Split Air con

[b0rn2sk8]

Surely this is going to depend entirely on how it's powered and what kind of tariff you're on? If the heat pump is 300% efficient while heating at moderate outdoor temperatures, then your electricity unit cost needs to be less than 3x the gas unit cost - I don't see how that's the case on most tariffs these days unless you're on something like Agile and can be selective about when you run it. SVR for gas is around 6.5p, electricity is around 25p, meaning the heat pump will need to be 385% efficient just to match running cost.

You are comparing applies with oranges because you are not factoring in the efficiency of the boiler.

In the sorts of weather we get (like today), the heat pump could be closer to, if not exceeding 400% efficiency, particularly if the poster is using it on low fan speed (low power) to a sensible temperature.

The gas boiler isn’t 100% efficient, it may be rated to 96% but it just isn’t in the real world. It wouldn’t even get up into the 90’s without a full weather compensation set up with flow temperatures well under 50C.

The vast majority of gas boilers are operating in the low 80’s, even modern ones, because they are not configured for efficiency.

If you are heating a single room with a gas boiler it will probably be down in the 50% range because it will be cycling like mad.

 

[Vertigo]

In the sorts of weather we get (like today), the heat pump could be closer to, if not exceeding 400% efficiency, particularly if the poster is using it on low fan speed (low power) to a sensible temperature.

I don't pretend to understand how it all works but the outside unit is rated at up to 4.3kW of heating/cooling power but has a maximum power consumption of 0.98kW which presumably equates to over 400% efficiency at the theoetical max.

 

[b0rn2sk8]

I don't pretend to understand how it all works but the outside unit is rated at up to 4.3kW of heating/cooling power but has a maximum power consumption of 0.98kW which presumably equates to over 400% efficiency at the theoetical max.

Correct but as it gets colder/warmer, the maximum output it can heat/cool will reduce for the same power input. So while that’s the max, when you really need the heating say 5C outside, it will be a bit less efficient than when it’s 12C outside like today.

 

[Vertigo]

Correct but as it gets colder/warmer, the maximum output it can heat/cool will reduce for the same power input. So while that’s the max, when you really need the heating say 5C outside, it will be a bit less efficient than when it’s 12C outside like today.

Yeah, makes sense that it'd have to work a bit harder to suck energy out of the outside air when it's colder. Is there any harm in running it when it gets very cold outside? Tbh on the days when it's like 0C outside, I've refrained from using it, although generally that's cold enough that I want the central heating on anyway, lest the house freezes.

 

[b0rn2sk8]

Yeah, makes sense that it'd have to work a bit harder to suck energy out of the outside air when it's colder. Is there any harm in running it when it gets very cold outside? Tbh on the days when it's like 0C outside, I've refrained from using it, although generally that's cold enough that I want the central heating on anyway, lest the house freezes.

No, its fine, use away at your leisure.