Mitsubishi Ecodan ASHP - Crippling Bills due to electricity usage.

matelodave

as a start - what flow temperatures do you have set and what is your hot water temperature (I dont know how the  ecodan controller works but it looks like its 48 degrees for hot water an d weather compensation is active. Anything over 50-55 degrees will use the back-up/immersion heater.

others more conversant with Ecodan will have a better idea but a heatpump will seem pretty expensive to run at this time of the year. You should be able to find the EPC on the internet and possibly even the MCS certificate from when it was installed which should give you some idea of the heating requirements and calculations used when the heatpump was installed.

The radiators should have been upgraded when the heatpump was installed so that they could take advantage of lower flow temperatures and therefore improved efficiency and running costs. If the heatpump has just been bunged on as a replacement to a gas or oil boiler then you may end up having to run them at inefficient higher temperatures just to keep warm..

 Do you have a room thermostat. What is it set to, do you have a timer or programmable stat., if so do you have it going off overnight and during the day - most heatpumps work most efficiently with a night set back of 2-3 degrees rather than letting the place get stone cold and then it trying to reheat just for a couple of hours in the mornings and evenings. Do the rads have TRVs

matelodave

Cardew said:

QrizB said:

LozT said:

The house is a 4 bed detached house 2,200 square feet. It was built in the 30s / 40s so I would say badly insulated. We have radiators that look quite old. No underfloor heating.

OK. My 1000 sq.ft. 3-bed semi with partial DG, loft and cavity wall insulation and GCH is using 50kWh/day of heat at present. Your house could well need 100kWh/day of heat but that should need no more than 40kWh/day of electricity.

Depending on how many rooms are heated all the time( to what temperature) and how much domestic hot water is used(again at what temperature) -  I would have thought a badly insulated 1930's detached 4 bed 2,200 square feet house would use far moe than 100kWh a day in Dec/Jan.

100kwh a day for a heatpump implies 250 to 300kwh of heat.

Cardew

matelodave said:

Cardew said:

QrizB said:

LozT said:

The house is a 4 bed detached house 2,200 square feet. It was built in the 30s / 40s so I would say badly insulated. We have radiators that look quite old. No underfloor heating.

OK. My 1000 sq.ft. 3-bed semi with partial DG, loft and cavity wall insulation and GCH is using 50kWh/day of heat at present. Your house could well need 100kWh/day of heat but that should need no more than 40kWh/day of electricity.

Depending on how many rooms are heated all the time( to what temperature) and how much domestic hot water is used(again at what temperature) -  I would have thought a badly insulated 1930's detached 4 bed 2,200 square feet house would use far moe than 100kWh a day in Dec/Jan.

100kwh a day for a heatpump implies 250 to 300kwh of heat.

The OP said he was using 700kWh electricity a week - that includes normal electricity as well as heat pump.

QrizB stated  his house used 50kWh a day using Gas Central Heating and surmised that the OP's house might need 100 kWh of heat which should need around 40kWh electricity. So in line with QrizB's terminology I was suggesting 100kWh was a low estimate for heat needed.

On the EST trials of 70+ retrofit heat pumps many had a system COP of below 2.0(as low as 1.2) so it is quite possible in the OP's house it could also have a COP of 2.0 or lower, especially as it appears he is not operating the heat pump in the optimum manner.

Reed_Richards

I think Laura is probably not a "he", @Cardew.

Cardew is a heatpumposceptic and loves to quote from a trial completed in 2013.  https://www.gov.uk/government/publications/analysis-from-the-first-phase-of-the-energy-saving-trust-s-heat-pump-field-trial#:~:text=The Energy Saving Trust's ( EST,83 households for Phase I. 
I think the results of this trial must have been taken into account when devising the RHI scheme for heat pumps and I believe that to get your heat pump to qualify for the RHI it must have been installed to quite a rigorous standard and should therefore achieve a COP of much better than 2.

However we have not established if this applies to the heat pump that Laura has inherited with her new house.   

addled

If you have a separate thermostat/ timer  this may be overriding the settings on the Ecodan controller.

It's best not to be constantly tinkering with the thermostat and/ or turning the system on and off as you would with a gas boiler. 

I have an Ecodan in a less than ideally insulated house and in cold weather it runs 24/7.  If the house is cooling down a lot between runs and it's having to work hard to catch up then it's unlikely to be efficient. 

Check the hot water is not on constantly, schedule this for when you need it.

Probably not a useful comparison but I am currently using around 25kwh / day (1 bed stone detached).   Also for me an Economy 7 tariff works out best (around 65/35 day/night usage). 

As mentioned you should be seeing larger/ more radiators than normal and they should be warm but not hot.

Suggest contacting the installers asap and perhaps schedule a service so they can walk you through it.  Also download a manual if you don't have one https://library.mitsubishielectric.co.uk/pdf/directory/heating/sales_literature/homeowner_guides

Cardew

Reed_Richards said:

I think Laura is probably not a "he", @Cardew.

Cardew is a heatpumposceptic and loves to quote from a trial completed in 2013.  https://www.gov.uk/government/publications/analysis-from-the-first-phase-of-the-energy-saving-trust-s-heat-pump-field-trial#:~:text=The Energy Saving Trust's ( EST,83 households for Phase I. 
I think the results of this trial must have been taken into account when devising the RHI scheme for heat pumps and I believe that to get your heat pump to qualify for the RHI it must have been installed to quite a rigorous standard and should therefore achieve a COP of much better than 2.

However we have not established if this applies to the heat pump that Laura has inherited with her new house.   

1. Sorry Laura!

2. 'Heatpumpsceptic' is a reasonable description - I think the manufacturers overstate the performance of their Heatpumps and can fool the non-technical when they glibly talk about getting four units of heat output for one unit input.

The link you gave needs reading carefully. I was following both trials carefully and commenting on this forum. The first trial was a disaster and attracted unfavourable comments in the National media. As a result of this unfavourable criticism a second 12 month trial was held and the manufacturers were given carte blanche to select and modify installations - in some cases major changes were made..

Even after these modifications, and given the manufacturers had a huge vested interest to demonstrate improve performance, the average system COP for an ASHP was 2.45. However it is undoubtedly correct that to qualify for RHI an installation should achieve a COP better than 2. If after a year it doesn't your comback is ??? - another gripe.

Given the OP's property is a poorly insulated 1930s house, it might not have qualified for RHI even if it was installed after the introduction of the scheme, and, as said above, with incorrect operating procedures, it is a recipe for high consumption.     

Gerry1

Could there be a less intuitive control panel than that Mitsubishi one?

Does it come with a residential course that explains how to use it?

No wonder people can't get the best from their heat pumps and end up with crippling bills...

shinytop

Gerry1 said:

Could there be a less intuitive control panel than that Mitsubishi one?

Does it come with a residential course that explains how to use it?

No wonder people can't get the best from their heat pumps and end up with crippling bills...

To be fair it's not too bad considering it almost avoids using any words at all and relies mostly on symbols.  There are some quite good YouTube videos on how to use it 

lohr500

Hi Laura,
Just a thought. Are you receiving any Govt. RHI scheme payments for your heat pump system?
If the previous owners obtained the RHI grant to subsidise the installation and it was less than 7 years ago, then my understanding is that the grant repayment should transfer to you as the new house occupier. 
 

matelodave

Gerry1 said:

Could there be a less intuitive control panel than that Mitsubishi one?

Does it come with a residential course that explains how to use it?

No wonder people can't get the best from their heat pumps and end up with crippling bills...

yes, there is.  Try the one on my eleven year old Daikin and some programmable thermostats require a Masters in programming skills if dont want to use the default settings.

The Ecodan looks quite easy in comparison and TBH if the system has been set up and commissioned properly then it shouldn't really need much tweaking or adjustment. Once I'd got mine set up to my satisfaction then it just gets on with it and I'm sure that some of the others like R_R and Shinytop will be the same when they've sorted theirs out.

Although that said, I do understand that for the vast majority of people they just want it to work like the old boiler that they are used to rather than others who like to tinker to optimise their systems.

However, are still more expensive to run than mains gas and always will be whilst leccy is four to five time the price of gas. Going green isn't going to be cheap.

This is speculation on my part but from what Laura has said, it may be that someone has just shoved a heatpump onto the front of an old gas system which was one of the cause of a lot of dissatisfaction in the early days. She really need to get hold of the paperwork (MCS Cert and any other calculations to see what was actually done and when). As the owner she may even be entitled to claim some of the RHI if the unit was MCS installed within the last seven years.