Exhaust Heat Pump: Why are my bill's so high?

It’s a lot better than £12 but it’s very difficult to compare to my system. I have 8 radiators in a 1970s bungalow and a different type of heat pump to yours. However the fact that winter months are much more expensive than spring and autumn remains the same, and of course in summer it’s only the hot water that needs heating. 
This graph from my Daikin app shows the kWh used over the last year, for heating and hot water, so the pattern will be similar for you. However I think some of your winter hot water heating might be done by the immersion heater (which is less efficient than the heat pump).

Recently the outside temperature was often below zero degrees C here in Surrey. Whereabouts are you and what outdoor temperatures have you had ?

Are you comfortable with the setting at 18 degrees indoors ? I’d find that a bit brisk !

juliamc wrote:

It’s a lot better than £12 but it’s very difficult to compare to my system. I have 8 radiators in a 1970s bungalow and a different type of heat pump to yours. However the fact that winter months are much more expensive than spring and autumn remains the same, and of course in summer it’s only the hot water that needs heating. 
This graph from my Daikin app shows the kWh used over the last year, for heating and hot water, so the pattern will be similar for you. However I think some of your winter hot water heating might be done by the immersion heater (which is less efficient than the heat pump).

 

So are you just electricity in your place? Or looks like you're using, on average, about 16 kwh per day. Which seems very good, and what I think it should be paying in this modern, A rating efficient flat. 

I'm based near Wokingham. So very close to Surrey. 18c is not the warmest I'll be honest. I'm just afraid to turn it to any further in case the pricing goes mad again. 

In another post I mentioned if the wiring could be faulty in the flat, or something similar. My flat has its own front door with stairs leading up to the flat. At the bottom of the stairs are two switches....one to turn the light on by the door and another for the outside light(which doesn't work). Then at the top of the stairs are two switches...one for the hall and one for the light by the door. However, if you switch that light on, downstairs, then you can't turn it off using the switch upstairs. And vice versa. Surely this can't be right. Could this mean other things are wired incorrectly?

joshantmann wrote:

juliamc wrote:

It’s a lot better than £12 but it’s very difficult to compare to my system. I have 8 radiators in a 1970s bungalow and a different type of heat pump to yours. However the fact that winter months are much more expensive than spring and autumn remains the same, and of course in summer it’s only the hot water that needs heating. 
This graph from my Daikin app shows the kWh used over the last year, for heating and hot water, so the pattern will be similar for you. However I think some of your winter hot water heating might be done by the immersion heater (which is less efficient than the heat pump).

 

So are you just electricity in your place? Or looks like you're using, on average, about 16 kwh per day. Which seems very good, and what I think it should be paying in this modern, A rating efficient flat. 

Apologies. 25 kwh a day. We haven't finished January yet. 

​@joshantmann it's always hard to compare different types of properties, so I'm reluctant to say whether your cost is good or bad. 

Just another thought, what's your hot water schedule set to? How hot is it set to heat to and is it constant reheat or scheduled?

So i believe there is no set heat or schedule due to how the heat pump is setup. I think ​@juliamc looked into this and found something similar

If there is a setting, or schedule, for that I haven't found it

That graph is from the heat pump app so only shows the amount of electricity used for heating and hot water. We do have gas but only for the hob, we also have an EV so our actual electricity use is higher than on the graph. 
Are you able to see how much electricity just your heat pump is using ?  Maybe an individual meter in your consumer unit ? Also giving your usage in £s depends very much on the tariff you’re on. 

Do you know what temperature your hot water is heated to and whether you can adjust it ? 
 

Here’s the heating + hot water usage for the last week. As you can see those cold days used a lot more than the not too bad days we’ve had recently.

I don't think i can see what my heat pump, alone, is putting out. Above is my usage for this month so far. A few wild days which I really don't understand. 

I'm not sure i can adjust the hot water. I need the login details to get into the settings on the pump. I can see it says 'heat request' on one setting. Not sure what that means

Those wild days match my heavy use days (Saturday and Sunday 11th 12th Jan) when the temperature dropped below minus 3. I think you’ll notice an improvement in energy use as the weather warms up.

I can’t see anywhere in the manual (assuming it’s the right one for your model) that mentions the temperature of the hot water. It unlikely that it’s user-adjustable. 

Another thought: can you see your half hourly usage on your OVO account ? That might reveal what’s happening throughout the day.

So this is from Friday. A few things I don’t quite get.

From 2am-4am there is clearly some usage. No idea what that spike is as I was in bed about midnight. There’s also a big spike at 7.30am until 9am. I didn’t get up until about 8.30 that day so, again, I’m not sure what that is. The temperature was set, as you suggested, to 18c for 24 hours.

Any idea what those spikes could be? The total usage for the day was 25 kwh so nothing out of the ordinary.

I think the water heating is a strong candidate. Is there a similar pattern each day ? I’d like to know more about how this system decides when to heat the water as it clearly wasn’t when you’d just used it.

Mine is set to “reheat” which means the hp stops heating the radiators and switches to do the hot water whenever the tank temperature drops below a certain amount, 30 deg in my setup. It almost never does a reheat as I have scheduled heat ups too.

Yours on the other hand keeps the water at a certain temperature all the time and I suspect it’s using the immersion.

The first couple of days I lived in the flat I noticed the bills were incredibly high. Someone, who helps building the flats, told me the immersion was on and that was why things were high. So, since then, I’ve always had that turned off. So not sure it’s that.

Before I switched the temperature to a consistent one throughout the day, I did notice spikes at 7.30am and 6pm (the times I had the temperature to go up). Ironically though, the usage now is the same as then :)

The plot thickens !!

Can you try a comparison for a 24 hour period - switch the immersion back on and see what your half hourly graph shows. If we compare a non immersion period with that (preferably with similar weather conditions which we do have for another day or so) it might give a hint as to what’s going on.

Personally I wouldn’t have the meter checked just yet as I don’t think that’s responsible for these peaks.

I’ve just had someone from the estate agents come over to take a look at things. She is quite new to heat pumps too so didn;t know loads. But I showed her the usage I’ve had the last month, including the nutty £12 day. She did actually mention that the property management team suggested, at the very start, for tenants to have the immersion on all the time. That surely would cost loads?! Anyway, I’ve put it on and let’s see what that does to the price for the rest of today.

It should just be switched on and off by the control unit so won’t actually be drawing power all the time 🤞🏻

So just to clarify, the switch for immersion is on but the heat pump controller will decide whether to actually power it up if it’s needed. 
This is mine:

Switch top right is On but red indicator light is only lit when the heat pump  chooses to use it. Ignore loose cable marked “immersion backup” hanging alongside !!

Evening ​@joshantmann just wondering how you’re getting on with the latest change ie having the immersion switch on? I’m just listening to a podcast about ventilation systems (yes really 🤦‍♀️) and the ducting you have on yours was described as the least good as it falls into kinks and the corrugations tend to trap moisture. It would be far better if it was solid insulated ducting. I think from what you’ve said that you’re renting so I’m not sure what you can do about that, but it does make me wonder what the ducting we can’t see is like.

​@joshantmann not heard from you for a few days but I’m still very interested to know how your system is doing.

Apologies for the very late reply. Still having a few issues with the heatpump and I can’t work out what is going on. The property management team are really not helping me at all and I’m having to do everything myself. I can;t even get into the advanced settings, to try and adjust the hot water, as the property management have no idea what the code is and won’t get an electrician around.

Anyway. Here’s a general example of my usage. This was from the Monday just gone and I actually left my flat for 24 hours at 3pm and turned off my thermostat...you should be able to see that. By the way...I have my thermostat on a schedule in 4 parts, 7.30am-9am (18c), 9am-6pm (15c), 6pm-10pm (18c), 10pm-7.30am (15c). So I can’t work out why there is movement at 4.30am for a couple of hours. In addition there is more movement at 5pm, for 3 hours when the heating isn’t even on!

The immersion hasn’t been on at all and there is nothing else on in the flat. So if anyone has a clue as to what is going on then I’d love to know. Thanks all.

Hi ​@joshantmann When you say the immersion hasn’t been on at all is that because you’ve turned it off somewhere?

My advice is to leave it switched on so it can be controlled by your Joule system.