temperature than UFH so are better-suited to night-time setback.

[Marvin]

On 16/12/2022 at 09:16, ReedRichards said:

kW per annum is not a viable unit.  You probably mean kWh per annum. 

@SteamyTeawill be proud of you....

[Marvin]

Hi @GHDirect

 

Is that 300 litre tank in the garage?

Edited December 19, 2022 by Marvin
Spellingggg

[Marvin]

24883 kWh produced. 5985kWh used.

COP of 4.16?

 

SAP suggests 14500 per 52 weeks. 

You indicate 16777 for about 50 weeks,

So about 15% higher?

 

8106kWh for hot water a year is about 22kWh a day. Surely that's too much? Other more knowledgeable people will have to comment.

 

Exactly what insulation was used on the floor and how thick?

 

M

[HughF]

You need to re-enable weather comp really, especially now the cold snap has passed. 43 could easily be too hot for the current climatic conditions.

[gc100]

Out of interest what are you using to measure the power consumption as I’m after something similar?

[GHDirect]

To answer some questions..

The tank is located in insulated area of attic.

The floor of bungalow is concrete block and beam, membrane, 100mm celotex, UFH pipes, 75mm screed throughout.

 

Going to leave on fixed for short time especially as past 2 days its only used 15KWH per day.

 

Energy meter made by Ketotek single phase din rail mounted shows volts, amps,watt and KWH (consumption ongoing).

Purchased via Amazon. Basically it has a "Tail" size hole which you thread your choosen supply cables through.

Mounted mine in my supply cupboard above consumer unit in a small Din rail box threading "ASHP, Immersion and Logic" positives through the hole.

Works great, nice bright and clear display.

 

I think the DHW figure from the Daikin control is questionable. Need to ask Daikin Technical.

Past two days consumption is good immersion probably not even kicked in.

The DWH will have been topped up because apart from daily show my long coated german shepherd sat under it for a 15 minute shampoo & set.

 

 

[GHDirect]

For those interested some follow up information.

December 22 has gone, along with the unusual cold spell.

The following KWH figures show my consumption as against November.

November average outside temp 13 day 6.2 night.  Electricity consumed 634 KWH

December average outside temp 5 day 1.03 night. Electricity consumed 1138 KWH

Thats almost twice the consumption for December where for only 11 days the outside temperature was 0 or as low as -9

How do people In a real cold climate afford to run them or don't they?

[ProDave]

2 hours ago, GHDirect said:

November average outside temp 13 day 6.2 night.  Electricity consumed 634 KWH

December average outside temp 5 day 1.03 night. Electricity consumed 1138 KWH

Thats almost twice the consumption for December where for only 11 days the outside temperature was 0 or as low as -9

How do people In a real cold climate afford to run them or don't they?

Build a really well insulated house.  My annual ASHP heating usage is 1220kWh for the last 12 months.  It is still hovering around 0 here, slightly above in the day, often a lot below at night, was still snowing today.  Normal winter weather up here.

[IanR]

 

3 hours ago, GHDirect said:

How do people In a real cold climate afford to run them or don't they?

 

On 19/12/2022 at 17:19, GHDirect said:

Electricity Jan - Dec 22 5985 KWH to date

ASHP Heat output for Space Heating 16777 KWH

Its also says 8106 for DHW but this seems high.

From the above can you work average COP?

 

Your heating system looks fairly typical for its annual usage.

 

As @Marvin states your COP is 4.16     (( 16777 + 8106 ) / 5985)

 

Although I would look into your DHW usage and/or energy losses within the DHW system, as 8106 kWh appears high. Since this will generally be at a lower COP than for heating, reducing this figure will improve your overall COP, and obviously reduce your energy costs.

 

The step up in space heating energy usage you have seen during the December cold spell, does appear excessive though. I wonder if the 7kW ASHP is only just big enough for your property's energy losses + DHW usage, such that during the cold spell the resistive heater in the ASHP was called upon to support the heating requirements. 

 

Since your SAP calc concluded a 14500kWh annual space heating requirement , but your actual use is 16777 kWh (for 50 weeks), your house is underperforming v. its design level by as much as 20%.

 

Were any corners cut with insulation levels, or window/door performance? Did you get an air test done?

 

For a full 52 weeks your space heating requirement will be around 17,444 kWh. For a 155m² property, that's an energy loss off 112.4 kWh/m² per year.

 

I feel there's some room for improvement, and perhaps some easy gains to be made if you can find what area of the thermal envelope is not perfuming as designed.  Bringing the property at least inline with the SAP calcs, will likely bring the ASHP sizing into line with the property performance and hopefully have it performing better in cold temperatures where resistive heating is required less (if my assumptions are correct).

Edited January 1, 2023 by IanR