The only things that matters to me - 1. It doesn't cost more to run than the gas boiler we replaced, 2. The house is as warm or warmer.

We've succeeded on both counts. Warmer house, doesn't cost any more.

Nothing else matters... Don't know what my COP is, don't really care.

I absolutely agree! I made huge savings since cheaper tariffs were avaliable at night. I shift just like you. Push it a bit harder when it is cheap. 

This is one of the reason I am so glad we oversized our heatpump a little. I push it hard over a short period. Only need to heate once and the house stays warm throughout. My house is around 21-23c all day. 

Posted by: @andris

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I made huge savings since cheaper tariffs were avaliable at night.

I'm saving even more since switching to a tariff with a cheap rate in the early afternoon, with less of the disruption of the home getting too hot while I'm asleep.

In an ideal world, we still have to look at efficiency as well in order to avoid the "my comfort is paramount and the climate be damned" attitude. However, one needs to be in quite a privileged position to be able to follow a route that is the best environmentally but costs more. As a result, I wouldn't feel comfortable criticising anyone for finding a compromise that responsibly balances cost and efficiency.

But the key word there is balance. The situation @ken-bone has outlined seems to me eminently sensible and reasonable; after all, electricity is cheaper at certain times for a good reason and making use of it during those times instead of peak times has its own altruistic benefits.

Those of us who inhabit the Twilight Zone where a smart meter signal has yet to arrive (along with 2G,3G, and 4G signals) must pursue efficiency and lower costs by a different route. I agree that fixation with COP and SCOP does not help so being imaginative with avoiding the coldest periods for boosting the HP's work load is key, that and a large heat pump!

Posted by: @majordennisbloodnok

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In an ideal world, we still have to look at efficiency as well in order to avoid the "my comfort is paramount and the climate be damned" attitude.

Isn't cost on a time-of-use tariff now partly a representation of how renewable the electricity is at that time? Being more efficient but using more electricity from coal power stations is probably worse for the climate.

Posted by: @mjr

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Posted by: @majordennisbloodnok

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In an ideal world, we still have to look at efficiency as well in order to avoid the "my comfort is paramount and the climate be damned" attitude.

Isn't cost on a time-of-use tariff now partly a representation of how renewable the electricity is at that time? Being more efficient but using more electricity from coal power stations is probably worse for the climate.

Absolutely, hence the "as well as". But you're right; it's not just about efficiency any more than it should be just about cost. Once again, the right balance is the key.

Another point to consider: what happens if time of use tariffs become commonplace, and many more people time their electricity use according to their tariff? What if demand in peak periods falls, and rises in non-peak periods? Given the fact an ASHP will be the major electricity consumer in most settings that have an ASHP, shifting their use to off-peak periods might substantially reduce peak load and increase off peak load, and in so doing remove the basis for time of use tariffs...

Domestic energy use is second only to transport use, and much of that domestic energy use will be used for heating:

Source:

Posted by: @ken

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It's crucial to understand that not all heat pumps can gracefully modulate to the whims of changing seasons. And, frankly, the COP/SCOP is a metric that doesn't translate uniformly across all homes, affected by varying ambient conditions and the specific characteristics of each heat pump.

Sorry, I have to say this post simply serves to muddy the waters. 

I agree that the time of use tariffs may produce savings as a tactic. But in no way can it be seen as a replacement for efficient installation and commissioning. And latterly efficient operation through low and slow heating strategy. TOU tariffs are not a strategy they are a possibly short lived tactic which is a good overlay after the system is set up properly.

lm sure you have good intention but I can see an audience who may wish to exploit this kind of scenario. There is no way I want to see another substitute for proper installation being created by simply telling the customer “just use better tariffs”.

Likewise the manufacturers need to stop piecemeal development of controls with ad-hock   upgrades which aren’t user friendly. 

So I see efficient use of TOU tariffs as a good overlay once efficiency of the overall heating system is achieved. Then you probably will have discovered that’s boost overheating is not efficient or necessary.

but you’re right... CoP is not King.... Efficiency is King.

Completely agree good installation is mandatory.

I think its highly likely that ToU tarrifs will persist, they have, after all, been around for at least the last 50 years!.  They are an obvious way to smooth demand.  This reduces the peak, which in turn reduces the (expensive) network capacity needed and any residual need to burn fossil fuels which, unlike most other ways to generate electricity, can be turned on or off easily.

They may well get more sophisticated and less attractive as night time charging of electric cars begins to become significant thus helping with the day/night balance, but I cant see a way to manage demand without ToU tarifs of some type. 

The maths attached to a cost analysis of this approach sounds daunting. 

It seems to me that there are two variables that would need to be evaluated, i.e,

1 How much cheaper is the night time tariff than day time?

2 What is the difference between Daytime & night time temperatures? Surely it is cheaper to extract heat from warmer air?

I am trying to hedge my bets by mainly heating DHW up at night, but having an additional period at the hottest part of the day. 

Then again, I am in the Algarve, so temperatures and night time tarriffs are different to the UK