First year of ASHP power use

[Post and beam]

4th October marks the first full year of occupation of our new build. The heat pump has recorded 2650kWh for a cost of £703. This is taken straight from the Vaillant app and yes i know that some believe it to be potentially less than accurate. But ours is a very simple system so i am inclined to go with it unless i discover a reason not to. We have no gas supply so that is all of our heating and hot water.  Happy with this.

Now i need to try to get an accurate idea of what Octopus recorded for everything.

Edited yesterday at 13:27 by Post and beam
Spelling

[JohnMo]

Usage is pretty similar to ours when were doing DHW also.  But not bad for heating and cooling.  Now you have that information maybe worth comparing other tariffs and see how they work out as I assume the £703 is based on a standard tariff and has no solar (battery?) input.

[SteamyTea]

25 minutes ago, Post and beam said:

The heat pump has recorded 2650kWh for a cost of £703

703[£] / 2650 [kWh] = 26.5p/kWh

 

Something does not seem right there.

[Post and beam]

1 hour ago, SteamyTea said:

Something does not seem right there.

Why?

1 hour ago, JohnMo said:

for heating and cooling

Heating & hot water. I cut the cooling fraction out.

[SteamyTea]

1 hour ago, Post and beam said:

Why

It suggests a CoP of 1.

Cost me about half that on E7, storage heaters and an immersion heater.

[marshian]

1 minute ago, SteamyTea said:

It suggests a CoP of 1.

Cost me about half that on E7, storage heaters and an immersion heater.

I think @Post and beam was declaring the electric consumption of the heat pump rather than the heat generated (which would work out as a cop of 1)

 

@Post and beam if you are pulling usage data out of Octopus it can be a bit flakey - I've reverted to the old consumption page because it doesn't have missing data as often as the current consumption data extract

[Post and beam]

OK guys i get what you mean. Apologies.

So, that 2650 kWh is what the Vaillant app records as energy consumed. For a generated 12119. so a SCOP of 4.56

[Post and beam]

As it happens our total electricity use since the board was made live is exactly 6100 kWh as of 2 hours ago. This includes the couple of months prior to us actually moving in full time. so there will be a little consumption not accounted for elsewhere. Small amount, i dont think it changes the figures enough to care.

[SteamyTea]

4 minutes ago, Post and beam said:

SCOP of 4.56

That's better.

[JohnMo]

40 minutes ago, Post and beam said:

generated 12119. so a SCOP of 4.56

CoP sounds good, but heat generated how does that compare to your design energy usage? If 12,000kWh is correct all good. But I thought your house was near Passivhaus standards, so maybe high depending on house size and hot water usage.

[marshian]

42 minutes ago, Post and beam said:

As it happens our total electricity use since the board was made live is exactly 6100 kWh as of 2 hours ago. This includes the couple of months prior to us actually moving in full time. so there will be a little consumption not accounted for elsewhere. Small amount, i dont think it changes the figures enough to care.

 

6100 - ASHP usage of 2650 is 3450 Electric used by other appliances so that's a little over the average but then so are we at around 3600 (2 people in 4 bed house with a reasonable level of tech/convenience)

 

The scop is good too!!! 

 

Edited 23 hours ago by marshian
typo

[ProDave]

If you  are looking for comparisons, My rolling 12 months usage for ASHP  is 1200kWh in heating mode and 700kWh for hot water.

 

That's electrical power into the heat pump.  Measured with a dual rate electricity meter (old dumb E7 electricity meter)

 

No idea of COP my heat pump has nothing to measure output power of even how to estimate it.

[Post and beam]

14 hours ago, JohnMo said:

But I thought your house was near Passivhaus standards, so maybe high depending on house size and hot water usage.

No, i wanted it to be prior to starting but i never planned for it to be. I just wanted to build as good a house as i could arrange. My ACH of 1.4 for example is a slight disappointment as i wanted to get below 1.

House is 201 sq metres by the way.

[JohnMo]

 

9 minutes ago, Post and beam said:

No, i wanted it to be prior to starting but i never planned for it to be. I just wanted to build as good a house as i could arrange. My ACH of 1.4 for example is a slight disappointment as i wanted to get below 1.

House is 201 sq metres by the way.

In that case the overall heat usage may be a little high.  We are similar sized building but a single storey with very poor form factor, loads of glazing and on looking at only the heating and including DHW we are good bit below your quoted heat output (around 2000kWh). Plus your weather is much better than our based on location, so should really be way lower than ours. CoP is great, but maybe how the heat is used could be refined a little. 

 

Are you rooms or areas heated more than needed, is the heat pump cycling more than needed?  Cycle length has big influence on heat developed and CoP.  Depending on cycle length 1 to 2 mins will lead to rubbish CoP and a lot of heat developed, but not much delivered - not sure you here.  But 10 to 15 runs will give a good CoP but the heat developed could be higher than the house needs as some is wasted.  Your Vaillant heat pump has a few tools to help, as you can use a mode that counts deg minutes, this allows long run times and long off times but delivery the correct amount of heat, so if not switched on it may be worthwhile.

[kandgmitchell]

1 hour ago, JohnMo said:

Your Vaillant heat pump has a few tools to help, as you can use a mode that counts deg minutes, this allows long run times and long off times but delivery the correct amount of heat, so if not switched on it may be worthwhile.

This is what I find frustrating about heat pump installations and probably so do many other people considering them - you need a degree in physics to understand their control for the best performance ........

[JohnMo]

3 minutes ago, kandgmitchell said:

This is what I find frustrating about heat pump installations and probably so do many other people considering them - you need a degree in physics to understand their control for the best performance ........

But you maybe you do to get a gas or oil boiler to work its best (neither really need a degree but I get the point).  Trouble with gas and oil historically both have been super cheap, so 80% efficiency install was fine - the running cost difference wouldn't be noticed by the householder.  So S and Y plan became the norm instead of W and X plan (or priority hot water) which allows two different flow temps one for heating the cylinder and the other for the CH.  Setups like that can get circa 95% efficiency instead of 80-85%.  @Post and beam has a pretty efficient system out the box, he could leave exactly as it is, or with a bit of fine tuning maybe save £150, but maybe not.

 

But there are optimisers out there you just strap on and they do the hard work for you, the optimise the energy generation, based on forecast outside temperature, your tariff etc.  Plumber just installs you take the optimiser savings - someone with the degree has already done the hard work. 

[marshian]

24 minutes ago, kandgmitchell said:

This is what I find frustrating about heat pump installations and probably so do many other people considering them - you need a degree in physics to understand their control for the best performance ........

 

You need to have a decent understanding of physics to get the most out of a gas boiler too - trouble is many are just thrown at the walls and sized based on what was hanging on the wall previously and if they heat the house it's all good.......

 

What should be done for any gas boiler replacement is pretty much the same thing that's required for a heat pump - full heat loss assessment - determine the flow temp target - size the rads for the the out put at the design flow temp. Then the installer could be confident of a high efficiency

 

In my case 97 % Efficient when doing CH and 92% Efficient when doing HW

 

Previously under old boiler CH was mid 85% and HW 80%

 

 

[SteamyTea]

Have to be careful when calculating efficiency of combustion.

There are two measures.

 

Higher and Lower Heating Values of Natural Gas

Natural gas has two key measurements for its energy content: the Higher Heating Value (HHV) and the Lower Heating Value (LHV). These values indicate the amount of energy released during combustion.

Higher Heating Value (HHV)

• Typical Range: 42 to 55 MJ/kg
• Definition: HHV measures the total energy released when natural gas is burned, including the latent heat of vaporization of water produced during combustion. This value assumes that all combustion products are cooled back to the original temperature, allowing for the recovery of this latent heat.

Lower Heating Value (LHV)

• Typical Range: Approximately 38 to 50 MJ/kg
• Definition: LHV accounts for the energy lost due to the vaporization of water. It is calculated by not recovering the latent heat of the water vapor produced during combustion, making it a more practical measure for many applications, especially in engines and heating systems.

Comparison of HHV and LHV

Measurement	Value (MJ/kg)	Description
Higher Heating Value (HHV)	42 to 55	Total energy including latent heat of vaporization
Lower Heating Value (LHV)	38 to 50	Energy excluding latent heat of vaporization

Understanding these values is crucial for applications involving natural gas, as they influence efficiency calculations and energy output estimations.

[marshian]

24 minutes ago, SteamyTea said:

Have to be careful when calculating efficiency of combustion.

There are two measures.

 

Higher and Lower Heating Values of Natural Gas

Natural gas has two key measurements for its energy content: the Higher Heating Value (HHV) and the Lower Heating Value (LHV). These values indicate the amount of energy released during combustion.

Higher Heating Value (HHV)

• Typical Range: 42 to 55 MJ/kg
• Definition: HHV measures the total energy released when natural gas is burned, including the latent heat of vaporization of water produced during combustion. This value assumes that all combustion products are cooled back to the original temperature, allowing for the recovery of this latent heat.

Lower Heating Value (LHV)

• Typical Range: Approximately 38 to 50 MJ/kg
• Definition: LHV accounts for the energy lost due to the vaporization of water. It is calculated by not recovering the latent heat of the water vapor produced during combustion, making it a more practical measure for many applications, especially in engines and heating systems.

Comparison of HHV and LHV

Measurement	Value (MJ/kg)	Description
Higher Heating Value (HHV)	42 to 55	Total energy including latent heat of vaporization
Lower Heating Value (LHV)	38 to 50	Energy excluding latent heat of vaporization

Understanding these values is crucial for applications involving natural gas, as they influence efficiency calculations and energy output estimations.

 

I can't remember where I got the calcs for working out the efficiency of my gas boilers but I built a spreadsheet and validated based on the example that gave all the calcs needed

 

I've used it ever since as it's fun experiment and really easy to do (OK I live a sad life)

 

Note OAT temp

Read Gas meter at start (m3)

Collect all condensate over the boiler run period and weigh it

Read Gas meter at the end (m3) and note Flue Gas Temp

 

Spreadsheet works out

 

1. efficiency of condensate recovery as a %

2. Efficiency base of the boiler v Std (Wet Gas Loss of 10%)

 

I think if you are using the same process and calculations you can make an assessment of the improvements to the boiler efficiency

 

In my example I've recently changed my HW Tank to one with a high surface area coil 2.4 m2 v old coil 0.4 m2, This has allowed me to run the boiler at 55 Deg C instead of 65 Deg C when recharging the HW Tank - as a result the boiler is condensing throughout the HW cycle due to return temp being below 54 Deg C

 

Eff Calcs before change said 89%

 

Eff Calcs after change said 92.8% (driven by increased condensate recovery as tank target temp was unchanged)

[Redoctober]

19 hours ago, Post and beam said:

total electricity use since the board was made live is exactly 6100 kWh as of 2 hours ago. 

 

We too are all electric and operating an ASHP - our yearly energy consumption for a 3 bed - 165 sq m house with two occupants [and occasional guests] is running at an average of 5900kwh. Given we are some 300 - 400 miles north of you, I think both figures are pretty good.

Edited 4 hours ago by Redoctober
typo

[kandgmitchell]

1 hour ago, marshian said:

Note OAT temp

Read Gas meter at start (m3)

Collect all condensate over the boiler run period and weigh it

Read Gas meter at the end (m3) and note Flue Gas Temp

 

Spreadsheet works out

 

1. efficiency of condensate recovery as a %

2. Efficiency base of the boiler v Std (Wet Gas Loss of 10%)

 

I think if you are using the same process and calculations you can make an assessment of the improvements to the boiler efficiency

 

In my example I've recently changed my HW Tank to one with a high surface area coil 2.4 m2 v old coil 0.4 m2, This has allowed me to run the boiler at 55 Deg C instead of 65 Deg C when recharging the HW Tank - as a result the boiler is condensing throughout the HW cycle due to return temp being below 54 Deg C

 

Eff Calcs before change said 89%

 

Eff Calcs after change said 92.8% (driven by increased condensate recovery as tank target temp was unchanged)

I think this just makes my point.......................

[JohnMo]

1 minute ago, kandgmitchell said:

I think this just makes my point.......................

But the installer should be the ones doing this not the home owner. Some are switched on to it (but not many) other would look at you like you two heads, even speaking about it.

[kandgmitchell]

Trouble is the installer does presumably do this but then leaves the system set as they feel is appropriate. A short briefing on the the operation, the manuals (mostly installation rather than operation)handed over then off they go. Two years down the line how does one assess whether that set up matches your lifestyle. Finding accessible information that is understandable to tweek the system is hard. Many posters on here have got a very detailed knowledge of the operational side of these units whereas some of us are loathe to fiddle too much; especially just before the heating season........

 

My last full year was 5210Kwh for all in power (no gas) in a 178m2 house with two people and the occasional guests. The next hi-tech addition I'm working on is clearing more plot for a washing line to reduce tumble dryer use! 

[JohnMo]

1 hour ago, kandgmitchell said:

reduce tumble dryer use

Just buy a heat pump version, you won't even notice it being used they use little energy.

[JohnMo]

1 hour ago, kandgmitchell said:

Finding accessible information that is understandable to tweek the system is hard.

1 hour ago, kandgmitchell said:

Two years down the line how does one assess whether that set up matches your lifestyle.

Is it too hot or too cold in the house is the first step? Does it remain so all the time you want it to? If it does maybe not think about it much after that.

 

I like reading technical manuals, do it for fun, but the general UK public doesn't. 5 years ago before building the house I never touched the settings of our boiler, I just forced myself to learn as there was no one to ask.