[djhworld]

I'm on a electricity tariff where the per kWh unit price changes every 30 minutes, you're basically being charged at market rate or thereabouts, the prices for the next 28 hours are announced at 4pm every day.

Generally the prices betwen 4pm-7pm are expensive and the rest of the time it's cheaper - although with current world events things have gotten a little spicy lately.

On really windy days you definitely get to see the benefit where prices drop to zero or even negative, which is great if you have an EV or something to dump lots of power into. Looking at todays prices they're like 1-3p p/kWh!

But that doesn't last, as the wind dies things start to get back to normal.

The key with the tariff though is to just play the averages and generally avoid high power usage during the peak periods. My average for the last 2 years was around 30% cheaper (p/year) than what I would have paid if I was on a normal energy tariff.

It will be interesting to see whether that trend continues, especially with the state the world has suddenly been thrown into.

[bjackman]

I wonder if we'll start to see gimmicks in home appliances for taking advantage of variable prices.

Like for EV charging I assume it's a basic requirement, you simply wouldn't buy a car that didn't let you adjust the charging schedule based on cost.

But what about... Freezers? Maybe there are scenarios where your freezer could drop 20° below its usual temp while prices are low, and thereby avoid running the compressor for several hours while prices are high.

What about a tumble dryer button that says "these clothes are fine to stay wet for up to 8 hours, dry them at the cheapest moment during that window"?

TBH I doubt these things would really pay for themselves but as a consumer I'd still be tempted by the "lol, neat" factor.

Also I assume the local-LLM heads are already finding ways to have their agents do useful work while the GPU can churn tokens for almost-free.

Also makes me think of fun Home Assistant workflows. Like, "when energy is expensive, just try to keep the house between 16-26°. When energy approaches free, I want to live at exactly 20°". (I assume heat pumps also have ways to take advantage of this in more roundabout ways).

[djhworld]

I think freezers would definitely be a gimmick as they don't really use that much power.

I can see it being a nice feature for higher-load tasks though, e.g. my dishwasher uses about 1.8kWh for a cycle. On this tariff it's trivial to compute the best start-end time based on the 30 minute price windows, so if the dishwasher could do that it would be pretty sweet. Right now my dishwasher just supports a 3h delay function. I wouldn't mind if my dishwasher had a (local) API you could hit to control its schedule. Sadly this usually comes with some cloud requirement though.

[3form]

I think freezer could be comparable, no? How many cycles of dishwasher are you running per day?

[kalleboo]

Our Mitsubishi heat pump water heater has integration with some solar systems and weather services to attempt to time hot water production to solar peak.

We don't have solar panels but have a solar energy plan (cheap during the day, expensive during dawn/sundown, average overnight with fixed hourly schedule independent of actual production) so for us it's just programmed to follow a fixed schedule of prioritizing filling up during the solar hours and 100% forbidden from filling up during the expensive "duck curve" hours.

[upofadown]

Things like freezers don't take a huge amount of power. It's definitely about things that do space heating/cooling. The traditional approach is to put your electric water heater on a timer. That way you can schedule your hot water use on a consistent schedule but only heat the water at night when you can be sure the rates are lower.

[pseudohadamard]

In my case I've got a contactor on the house power board that disconnects the hot water at night, so it's only heating off solar power. You can also get specialised solar diverters that do the same thing, but they cost literally ten times as much and only squeeze a tiny bit of extra efficiency out of the system.

If you do go down this path, make sure you insulate the crap out of the cylinder and surrounding water pipes, mine only heats once a day and that's once the sun's providing the power for it.

[fracarma]

I second this. I live in Spain and put solar panels on my roof. I have no batteries. In the last 2 years, the price of the energy returned to the grid has been 0 or even negative. Therefore I started running automation using Homeassistant and I'm stuck at appliances that cannot be simply turned on and off with a power switch (i.e. my freezer, the AC, washing machine etc). If someone could produce a refrigerator that I can control via an open protocol(i.e. ZigBee) it would be awesome!

[cogman10]

You can basically do that today if you wanted to by buying consumer grade batteries and smart switches. A whole house battery would be better, but it's more expensive to install.

For the tumble drier and dishwasher, those usually come with time delay features. That's usually good enough if your goal is to timeshift a load.

I have a battery for my fridge not for this purpose, but because I'd rather not have a power outage spoil my food.

[philjohn]

With "smart" appliances that can be controlled, there's often a community integration to HomeAssistant ... and then there's the free EMHASS addon which will optimise for profit, or self consumption based on energy prices (both incoming and outgoing) as well as any on-site generation (e.g. Solar PV) batteries etc. etc.

Neat piece of open source software.

[muskstinks]

I'm following battery prices and you can now get 25kwh for 3.5k. This will be a solved problem a lot sooner for a lot of people.

A heat pump house uses perhaps 40-50kwh in deep winter.

[rimunroe]

> A heat pump house uses perhaps 40-50kwh in deep winter.

Over what time period, and where? My geothermal system draws about 1200 watts when heating our large house on the coldest days of the year

[muskstinks]

Argh... i wanted to write 1-2 days.

I meant it as a short buffer

[rimunroe]

Ah gotcha. That seems much more reasonable!

[theowaway]

Just buy a home battery. Sheesh, there were solutions to problems before LLMs

[kortilla]

Yeah, but that’s strictly worse for some of these examples. You can’t overcome the loss of energy just going into the battery and getting it back and the there is the huge cost of the battery itself.

The freezer example would require like $10 of electronics assuming there isn’t already a WiFi chip in it.

[Gareth321]

Yeah this is the simplest solution. I'm hoping my next EV can do V2H and act as a home battery.

[fastasucan]

Many homes in Norway has this. Its a smart plug in your fuse box. For me it offsets EV charging untill the electricity is at its cheapest, it also cuts down on heating for the peak hours etc etc.

[newsclues]

There are devices to store hot water.

[declan_roberts]

That's a great system. Like so many things, success comes down to implementation.

In California, for example, PG&E will charge you the maximum peak demand prices while simultaneously paying other states to take electricity during the solar duck curve.

https://www.eia.gov/todayinenergy/detail.php?id=56880

[bullfightonmars]

Are you saying that they don’t let rate payers take advantage of low rates to advantage load shift?

That seems counterproductive and exploitative.

[gcheong]

I have an EV and am on a Time of Use rate plane here in SF. My lowest rates are between 12am and 3pm every day. I charge the car and run everything I can in terms of major appliance use between these hours (dishwasher scheduled to start at midnight or manually run early in the day, washer/dryer loads run in the morning). I am home during the day which makes this easier to do though. Another solution of course would be to bank your solar generation or low rate electricity into a set of batteries that you could draw from during peak times.

[amluto]

PG&E doesn’t even give all its time-of-use ratepayers the same peak hours. The rates are nonsensical.

[pseudohadamard]

Australia has that in an even more extreme form, although it's more an emu curve there. In fact the CA one isn't really a duck any more either is it?

[dabeeeenster]

I'm on a similar tariff in the UK and just had a 10kwh battery installed which is just amazing for shaving off all the load between 4-7pm. Whole system installed was ~6k GBP and I think my payback time is going to be < 5 years which I'm super pleased with.

[sjducb]

Would you mind sharing the tariff name and company?

[thebruce87m]

I would also like to know the company name please.

Would love to get a Forster battery + invertor system installed. Seems like the battery is £2k for 16kWh and maybe £1k for an inverter? so interested in your cost breakdown.

https://www.fogstar.co.uk/collections/solar-battery-storage

[belorn]

How are the fixed costs in this? Here in Sweden I have seen a strong trend that as the grid has become more variable and connected to the European grid, a larger portion of the bill becomes fixed. For most part of the year, the fixed costs are now greater than costs that scale with consumption.

Transmission and construction, crewing and maintenance of of thermal power plants (under the name of "reserve energy") cost a lot of money, which in turn becomes fixed grid costs. On top of that you got consumption costs during periods of poor weather, which in combination of high fossil fuel costs means that the consumption prices spikes. The cost of energy during optimal weather conditions is in contrast so low that at this point they can basically just be rounded down to zero.

[Worksheet]

Chris Norbury, CEO of E.ON UK said:

"Some of the modelling we have suggests that you could get to a position by 2030 where if the wholesale price was zero, bills would still be the same as where they are today because of the increase in non-commodity costs."

Fixed costs are enormous and are increasingly driven by paying for the CFDs that back up the economics of wind. The CFD scheme allows wind producers to de-risk from market prices by locking in a fixed price with the government who then recover this from bills.

So, yes you get to enjoy low variable costs when it's windy, but you pay for the priviledge year round.

I do think that wind has a part to play in the UKs long term energy mix, but by this point I'm happy to call the current scale-up a complete false economy.

Household and industrial electricity bills are double what they were in real terms 15 years ago.

[youngtaff]

> I do think that wind has a part to play in the UKs long term energy mix, but by this point I'm happy to call the current scale-up a complete false economy. Household and industrial electricity bills are double what they were in real terms 15 years ago.

The CfDs set a floor price when there’s lots electricity being generated by renewables but they also contribute to bills when the market price is over the strike price

Electricity bills are higher because we’ve had two fossils fuel shocks in the last 5 years and the costs for decarbonisation are added to electricity bills rather than gas ones

[gendal]

The amount wind farms in the UK have contributed back over the last ten years is a rounding error compared to how much they have received. It's not even close: https://x.com/7Kiwi/status/2031657347433603581

And the scary thing: the wind farms aren't even making that much money! Some projects have been cancelled and others had to re-bid in subsequent auctions to get a higher CFD price than they originally received because they couldn't make the economics work. Worse, there are reasons to believe they're not even fully provisioning for their end-of-life decommissioning costs.

The UK's energy policy is unbelievably destructive :(

[youngtaff]

Where’s his methodology?

How does he separate the CfD price from the market price that’s being set by renewables?

Where’s his evidence that using gas would be cheaper than renewables?

[gendal]

He explains on his website where he gets his data from. He gets it from The Low Carbon Contracts Company... y'know: the firm who is the actual counterparty to the CFDs and so should probably know the actual sums of cash being moved - and in which direction.

His January article: https://davidturver.substack.com/p/record-january-cfd-subsid...

LCCC's relevant data page: https://dp.lowcarboncontracts.uk/dataset/actual-cfd-generati...

The actual spreadsheet: https://dp.lowcarboncontracts.uk/dataset/8e8ca0d5-c774-4dc8-...

And note: even when gas is more expensive than the CFDs, the huge fixed and/or policy costs (network build-out, capacity market, curtailment, etc) are devastating.

The story would be completely different if wind farms were actually cheap to build and run... the problem is they're just not.

I wish it were not so... it would be great if we had a path to being free of dependence on hydrocarbons. But in a battle between wishful thinking and physical and economic reality, reality usually wins.

So we're faced with a choice as a nation: continue to pour tens of billions of pounds down this drain... or call time on the experiment and free up all that money for something productive?

[terabytest]

Why did you choose this plan in place of a fixed price plan?

[djhworld]

Explained above, I WFH, single (no kids) and have an EV - but I don't use the car for commute etc so I can be choosy about when I charge the car and take advantage of the ultra cheap periods.

Fixed price advantage is you use power whenever you want. Your average unit rate is just the price on the tariff. Predictable and safe.

Agile price changes every 30 minutes, so you need to do a little planning. But if you take advantage of the cheap periods you'll generally come out on top. My average unit rate last year was like 16.5p p/kWh whereas the standard tariff was 23-24p, so some nice savings. There's also some risk involved - the price can go up to £1 p/kWh and a few days in winter in 2024 it did that for a short while (around the peak periods) so you have to take on that risk - and obviously being exposed to the world energy markets does mean you get exposure to stuff like wars impacting global markets.

I mean there's nothing stopping you from using lots of power between 4pm-7pm it's just you'll drag that average unit rate up to the point where it's probably not worth it. When I say "use lots of power" I don't mean like I sit in the dark between 4-7pm, it's just I avoid the big ticket power users like ovens, showers, cookers etc

[roryirvine]

Yeah, and the really important point is that you get to see the prices a day ahead, which is what makes it actually pretty easy to live with.

For instance, if I know it's going to be expensive when I'd be cooking tomorrow's evening meal, then I won't make something that would need a long time in the oven. And if it's going to be particularly cheap around lunchtime, then I'll plan to do a big load of laundry then.

I have electric heating, which I thought might be a cause of anxiety but it's not really worked out that way. The temperature in my flat won't go down by more than a degree or two with the heating off over the course of the sort of 4 hour price spikes you tend to see in mid-January. If it looks like it's going to be unusually bad, I could always raise the temp by half a degree beforehand, but in reality I've only bothered to do that maybe three times in the past couple of years.

Basically, it's just another thing to factor in when planning my day. No more of a hassle than checking the weather forecast or glancing at my calendar.

[phil21]

> Basically, it's just another thing to factor in when planning my day. No more of a hassle than checking the weather forecast or glancing at my calendar.

Sounds like an incredible hassle at a level I would pay hundreds of dollars per month to avoid. That sort of mental overhead is crazy to me. But I'm also someone who finds having a single event on my calendar for the day disrupts my productivity and mental peace to an absurd level.

Time of day billing is definitely the future for renewables though, once they hit a saturation point for the grid it's the only thing that makes any sort of sense. Perhaps residential is the last place it needs to happen, but eventually it will be the norm. I see it working more in an automated fashion though. Smart load centers (panels), smart appliances, etc. that are connected to the local power company's API. Then you set some rules around it.

Stuff like cooking dinner though? I cannot imagine planning my day around saving a couple bucks. That's just insane to me. Energy use and all this mechanization/automation/technology exists to make life more convenient in the first place! Stuff like EV charging, raising/lowering temps in anticipation of power pricing, laundry (dryer) scheduling, etc. seems to be where 80% of the wins can be made, and are all much more automatable to avoid having to think about it. That last 20% can simply be taken up by whole-home battery storage, which by the time any of this happens at scale will be pretty much the norm.

The thing that concerns me most though are regional "seasonal" events where a once-a-decade lul in energy production happens and there is simply not enough dispatchable power on the grid to meet demand due to everyone hyper-optimizing their loads in such a fashion.

[djhworld]

> That sort of mental overhead is crazy to me.

I've been on the tariff for 2 years now, at first I was looking at the prices every day, but over time you get used to how it works and the price watching starts to tail off. The rule of thumb is just to avoid high load stuff during the peak window (load shift) - sticking to those principles you generally come out of on top. Playing the averages is the key.

Nowadays I don't really look at the prices that much other than when it's windy as I might be tempted to charge the car.

That being said though, if current world events continue and the energy situation degrades further - causing my average unit rate to start creeping up, I might consider getting a home battery , solar etc to compensate, or leave the tariff entirely.

[roryirvine]

Yeah, it's definitely a bit of a game for me, and my electricity bill was already low enough that the savings are trivial.

But I'm the sort of person who enjoys being flexible when planning my day. I'll fit chores such as laundry around work meetings. Decide whether to go for a lunchtime run (and thus have an extra shower) based on the weather and having an a big enough gap in my day. Buy ingredients for dinner based on the weather and how I'm feeling. Expected energy cost is just another factor in the mix - and one that only rarely becomes decisive.

The closest the UK grid has ever come to not being able to cover demand was a few years ago when most of our nuclear fleet went offline at the same time in the middle of a January cold snap due to the discovery of a potential maintenance problem in the steam plant. If there were to be a repeat of that scenario, then the spread of domestic dynamic pricing would actually help matters by driving load shifting behaviour.

[rsynnott]

Some people enjoy this sort of hyper optimisation, even if they don't really need to do it.

[account42]

> For instance, if I know it's going to be expensive when I'd be cooking tomorrow's evening meal, then I won't make something that would need a long time in the oven. And if it's going to be particularly cheap around lunchtime, then I'll plan to do a big load of laundry then.

That sounds like something out of a dystopian novel lol.

Imagine setting up a complex system like this where you have to plan your food choices around energy prices when people in other countries pay a fraction of what you do all day around.

[bethekidyouwant]

Bananas. I hope you do this because it appeals to you at some level.

[irishcoffee]

A decade back, in the US, the local power company would give you a discount if you used less energy than average during peak hours. At the time I had a vacant rental, very little energy use. (FWIW I’ve since sold it, being a landlord isn’t a good time)

I watched a specific neighbor go through great pains to honor this system and so as to reap the benefits of a much lower bill. Sweating their buns off during the hottest part of the day, open windows, no tv on, etc. fully committed.

They saved 8 dollars that month. My vacant rental, not doing a goddamn thing, saved 6 dollars.

If your system is similar, you’re optimizing your life around the cost of a monthly Netflix subscription, at best.

[djhworld]

There is an element of truth in that if you go to the extremes, where it's almost definitely not worth it.

I don't sit in the dark during the peak times, during the week I'm working during that time anyway and I still have my monitors etc on. It's just I don't usage high-draw appliances like cookers during that time. I eat dinner after 7pm anyway.

Also I have an EV, but don't commute or travel long distances regularly, so I charge my car when opportunity strikes, especially when the prices go negative - this means I don't really spend that much on fuel really. The savings really start to come in if you have "bursty" high energy stuff that can take advantage of the cheapest periods like an EV or home battery. If you just have "baseload" stuff that runs all day like A/C or whatever then yeah you won't really see any significant savings.

[irishcoffee]

I contend you’re still saving the cost of a lunch meal… per month.

[01HNNWZ0MV43FF]

Not GP but I assume the fixed prices have to be fairly high to account for people using lots of power during peak demand when most people use lots of power?

[djhworld]

Exactly.

For me I'm happy to avoid big power draws during the peak times, as I'm 'compensated' for it outside of those periods with a little planning. Downside is when the wind is not blowing AND disruptions to global energy markets - I'm exposed to that, warts and all, there's definitely been an increase in prices over the past 4 weeks, although there has been a few days (including today) where the wind has basically made the energy free and my average unit rate is dropping again.

[Kaliboy]

It's not only that, you also need reserve for the intermittent sources like wind and solar.

I live on an island, we have big batteries that can supply up to 15 MW of power for a period. In the Netherlands we have natural gas plants that are called up when the wind or sun output decreases, lest the grid frequency drop.

[rwmj]

My friend has a car which can charge only when prices are low. I'm not totally sure how it works though, does the smart meter communicate this to the car?

[djhworld]

Some chargers communicate directly with the energy supplier and charge at the cheaper rates.

You can do this yourself as well with home assistant (if your charger supports it) and some API calls. It's just a matter of telling the charger when to start and stop the charge. The rest of the communication between the charger and the car is some protocol I can't remember the name of.

[acron0]

Could be wrong but I guess it more likely communicates with the charger. The car will always try to draw if it's plugged in, but most chargers can be switched on ("charge") and off ("don't charge") remotely. It's probably quite trivial to have something watch the price of power and on/off as appropriate

[pornel]

Energy providers use whatever internet API there is for either chargers or cars.

Octopus UK has a list of charger models and car brands they support for their special tariff for cheap off-peak EV charging.

The charging cable has a protocol for negotiating power, so either side can pause and restart charging.

[reillyse]

My car hits the api for my power company and knows how much charge it needs and plans out its charging schedule, always avoids peak.

[fastasucan]

No the smart meter communicate with the charger.

[thebruce87m]

Or the car. Octopus in the UK can control both cars and chargers depending on compatibility. They control my Tesla as my charger isn’t compatible.

[djhworld]

....that being said, when you see stuff like this page and news articles about cheap renewable power etc, there are A LOT of negative reactions to it (even evidenced by the comments on here!) because for most people in the UK they never really see any direct benefit - energy prices seem to keep going up and a lot of people are on contracts with fixed rates that rise often.

I'm not sure what the solution is, I know that the price of electricty is dictated by gas so maybe decoupling that will help - but that probably has complications with balancing the grid.

The tariff I'm on (Octopus Agile) suits me as I WFH, have an EV and it's just me living in the house, I can move my usage outside of hte peak periods quite easily and I built a website to help me find the cheapest charging periods for my car based on the prices for the next day. The other day my average unit rate was like 2p per/kWh and I dumped like 30kWh into my car lol

[gendal]

Yes - the wholesale price of electricity can sometimes be very low (or negative), particularly when there is a lot of wind. And some tariffs pass that on to consumers. But I don't see how it works at scale.

This is because the wind farms don't get paid the wholesale price. They get paid their guaranteed, index-linked CFD strike price. This means that, for every £1/MWh drop in the wholesale price, they get an exactly matching extra £1/MWh to top them back up to their strike price. They can bid a low price into the market safe in the knowledge they'll get paid their CFD price.

And that top-up has to be paid by somebody: either other bill payers, or the taxpayer.

That wouldn't be so bad if the strike prices were low. But they're not. The recent "Allocation Rounds" guaranteed offshore wind farms in excess of GBP100/MWh, index linked for at least 15 years.

To put it in context, these numbers are higher than the wholesale gas price - even with an uplift for carbon externalities - for all but the worst period of the Ukraine invasion a few years back.

But it gets worse: on top of these extremely high fixed prices for wind, we also have to pay for the installation of tens of billions of pounds (if not more) of new grid connections, because the wind farms are nowhere near the centres of demand. This cost is also added to bills.

It doesn't end there. Readers may be aware that the wind doesn't always blow. Which means we need something that's able to spin up or down on demand. In the UK, that means gas. So we have the ridiculous situation of having to pay the gas plants to sit around doing nothing, just so we can call on them at minimal notice when needed. And remember: there can be long periods with basically zero wind or solar (the famous 'dunkelflaute' phenomenon in winter).

This means we need non-wind capacity pretty much equal to peak winter demand, in order to be safe during the week or so some years when there's no wind.

So we're paying to build and maintain TWO generation systems in parallel.

This is why electricity costs in the UK are on an ever-upwards trajectory: all these 'policy costs' are added to the wholesale price, and are a large and growing component of the _retail_ price that most consumers pay.

Depressingly, 'storage' doesn't fix this. Indeed, it's a fun exercise to calculate how much electrical energy is consumed in the peak of winter in the UK over a one- or two-week period and then figure out how much the necessary battery capacity would cost... or, even more fun, how many Welsh and Scottish valleys we'd need to flood to create the pumped-storage capacity. We're talking tens of trillions of pounds.

I fear the UK has, with the best of intentions, made a mistake of generation-defining proportions with its bet on wind :(

[demosito666]

In other words, betting on wind (or sun) where there is little wind (and sun) is not an optimal choice. But folks on HN were telling otherwise. Who might’ve known…

[youngtaff]

If it’s all due to the reliance on wind and the floor price CfDs set why does the price spike when oil and gas prices rise?

[gendal]

It's a good question. To be honest, I'm still trying to get my head around how the UK electricity market works. Its complexity is definitely a big part of why so many reasonable people can end up disagreeing so vehemently... vanishingly few people understand how the whole thing works (and pretty much none of those who do are listened to by the politicians...)

Your question is good for another reason: you say "price" without qualifying whether you mean wholesale or retail (and, if retail, what individual households pay or what is experienced by industry). A lot of commentators and politicians routinely conflate the concepts to serve their own agendas in order to confuse non-experts.

If one looks first at the wholesale price, you're right that - in general - one would expect it to 'spike' when the gas prices shoot up. But on days when wind is dominant this has a minimal effect on retail prices, because the extra money paid to the wind farms (everybody gets the clearing price) is exactly offset by a reduction in the CfD payment. To repeat: consumers pay the same (high) price for most wind-generated electricity irrespective of the gas price.

So the interesting question, I think, is: what happens on days when the wind isn't blowing and gas generation is dominant? And here's the thing: if the price for gas-generated electricity (with carbon tax to account for the climate externality) is below the CfD strike prices, we're still ahead, even if it has spiked above its average. And because the CfD strike prices are so eye-wateringly high, this happens far more often than not.

Indeed, it was only for part of 2022 that the wholesale price was above the CfD prices and so the wind farms were paying money in to the system rather than taking out.

This chart from David Turver (who I learned a lot of this stuff from) is eye-opening in that regard: https://x.com/7Kiwi/status/2031657347433603581 (edited to provide clearer chart)

If the renewables fleet is supposed to be protecting us from gas price strikes, we're paying a VERY expensive premium for that insurance.

[gotwaz]

The key is factories ideally are mobile. Follow the winds. Come online and go offline when the wind blows. Use as much free energy as possible to hit yearly production targets and then take the rest of the year off.

[danatkinson]

Agile tariffs really only make sense if you have batteries. That way you can ride out the peaks by running off power generated in the troughs.

[account42]

But if batteries are economical then agile tariffs don't make sense for the providers.

[jonplackett]

What company are you with for that tariff? Do you have solar panels or something?