@littlered,

Although the ASHP will be less efficient at night when it's colder, you'll be using most of your electricity on daytime rates simply because daytime rates apply 71% of the time (17/24).  You'd have to check Eon's rates but it's unlikely E7 will be cheaper overall because the daytime rate is always more expensive.  E7 is really for the likes of those with storage heaters, where 80% or so of the electricity is used at night.

@littlered 

As a rough estimate, based on the size of your property and the type of system that you have, you are probably using 2 to 3 times the amount of energy than you should be.

@derek-m Pleased to say after some adjustments we were down to £3.60 today. Phew. Power cut and snow added to the surge in energy use it seems.

@kev-m Well, they kept transferring me from dept to dept and would not tell me the actual day time rate until I signed up for a dual meter, so I gave up on them and came to the same conclusion about economy 7. Thanks for confirming the detail though.

Posted by: @littlered

@derek-m Pleased to say after some adjustments we were down to £3.60 today. Phew. Power cut and snow added to the surge in energy use it seems.

You will probably discover that the reduction in energy use is due to the fact that it is much warmer today.

@derek-m absolutely. I've used 1/4 today of what I used yesterday

@derek-m Yep, weather dependent heating system, something you don't really fully understand or appreciate until you get a freezing cold day.

Posted by: @littlered

@derek-m Yep, weather dependent heating system, something you don't really fully understand or appreciate until you get a freezing cold day.

I think that you will find that all heating system are weather dependent, it is just that ASHP's are more weather dependent than the other types.

@derek-m True 

A neighbour on this new development we had just moved into has told us and other neighbours that he has discovered that our back up system is kicking in all the time which may be what is contributing to our high costs. We are taking this up with the developer. But in the meantime can anyone explain in idiots (me) terms what the back up system is for, how it should be set up and how and if it should be altered if it is coming on? Our neighbour says it is set up to come on at 0 and he thinks it should be at least -5-10?

Posted by: @littlered

A neighbour on this new development we had just moved into has told us and other neighbours that he has discovered that our back up system is kicking in all the time which may be what is contributing to our high costs. We are taking this up with the developer. But in the meantime can anyone explain in idiots (me) terms what the back up system is for, how it should be set up and how and if it should be altered if it is coming on? Our neighbour says it is set up to come on at 0 and he thinks it should be at least -5-10?

Hi LittleRed,

Some, but not all systems, may have a backup heater installed. As the name suggests, it is to backup the ASHP, when the heat pump can no longer supply enough heat energy to meet the heat demand. If your ASHP is correctly sized and installed, it should be capable of meeting the heat demand down to ambient air temperatures of -5C or even lower, so in normal operation the backup heater should only be required 'once a blue moon'. 

If the backup heater is operating frequently, then it would indicate that there are problems with your system that need to be investigated.

@derek-m Thanks to our neighbour who has been monitoring this for a few months, we think that is where the problem lies, as he said exactly what you said in this post. Trying to get the developer to come and change the settings is the issue and currently if we change them we jeopardise the warranty. Will keep you posted, but we are all hopeful that this is the cause of our excess costs.