Also this is based on a standard electric tariff. We're on Octopus Go, so 5 hours of our usage is at 8p rather than 30p. Our 'real world' average unit rate is therefore 23p/kWH meaning the above prices come down a bit too.

I do the same maths weekly when trying to tell people how the maths adds up….

My gas boiler is 72% efficient so my break even cop is something ludicrously low like 2.34…

Tl;dr - I don’t have my ashp installed yet due to building delays.

I don't fault your maths for your use case, but a lot of people complaining don't know how to use their heat pumps properly. You can't go all that wrong with a boiler really, maybe dropping 10% efficiency from too high flow temps, but doing that with a heat pump can literally double your bill, and that's when the questions start. 

@benseb, quick question. Are your numbers based on the boilers and ASHP running 24/7?

@editor they are based on the heat outputs shown. So the cost of gas and electric to produce 2498kWh of energy. Which shouldn’t really matter much with gas and oil how long they are on for. 

with ASHP mine is on 24/7 but with setback of 2c overnight. 

I’ve actually just tweaked this as we’re on cheaper electric 9:30-2:30 so I now turn down the heating 6:30-9:30 then let it play catch-up in the cheap period. It’s not normally noticeable especially with a warm kitchen from cooking but it’s a bit more noticeable when -5c outside this week!

Yeah I've worked out the same for me - producing the same amount of heat that our ASHP is producing using our 20-year old gas boiler would be 40-50% more expensive, even in this awful December we're having. A modern condensing gas boiler might be cheaper right now, but not significantly so, and certainly not enough to outweigh the benefits during warmer weeks/months.

One thing this energy crisis has done is made the payback time on all these green investments a complete non-issue. I didn't really care about payback time before, I just did it because this stuff is better technology, but this winter has brought the payback forward by a good few years.

Posted by: @benseb

↑

with ASHP mine is on 24/7 but with setback of 2c overnight. 

I’ve actually just tweaked this as we’re on cheaper electric 9:30-2:30 so I now turn down the heating 6:30-9:30 then let it play catch-up in the cheap period. It’s not normally noticeable especially with a warm kitchen from cooking but it’s a bit more noticeable when -5c outside this week!

I'm trying to work out the best way to run my ASHP with Economy 7. Our cheap tariff runs from 11.30pm to 6.30am. At the moment I have the thermostat set to full temperature from 4am to 7am so it's warm in the morning, and have it a degree lower during the day, then higher in the evening and setback by a couple of degrees from 10pm. The DHW is also set to heat up at 2am. I wonder though whether it would be better to have the heating on full temperature throughout the cheap period? It's underfloor heating in screed so I fell like it might be better to store more heat in the slab when the electricity is cheaper.

Posted by: @bob77

↑

I'm trying to work out the best way to run my ASHP with Economy 7. Our cheap tariff runs from 11.30pm to 6.30am. At the moment I have the thermostat set to full temperature from 4am to 7am so it's warm in the morning, and have it a degree lower during the day, then higher in the evening and setback by a couple of degrees from 10pm. The DHW is also set to heat up at 2am. I wonder though whether it would be better to have the heating on full temperature throughout the cheap period? It's underfloor heating in screed so I fell like it might be better to store more heat in the slab when the electricity is cheaper.

 

Similar here. My tactic is to have the heating come on early enough to hit target at 7am, which of course varies with how cold the house gets overnight, but is usually some time between 0300 and 0600, with DHW heating at 5am ready for morning washes. You will probably want yours to come on earlier because underfloor heating has more inertia (but doesn't require as high temperatures), but there doesn't seem much point putting it on full the whole time and heating the room while no-one's there because everyone is asleep.

I'm also slightly worried by the mention of "thermostat" instead of weather compensation, but that might just be language.

Posted by: @mjr

↑

I'm also slightly worried by the mention of "thermostat" instead of weather compensation, but that might just be language.

The room thermostat controls when the UFH calls for heat, and the weather compensation controls the flow temperature that the heat pump delivers. Is that wrong?

The room thermostat is at 19.5C during the day, 20.5C in mornings and evenings, and 18C overnight (until the cheap-rate heat-up period which is set at 20.5). M