@editor Can’t have you Trumping your own rules can we?😉 Toodles.

Posted by: @judith

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The coldest day showed full power used in the middle of the night (defrosting clearly on the load figure too) but the day warmed up.

A bit off topic, but just wanted to clarify what 'defrosting clearly on the load figure too' actually means? Cold weather means energy use rises for two reasons, firstly because it is cold, and secondly because COP falls, perhaps by as much as a factor of 2 eg normal milder weather COP of 4 becomes 2 in defrost temperatures, meaning a substantial rise in energy use. A while back I assumed defrosts further aggravated the situation but on the 'Setback Savings - Fact of Fiction' thread there is some considerable evidence that defrosts are probably energy use neutral, give or take. This appears to happen because there is actually an off period for normal heating during the defrost itself, meaning energy (electricity) use falls during the the defrost, but then there is a small post defrost recovery boost which increase energy use a bit, and the two all but cancel each other out. One way of looking at it is that a defrost is a sort of special case mini setback. This means you can't reliably detect a defrost from energy use alone, you either have to look at energy produced (it goes negative during a defrost, heat moves the 'wrong way', from house the the heat pump) or usually more easily by looking at the LWT in relation to the RWT, during a defrost the former drops below the latter.          

Repeating the figure for clarity 

The sampling is only every 5 mins so the accuracy isn’t wonderful. But I would contend that the overshoot (in terms of the integral over time) is greater than the dip of reduced electrical load. To do it accurately I would need to establish the nominal power of each cycle once the boost has finished, which is different on each cycle, and compare the energy above nominal to that below. There’s not much else going on with the house load (except one 7am kettle but I only have the total) so that is another approximation. Overall it looks like about 10-20% more load to me due to de-frosting. Thermodynamically there will be some extra energy since the ice is melted then evaporated or drips off, which doesn’t go into the house heating. 

Posted by: @technogeek

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Now that the world economy is getting a sharp lesson in who really holds world influence, ie Iran (potentially backed by Russia and China), due to the single point of "failure" ie the Strait of Hormuz and the potential major impact on the UK and world economy, do people think this situation will add weight to Ed Milliband's drive to energy independence?

I have a number of neighbours who are dependent on heating oil and at the time of me installing my renewable's equipment thought I was spending a large amount of money unnecessarily. Now those same neighbours are facing a 100% increase in their energy costs and are looking at me with jealous eye's. Will this Iran conflict reinvigorate the UK population to transition to renewable's in the future?

Interesting thought

One can only hope.

We were in that position back when Putin invaded Ukraine, but I fear that as long as bills just continue rising, many a person may not be able to see or understand that prices may have risen more had we chosen to build more new gas fired or nuclear power stations. It worries me that political parties (I'm looking at you, Tories) are quick to set policy (to abandon Net Zero ambitions) to win votes as polling tells them it's easier to sell a narrative that building wind farms is driving up the cost of bills only to spend even more curtailing their output than it is to sell a vision of what the future looks like if we do nothing.

Anyway, I'm happy that my heat pump is currently costing me five times less than oil to heat my house (COP of 4, Cosy tariff 14.8p/kWh, oil at £1.55/L locally). I'm currently draining the last of the oil from my old oil tank for my neighbour in my good deed for the week.

@old_scientist And those of us lucky enough to have our own solar generation will at least have some relief for some months ahead as the heat pump starts thinking about a vacation and the battery has capacity for the rest of the household needs so that immediate hikes in energy prices are less of a concern to us; I realise this may sound like smugness and it is not intended to - just grateful for small mercies. For everyone’s sake, I hope this whole sorry foul-up (toned down expression there) is resolved very soon. Toodles.

Posted by: @editor

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@technogeek, on Ed Miliband's push for energy independence, the answer is a clear yes IMO. This crisis is adding serious weight to it. In his recent statements to Parliament and media interviews, Miliband has repeatedly framed the events as a stark reminder that the UK's long-term security lies in breaking dependence on volatile global fossil fuel markets and accelerating to clean, home-grown power sources we control.

I have been making the same point whenever I hear people raising concerns about fossil fuel prices and arguing for lower taxation.

Also the fact that my virtual equivalent petrol tank is staying still below £9 ... 

I appreciate some people were not able to switch yet but worth highlighting as it is a point not made often enough 

Posted by: @judith

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The sampling is only every 5 mins so the accuracy isn’t wonderful. But I would contend that the overshoot (in terms of the integral over time) is greater than the dip of reduced electrical load. To do it accurately I would need to establish the nominal power of each cycle once the boost has finished, which is different on each cycle, and compare the energy above nominal to that below.

One of the things that has emerged on the setback thread is that even minute sampling may miss some events during a defrost. You need to look at minutes rather than hours on the X axis. Here is a defrost from my heat pump in January this year. The darker blue line is energy in (Wh not kWh!). You can see the defrost dip and then the post defrost recovery. Do they cancel each other out? It all depends on where you put the baseline (what would have happened without the defrost).

I used some AUC estimates (using pixel counting) to get some idea of the energy values from some other charts (see the other thread for examples eg this one and my comment 'I don't have to change the baseline very much to reverse the result, such that the setback and recovery uses more energy than steady state running' - I don't want to hijack this one too much!) and it suggested the energy in deficit during and boost afterwards are not far off cancelling themselves out. The 'nominal power' or baseline, ie what would have happened without the defrost, is extremely difficult to establish, most often because the OAT will not stay steady, and it matters, very small differences in the baseline can reverse say a net energy saving into extra energy used and vice versa. 

@cathoderay I agree the baseline set is tricky and I hadn’t followed the other thread because I couldn’t contribute much.

Off-topic subject closed?

Posted by: @judith

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Off-topic subject closed?

Or just add any further discussion to the other thread. I know it has been somewhat dominated of late by a bun fight between two Mitsubishi heat pump owners over what their respective data, collected in different ways, show, but in a way that is just a reflection on how difficult it is to answer the question of whether setbacks (including the defrost special case) do or don't save energy/money. I'm still collecting my routine data, and come the end of this heating season I will attempt a matched pairs analysis, the matched pairs being days matched on weather, but one with a setback, the other without. This goes at least some way towards solving the baseline problem, at least for whole days, the day without the setback is the baseline. It will be less useful for assessing defrost energy use, because if it is cold enough for defrosts, they will occur, so there are no matched controls without defrosts. But for now, I am sufficiently persuaded on the evidence to date that defrosts do not of themselves increase energy use. It appears to be a classic association is not causation situation, defrosts are associated with high energy use in cold weather, but they are not the cause of or even a contributor to the high energy use. Instead the high energy use happens (a) because it is cold and (b) because COP falls, creating a double whammy to push energy use up.   

I have to admit, the longer this Iranian saga drags on, the more I struggle with it. As I grow older, these situations irk me more and more. My patience for arrogance, ignorance, flexing, bullying, gold-plated White House ballrooms and the casual disregard for the human cost of big decisions is getting noticeably shorter. It genuinely gives me anxiety.

What astounds me most (and I know it shouldn't) is that the decisions and actions of one man can inflict this much damage on billions of people around the world.

What hits me hardest is how heavily this penalises the very people who have been trying to do the right thing. Tens of thousands of us here in the UK have spent our own hard-earned money on solar arrays, heat pumps, batteries and insulation precisely to reduce our reliance on volatile fossil fuels and protect ourselves from exactly these kinds of global shocks. Now those careful, responsible steps are being undermined in real time. Even with renewables on the roof, the knock-on effects (higher wholesale electricity prices, inflated grid charges and the wider cost-of-living squeeze) mean the financial payback stretches out and the sense of security we thought we’d built evaporates. It feels profoundly unfair that those trying to act responsibly are being penalised so heavily by events far beyond their control. I've spent the weekend (again) thinking how we can limit the impact on our household and our finances.

And this stopped being about oil and gas a while ago. It’s now rippling into just about every part of daily life. For the average Brit, we’re already seeing higher food prices because fertiliser costs are climbing, transport and refrigeration are getting more expensive and the entire supply chain is under pressure. Supermarket staples, imported fruit and vegetables, bread, milk, fuel for the car, bus and train fares, building materials for home repairs, insurance premiums... almost everything is starting to feel the strain. Personal finances are being squeezed as inflation eats into savings and wages struggle to keep up. The weekly shop, the monthly energy bill, even something as simple as a meal out… all of it is becoming noticeably more expensive and it's just going to get worse the longer this situation goes on.

Globally it’s even worse. Families in India, Egypt, Indonesia, Philippines, across Africa and many other developing nations are watching cooking fuel, fertiliser, basic transport and the price of a simple meal climb beyond what many can afford. What feels like an annoying extra £200-£400 a year for a UK household can be life-changing for someone on a much lower income elsewhere.

The latest forecasts suggest this won’t clear quickly either. Restarting production, clearing the backlog of rerouted tankers and rebuilding inventories could easily take many months. Looking at previous disruptions like the Red Sea issues, where elevated costs lingered for well over a year, analysts are now talking about the full effects working their way through the system over 12 to 24 months, with some inflationary pressure still being felt well into 2027 and possibly 2028. 

It’s also particularly striking when you look at other examples of strong-arm tactics on energy supplies, the effective US blockade of oil shipments to Cuba, for instance, which has caused severe hardship for ordinary people there through rolling blackouts and economic strain. 

What has also left a sour taste is the recent oil trading activity. Exchange data showed traders placing bets worth around $500-580 million on crude futures just minutes before President Trump posted on Truth Social about postponing strikes on Iranian energy infrastructure. The timing was, shall we say, remarkable. 

Vent session over!

Posted by: @editor

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I have to admit, the longer this Iranian saga drags on, the more I struggle with it. As I grow older, these situations irk me more and more. My patience for arrogance, ignorance, flexing, bullying, gold-plated White House ballrooms and the casual disregard for the human cost of big decisions is getting noticeably shorter. It genuinely gives me anxiety.

I cannot see any way this is now going to end quickly, simply because there is no way out for either side that doesn't involve accepting defeat (and America wont 'win' by sheer might).  My current guess is that it may well last just under 3 years, ie until shortly after the next Presidential elections and even that assumes that the poorer people in America don't choose to shoot themselves in the foot again.  I hope I'm wrong, but Vietnam suggests I may not be.  If you read what the trustworthy commentators are saying its mighty depressing.

@jamespa To my way of thinking, there is one common factor in every war; the decision to declare war is made by a crazed individual and many thousands or even millions of innocent people around the globe have to risk their lives at the whim of such individuals - and as far as I can see, all to no-ones’s advantage in the end. Power corrupts - absolute power …

Regrets, Toodles.