@vsmith1 It’s interesting that you have a 100 litre hot water tank. I am assuming that you applied for and received the BUS? MCS guidelines required us to have 210 litres of hot water capacity (even though we had managed quite nicely thankyou, on a 99 litre tank before).Because we have (as far as surveys go anyway) a 4 bedroomed house, we had to install the larger tank even though our personal needs don’t require it; they specify the system to the house size not the users personal needs! Regards, Toodles.

@vsmith1 We switched from an EV tariff to cosy tariff after the heat pump installation. We run hot water twice a day during the cheap period, one hour each time to 50 degrees. We have a 200 L tank and it's pretty much around 25 to 35 minutes all the time.

We are averaging about 24 kWh per day during cold winter months and around 15 p per kWh thanks to our battery. So, £3.6 for a warm comfortable house 24*7. Well the open plan kitchen needs a radiator swap as it's just getting to 18 degrees with what they put in. Aira came yesterday to test a few things, we should know soon and hopefully sorted out.

@chandykris And all we need now is fairer pricing for our green energy! We are all doing our bit, but TPTB seem to be dragging their feet don’t they? Regards, Toodles.

February.stats are now in. This was our first full month with an ASHP, so I was really looking forward to the results. To set the context, this February has been a lot colder where we live in the South East when compared to 2024. The total degree days for Feb 2025 has been 290 (for 28 days) when compared to 200 for 29 days in 2024. So, the average temperature in Feb 2025 has been around 5 degrees celsius vs 8.5 degrees in Feb 2024.

For the full month of Feb 2025, we have used 590 kWh of electricity and generated 2270 kWh of heating and hot water. The COP for heating was 4.3 and hot water was 2.9, and chuffed to buts given how cold it has been.The carbon emissions must be only a fifth when compared to Feb 2024 even if the old gas boiler had been running at 80% efficiency.

Glad we went with Aira at a lower flow temperature and upgraded the radiators. By switching to.Ictopus Cosy, we are spending about 15 p per kWh of electricity (thanks to 8 hours off-peak, our solar and battery storage). So, all in all, £90 to keep our home warm during what has been a very cold month. In Feb 2024, we spent about £70 for gas central heating, and that's when it was a lot warmer, different rooms would come on during set periods, and one spare living room and couple of spare bedrooms permanently switched off as they were unoccupied. Even the rooms that were heated would be uncomfortable as you move around the house and couple of WCs were always turned off. Now, radiators in every room of the house are always on.

The added benefit being my study has been warm all the time this February with a new radiator which was previously heated using a small oil filled radiator last year. And the two dehumidifiers are not running as much, given the.house is always warm. So, probably the cost benefit should be even higher but hard to pinpoint how much we exactly used for those dehumidifiers and the little electric heater in my study.

@toodles Yes we did go with the BUS/MCS standards. We are a two-person household, and though technically we are a 3-bedroom house, the box bedroom is a study. Does that explain how we got the 100l hot water tank?

@vsmith1 I have a feeling that some ‘discretionary factors’ may be involved and much depends on the assessor or surveyor; our small room is less than 2 metres square and could hardly be thought of as a bedroom - but them’s the rules that they applied! Yup our bathroom is larger than the room spoken of and that is just 2 metres x 2 metres. Regards, Toodles.

Aira, the Swedish, end to end manufacturer, system designer and installer, with their 15 years warranty, seems to be pushing hard in the UK.

We tested the away mode for the first time as we were away for five days for a holiday. Interestingly, the temperature dropped to about 18 degrees and stayed steady there. For about three days the electricity usage dropped to about 30% of usual, and hot water cycle didn't run. Then the day before we came back, the electricity usage spiked to about 140% of the usual daily range. Maybe, it was also quite cold that morning when it was trying to bring the house back to temperature. Then on the last day, the usage dropped back to about 50%. So, definitely good savings overall, but probably not worth it if you are going only for a weekend. But, five days or more, probably worth setting the away mode as this saved us electricity consumption but still not letting the house drop below a three degrees setback.

I’m an Aira customer with a 6kW Outdoor Unit in a small 100m2 3 bed detached incorporating the new Aira Indoor Unit Compact (about the size of our old combi-boiler) + a separate 200ltr cylinder. We also have 7kW of solar and 32kW of battery storage all leveraging a TOU tariff at 9pkWh between midnight and 7am and an export rate of 12pkWh from 100Green our electricity supplier. AIRA have been superb choice for us based on their long parts and labour warranty and 24/7 call-out which has never failed me thus far. 

One of the other significant factors that determined my ultimate choice was the blend of their external weather compensation, internal load compensation, AI facilitating communication between these 2 elements and the extended Aira Intelligence which provides both monitoring, control and issues resolution remotely. All in all, I find my Aira system a first class end to end (manufacture, design, installation, 24/7 after care), low temperature heating system.

Is anyone else with an Aira heat pump experiencing issues with the hot water or Legionella cycle starting at unexpected times when smart tariff control is enabled? I have noticed both functions activating randomly—often outside scheduled times—so I’ve temporarily disabled smart tariff control to see if that resolves it.

Curious if others are seeing the same behaviour or have found a workaround.

I've not got smart tariff enabled because it always wanted to top up the hot water as soon as you had used any, even at peak times. I only tried it for a few days and gave up on it and went back to scheduling the hot water time and using a setback for a few hours overnight. Are you in the Facebook group, you are not the only one to have random Legionella cycles at the worst times. This isn't effecting me but I'm not sure if that's because I'm not using the smart tariff controls.

Thanks @mikeh. Then I will also go back to non smart tariff control. I just wanted to try this out before the heating season starts, so would have to try in October then.

The Legionella cycle running at random times hasn't been impacted us much as we doubled the storage battery capacity in May. So now have a lot more juice for the heat pump to use and not touch the grid at peak rates.

I am one of the those people who don't use Facebook, Instagram or Twitter, but will ask my Mrs whether she wants to join the group. Looks like some useful information over there.