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

There’s only one main switch for the immersion. When I first moved in and had the immersion on, the bills were huge. The engineer, who came around, told me to turn it off.

So many mixed messages :)

Trouble is I think the immersion switch still needs to be on. As your system keeps the hot water at a given temperature throughout the day I reckon it’s running the heat pump which gets it to a certain temperature, then might need the immersion to finish the last few degrees. If it can’t use the immersion because it’s not on then it’s going to keep running the heat pump for ages. If you can monitor it for a day, can I get you to switch the immersion on then look periodically at the controller to check how long it’s actually “on” for. One of you earlier photos shows that as “element” I think. 

Can you post another photo of the screen as it is now with the Boiler temperatures and Element status. Thanks.

Quick update. I had someone come around to change the filter on the heat pump and check all the settings. He managed to lower the temperature of the hot water from 55c to 45c. But he did notice there is no way of changing the time you can get the hot water to come on and off. It must be built in to the system.

I had the immersion on, for about 3 days, last week and my bills were definitely higher each day. So I’ve now turned that off. I would say I’m averaging about £5.50 a day at the moment. It’s still just me in the flat, don’t use the dishwasher and the washing machine is used once a week. Heating never goes above 18c. I’ve been having the tv on a fair bit in the evening, but I don’t think that is the reason for the high bills.

​@juliamc is there anything else I should do?

I think now just keep the room temperature at a constant 18 if that’s warm enough for you, or if it’s too warm at night just set it back one degree. Shame about the hot water, however the lower temperature should help a lot. Heating hot water is always more of a job than heating the rooms.