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Comment by mixedbit | Hacker News Reader

I wonder how practical it would be to build a system that would let home appliances cheaply overuse energy when there is a peak in wind or solar production. For example:

* Let heat-pumps heat homes to say 23C instead of 20C

* Let freezers decrease the temperature to say -30C instead of -18C

* Let electric water heaters heat water to say 70C instead of 50C, such water can then be mixed with more cold water

Such overuse would then reduce energy consumption when the production peak is over (heat pumps could stop working for some time until the temperature decreases from 23 to 20, etc.)

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You don't "build" such a system. You change the metering to follow supply, and everything else will follow naturally.

You'll have enthusiasts that'll do homebrew systems to take advantage of the economy, then you'll have companies catering to their (tbh, hobby), then you'll have products that are actually useful, then you'll see mass adoption. Like in everything else.

Trying to plan a huge strategy from the onset feels (and is!) daunting. Just make sure the price fits the reality, and savings will follow naturally.

Yeah right. Because building a freezer that goes to -30 C is as cheap as going to -18 C. It's much beefier hardware with a lot more insulation.

Likewise a heat pump can only boost so much.

This, like other environment related changes never happen by market forces. Not once. And small tweaks even on large scale produce small effects, insufficient for our needs.

Most normal home freezers have a way of setting temperature, e.g. mine can go from -16 to -24

So maybe -30 is difficult but it wouldn't be that hard to have the existing temperature range on new models be dynamic based on electricity pricing

> Because building a freezer that goes to -30 C is as cheap as going to -18 C.

For small sizes, yes it is.

But also, capex vs opex. Even if it's twice the cost, you only pay it once.

> You change the metering to follow supply, and everything else will follow naturally.

Tell me your wonderland where this has happened . . .

There are whole countries with wireless meters. There must be papers showing how much effect it has on consumer consumption? Ignore one-off examples, I'm interested in population level effects and statistics.

There's a program called Hilo [1] in Québec where it's using the Hydro-Québec Rate Flex D [2] to automatically stop the heating during peak demand.

> With Rate Flex D, you can save quite a bit of money, since most of the time in winter, you’ll be charged less than the base rate, except during occasional peak demand events, when you’ll be charged more than the base rate.

[1] https://www.hiloenergie.com/en-ca/ [2] https://www.hydroquebec.com/residential/customer-space/rates...

"Ripple control" is vintage technology - hourly usage meters are not necessary.

Everyone imagines that consumers would change their behaviour if they were given price information. In my experience, I've yet to see any good data showing that on average consumers save electricity due to smart meters.

In New Zealand, I think the power companies design their consumer products to be unhelpful (what's the equivalent term here for dark patterns in marketing?). I believe few consumers watch their instant usage or review their hourly usage. Personally I changed away from a plan that used spot prices (after seeing the debacle from snow in Texas, and realising the rewards were low and that judging/managing the risks was hard).

> Tell me your wonderland where this has happened

Plenty of grids had started paying consumers for excess solar generation exactly in this manner.

Already kind of in place. I’m on the Octpus agile tariff that gives different electricity tariffs every 30 minutes - with 24 hour notice if tomorrow’s prices.

Whenever electricity prices go negative I have automations to force-charge my solar batteries from the grid, turn on hot water heaters in my hot water tank (normally heated by gas etc. ).

Having just had solar and a battery fitted by Octopus I'm interested - would you mind sharing what you use for automation here please?

Sure, I use Home Assistant running in a little raspberry pie in the lift.

There is an Octopus Integration that exposes current prices (and much else) to HomeAssistant.

There is another Integration that works with my solar panels and another that works with my batteries and can change mode (self use, force charge, force discharge etc.)

So from there it’s really just a question of setting up some if-then automations to turn on smart switches, charge the batteries if prices go negative.

You can also gradually add more nuanced automations like turning on water heaters if the panels are generating more than 1kW and the batteries are over 90% charged.

I’m not a programmer, it’s all fairly easy to do.

Thank you, that's really useful.

Not op but may I suggest looking at Home Assistant, Octopus Energy Addin and Predbat: https://springfall2008.github.io/batpred/energy-rates/

Thanks very much.

To add, so called 'dynamic energy contracts' are getting more and more popular, at least in my native Netherlands. The European day-ahead electricity market switched to 15-minute price blocks this month, to more accurately follow the supply and demand.

The market for power imbalance was already on 15 minute blocks.

I'm using a HomeWizard smart plug [0] to enable my electric boiler to only run during the cheapest hours of the day

[0] https://www.homewizard.com/energy-socket/

I do similar, but without the batteries.

I just have Home Assistant turn on everything: dehumidifiers, heaters, lights, set the freezer thermostat to -25c.

So far I've earnt about 10p, but the real saving comes from having a little bit of thermal inertia to carry through to when prices are higher.

You might find the crossover for hot water heating is higher than 0p; your boiler is likely only around 70% efficient. So at 6p/therm for gas, you'd break even with resistive electric heating at around the 10p/kWh mark.

You should absolutely re-run these numbers to be sure, but you might find you can use electric heating far more often than you might currently be doing.

The only thing you would have to do to make this happen is to change electricity pricing from a fixed rate to a dynamic rate based on actual market conditions, along with a standardized way of accessing current pricing. This would drive consumers to shift their behaviors to take advantage of cheap prices, and smart appliances could access the price feed to make decisions like the ones you mention. Another simple one is washing machines, dryers and dishwasher offering to delay their start time to coincide with the cheapest energy price within X hours.

The issue is that most consumers don't like unpredictable prices. You can make a crude approximation by having 2-3 fixed rates for different times of day, but that leaves a lot of potential on the table

Electricity contracts with 1-hour pricing are already pretty popular at least in Finland, even for consumers. I myself have one.

Plus large parts of Europe are currently transitioning to more granular 15-minute pricing: https://www.nordpoolgroup.com/en/trading/transition-to-15-mi...

You can still get fixed tariff electricity contracts but you'll end up paying a bit extra in return for greater predictability…

Even if such a system was set up, it would take years before the appliances where all updated to take advantage of it.

And in the meantime it would be very unpopular for people who can't just afford to renew their otherwise fully functional appliances.

For your old appliances you still pay the same on average. A fixed price contract isn't cheaper, it just smooths prices into a long-term average. And many of the changes can be done manually. On your old dishwasher or washing machine you decide when they start, and most of them even already have buttons to start with a fixed-time delay. Instead of starting them at the end of day you can just start them when the wind is strong or the sun is shining, or watch the price feed. You even get to feel smart for saving money

I agree on the popularity, but you'd absolutely see an effect even without anyone buying new appliances

Years isn't that long.

The aim is net zero by 2050, lifespan of a fridge-freezer is about 10 years. Even assuming designing a system and putting it in place took 5 years, that's still enough time to have most appliances on it by 2040.

Given the current energy prices, it probably even makes sense to replace appliances sooner than their normal lifetime. My fridge-freezer is only 5 years old, but if it broke today and cost more than ~£150 to repair, I'd end up saving money by replacing it.

Each year is a significant fraction of a government mandate though.

they are installing now smart meters with sim cards in Greece, and of course everyone started complaining, shaming the gov, claiming corruption, etc...

General population doesn't understand that fixed pricing includes an extra cost which is the risk that the electricity provider has to account for. That risk has a calculable price, which is passed down to the consumers. But because it's baked in the flat rate, nobody complains.

Smart/dynamic pricing actually benefits the consumer.

It does, but people are really bad at understanding it.

It's like how there's a substantial portion of the population that counts the best commute time ever as their commute time, and are perpetually late. "How can it take 30 minutes to get to work, one time it was only 15!" - ignoring the reality of traffic, subway delays, etc.

> Smart/dynamic pricing actually benefits the consumer.

No it doesn't. The customer has low risk appetite and would rather pay a premium for predictability.

Clearly the consumer should automatically trade futures as a hedge!

> The issue is that most consumers don't like unpredictable prices.

The key is to not take this away; make it so that those who want predictability can get it (but they end pay more for the privilege) but those who want to try to "game the system" can (and incidentally help with the overproduction problem).

Done well, things like Powerwalls, thermal mass storage, etc could absorb quite a bit of load during peak production times, reducing load at inopportune times.

This will probably take a little longer for private use, but the industrial sector is already doing this. Cooling chambers being cooled down further during cheap electricity prices (or sunshine when they have their own solar) or storing heat/"cool" underground

When I was working with NREL back in 2017, they were thinking about coordinating water heater electricity use with a “smart grid.” Each device attached to the smart grid would measure the electricity spot price and would “store” energy to minimize cost. At the time the goal was to reduce peak load on the grid, but the same ingredients to maximize power use from intermittent power sources.

For example, see https://docs.nrel.gov/docs/fy23osti/82315.pdf

You have to get the energy to the appliances though, and there is the bottleneck.

It does looks like it will make some sort of sense for compute workloads to move around to be at locations near surplus energy generation. As someone else mentioned bitcoin mining (with the benefit of heat generation) could also be used, but if this practice becomes widespread the attachment of bitcoin pricing to what is in effect negative local energy prices may prove to be a structural problem with it.

I really don’t think that that’s the bottleneck. Peak demand is much higher than average demand. There is a lot of leeway in moving around domestic demand

This literally is the bottleneck which wastes the energy and is so stupidly expensive in the case of Britain (and Germany).

The issue is lots of renewable generation far from places where it is used and not enough transmission capability.

This is called curtailment and is really, really bad. Energy providers need to pay the windfarms for the energy that they (the grid operators) fail to transmit to where it is needed, and they have to pay backup generation (usually gas) at the place with the load.

It’s an issue right now because we lack the ability to steer demand. Connect a few million electric cars and heat pumps to the grid and allow the grid operators to talk to them and the issue is much less severe.

No. Steering demand will not work. Unless by steering demand you suggest forcibly moving millions of people to Scotland.

You have an intermittent power source (wind), far removed from where the energy is needed, and you do not have sufficient electric transmission capacity.

Heat pumps or EVs far removed from the source of generation will not do you any good. You need load where the energy is produced or you need more transmission capacity.

The situation GB has is that there is load, and there is enough renewable generation on the grid to meet that load, however they do not have the capability to bring the electricty to where the load is. You can lessen the demand, but the generation would not get less through that. The only benefit of that would be that you wouldn't have to spin up gas plants, but the same amount of wind energy would still be lost.

There are multiple issues, transmission is one, but supply+demand being out of sync is another

E.g peak solar is around 2pm, peak demand is around 7pm

Grid storage (including EVs and smart heat pumps) absolutely help with this second problem

With flexible rate agreements, that's already possible, and some DIYers already are doing this - the problem is the interfacing. Heat pumps (and central heating systems in general) are notorious for being walled gardens, most freezers run on analog technology (i.e. a bi-metal strip acting as a thermostat).

I'm in the market for a heat-pump based system and I'm 100% worried about lock-in/walled gardens.

Take Google, which should have plenty of money and systems to provide long-term support, is regularly axing older products. (Of course, Google has a history of such actions, but they don't have to EOL products that should have long life-spans. Plenty of company won't really have a choice if they are facing bankruptcy, etc.)

You are correct. Some devices expose local API's, most have walled garden cloud API's

Before buying a device, it is a good idea to check if there are open source adapters for it for Home Assistant, those usually show if it can be controlled easily and preferably without cloud.

For heatpumps/heating in general - we have a after market-product here that you can install in your old "dumb" central heating system - you connect it between the outside thermometer and your boiler/pump/what have you. It then fiddles with the outside temperature readings as to trick the pump to run harder/easier depending on the electricity price (and thus in extension, towards peak production). I used it in my previous house and it worked well! (no affiliation except as a former customer, but the product in question _I used_ is called ngenic tune [0])

[0] https://ngenic.se/en/tune/

It's practical enough that this is how it works now in many (most?) parts of Europe at least. Electricity at the wholesale level is priced hourly or quarter-hourly and households often elect to have a correspondingly hourly priced eletricity contract & program their appliances/ev charging/whatnot to follow the price.

See eg https://www.euronews.com/business/2025/02/20/fixed-vs-variab...

We have this system in Finland and whilst I was sceptical at first, it works much better. Electricity prices are published about 24h in advance for 15m intervals (was 60m up until 2 weeks ago). You can therefore time your usage dependent on demand on the grid (which is correlated to production of course).

We've saved 100s of euros annually on our electric bill by limiting sauna, washing machine + dishwasher to low-cost hours. Sometimes it's impossible and it's days at a higher rate - but for a 2 person household it's costing us 15-20e a month (+ additional transmission costs)

https://en.wikipedia.org/wiki/Radio_teleswitch

> This includes switching between 'peak' and 'off-peak' meter registers as well as controlling the supply to dedicated off-peak loads such as night storage heating

1980's technology, recently switched off, I presume for internet based alternatives. The exact same principle applies, beats batteries as hot water tanks and storage heaters already exist.

Smart thermostats and water heaters can to that to some extent. Heat or cool the room a little more and run the water heater when electricity is cheap, so that they don't have to run when it is expensive. Of course, electricity price matches supply and demand.

Other options could be delayed start for large appliances like washing machines and charging electric vehicles. EVs have even been proposed as a distributed battery system to smooth out electricity use.

This is called demand/response: https://www.openadr.org/

A lot of thermostats support it

Is there a list of supported thermostats? Would be very interested in implementing this ahead of the winter.

Already works, you tie in your battery storage to lower costs. That already works.

The problem here is

1) the excess power is not near the demand

2) the cost of electricity near the excess power is no lower than where there's no excess

3) nimbys prevent the extra interconnects being built which equalise power availability and power demand

Already have thermostats that move based on signals from the utilities. There were some early pioneers in this stuff over 10 years ago in the bay area. They also aggregated the power to bid it, but I imagine they could aggregate to buy as well.

We have a low-tech version of something like this in South Australia: we pay the wholesale rate for electricity, which updates at 5 minute intervals. During the day when there’s oversupply of wind and solar, the rate is super low or even negative, which we take advantage of to charge an EV (and we’ll be adding a home battery soon).

The power company can integrate with car chargers and battery controllers to control all of this automatically, though we don’t bother - just check the app for the cheapest/greenest times and schedule the car to charge then.

It’s allowed us to switch to an EV without even really noticing any extra power cost for charging it.

Personally, homes and freezers should have a consistent temperature; if there's ways to store the excess heat / cold somehow that'd be neat. But for homes, the best ways to store excess energy would be batteries and electric cars, or worst case sink heat into underground storage.

The electric water heaters are a good idea, but you'd need the space for extra storage. There's existing heat exchanger systems with e.g. rooftop / sunlight water heating systems, if excess cheap energy could be used to also heat that storage you'd have something.

It would be much more effective to even out things , and trivial (engineering wise) to stop wasting the outputs of all these heat pumps by effective integration. Ie dump heat removed by ac or freezer into hot water heating, etc

I'm always highly amused when people have heated pools next to large outdoor ac units. They could probably dump all the heat from house into it the entire summer and not have a meaningful effect on the temperature

My parents had a off-peak hot water system when I was growing up. The insulated tank would fill and heat up during off-peak hours (i.e. late at night), and merely keep it warm during the rest of the day.

The downside was that once the hot water was gone, we had to wait until the next day for more. The last person to shower occasionally got a cold shower.

On-demand systems win here.

Good water heaters are key. Mine is 200 liters and I've experienced cold water exactly once in three decades: One day 3 guests took hour-long showers each. Normally a family of five will never experience cold water.

The one I'm getting now has two coils, one to quickly heat water at the top half, the second to heat from the bottom - they're never on at the same time. Internal heat around 75 C, mixed to cooler on the way out, and it can keep hot water for 2 weeks if disconnected from power.

> 3 guests took hour-long showers each

WTF showering for one hour? That's a great way to quickly become persona non grata in my house.

Yeah.. I'm more of the "4 minutes" type myself, so I kind of didn't foresee that.

This is already happening with electric car charging. However, part of the reason this can't apply here is that the UK doesn't have regional pricing. For this to work you'd need to vary people's prices depending on which pylon they're connected to.

A lot of thermostats already do that. Unfortunately these programs are not terribly popular. People see that the temperature is off and complain. Look up people talking about Nest Energy Shift (different but somewhat similar idea), most comments are quite negative.

I work for a company that does exactly that (for heating systems, especially heat pumps). If anyone is interested: https://www.kapacity.io/

I'm on the octopus agile tariff that has 30 minute pricing and an API to query it. Prices for tomorrow published at 4pm today. So the pricing bit is sorted. Just need to make the devices understand it now.

You can get price into home assistant and control any kind of device that it supports it, or hack it on your own.

This is not the issue discussed here. The generated power can not be transmitted to where it is used.

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