Air Source Heat Pumps (ASHP) - How have your energy usage and costs changed since getting one installed?

Here is my 2020 and 2021 usage. 2020 i had gas boiler and got my heat pump in Feb was when my installed didn't go to plan and I was provided heaters which as u can see cost me a fortune. I also just got a phev. So my energy consumption has gone up. But not as much as I though. And it seems to be saving so far even with leaving the pump in 20 during the evening and 21 during the day.  You can see the set up took some time as it was not correctly set up. As indicated by the graph 

@M.isterW  I think in my case I should also consider the different approach we are taking now to heating the house in this discussion, as previously with gas on the timer we heated the house for an hour and half in the morning and four hours evening, but now the heating is on 24/7 and as such the house has never been warmer!

All that and at last count I think our heating and hot water bill is up by 20% or so. 

Luckily our Nest thermostat has been logging our house temperature since 2019, unbeknown to me until last Sunday (!) so I have been able to get 15 minute excel CSV readings for the last two years, and going forward I will be producing graphs showing the difference in home heat month by month. I will post a graph at the end of Nov to show the difference this has made. 

So in essence, I’m unsure if we are comparing apples with oranges when matching gas with electric, unless you heat the house in the same way. With 24/7 heating thermal mass of the house and all the furnishings comes into the equation….. And also what cost is acceptable with all that added comfort?  I am happy to pay more if I get more - I suppose the issue is what do you do if you dont want it, and does the defrost cycle then muck things up as that will use electric whether you like it or not. 

15 Oct to 14 Nov 2020 we used about 160kWh of electricity and 2,116kWh of gas (2,281 total)
15 Oct to 14 Nov 2021 we used 577kWh of electricity and 30kWh of gas (607 total)

So, looking at energy usage it looks like it has has fallen by about 73%, which seems like too much to be true. I’m expecting more like 35-45% when I have a proper data set (I estimate heating & hot water is about 70% of our energy usage, including the EV, and with a COP of 2 and good insulation it should fall by a bit more than half). I’m questioning the data but I can’t figure out whether there’s a problem. I can’t do a broader year on year comparison I’m afraid because we only moved into the house at the end of September 2020 (maybe ask me again this time next year). Our habits aren’t much different, e.g. we already had the EV in 2020. We probably do keep the house a bit colder than before and October was quite warm this year. Also, the house is better insulated now than it was and our old gas boiler was very energy inefficient. So, those things help, but I’m still not expecting 70%+ reduction in usage.

Our bills (gas+elec) are about the same as before, in spite of the price of energy being more expensive, and electricity being a lot more expensive than gas. With a COP of about 2, and electricity is about 5x the price of gas, in my head our heating & hot water bill should be about 2.5x more expensive than it was with gas. In the medium term, I expect our bills will be higher than before, maybe about 1.5x higher.

Whilst the kWh combined may have gone down; with gas circa 4p per kWh and electric now circa 20p per kWh the cost, rather than kWh, has defiantly gone up. 

With this trial we are not allowed / able to make use of Time of Use tariffs or technology. I would LOVE to be able to ‘charge’ ALL the Sunamp batteries using cheap off peak electric. BOVO (Before OVO) on Octopus Go, I would charge the Powerwall, charge the car, heat the hot water, turn on the underfloor in 2 rooms all in the 4 hour off peak period. That would run the house for 80%+ of the day

@briannolan  You need to bear in mind that a modern gas boiler is rated at max 90% efficiency, however due to installation issues and lazy installers I read somewhere that efficiency could be as low as 55%. That obviously impacts on a kWh to kWh comparison but not £ to £. 

I’m interested in the replies to this question as I can’t tell. I was on oil before getting the ASHP which meant spending about £750 to put 1,500 litres in the tank. Never sure how long this lasted. I know my elec bills have roughly doubled. 
 

In November last year we were using about 50kWh of energy per day, split into 40kWh gas  and 10kWh electricity. We only used gas for heating and hot water.

At the moment, with a heat pump we're using about 35kWh of electricity per day. The entire heating and hot water system is using about 25kWh with the heat pump using about 20 of that. It isn't typical for the system to use 5kWh per day but we have an unusual hot water setup that uses an immersion heater a lot more.

I'm not sure comparing one month is particularly useful because energy use is weather dependent. We've only had the heat pump for a month so it will be interesting to see how the numbers compare as we go through winter.

As for cost... we're paying a lot more for our energy but our electricity cost per kWh has gone up 50% since last year, which accounts for a big chunk of the increase.

This is developing into a really interesting discussion and note-swapping on the effect an Air-Source Heat Pump is having on all your energy consumptions!

I’m sure that this information could prove really helpful to those who might be considering making an Air Source Heat Pump upgrade in the near future - With that in mind would anyone who’s posted here already ( @M.isterW , @James_N , @48havelock , @briannolan , @jason.lewis , @hambrook ) object to us moving this thread over to our public Smart Home Area to make it accessible to all?  

I don't mind the thread being moved.

I don’t mind at all