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29 Dec 2026
Dynamic electricity tariffs: how to design an app people actually use
How to design an app for dynamic or hourly electricity prices: what to show now, the next cheap window, what to run and what it saved.
Short answer
Answer one question before anything else: is now a good time to use power? Then show the next cheap window, what to run in it and what it saved. Automate the big loads by default and keep manual control one tap away. A price chart alone changes very little. A clear verdict plus automation changes a lot.
When Spain moved regulated household tariffs to hourly prices in April 2014, Red Eléctrica started publishing the next day’s prices every evening at around 8:15 pm. Twenty-four numbers, delivered after dinner, to people who wanted to know one thing: can I put the washing on? It’s a bit like answering “are we there yet?” with a spreadsheet of GPS coordinates.
Most of Europe is now catching up. According to ACER, the EU energy regulators’ agency, 66% of EU households have a smart meter, but only 7% are on a dynamic price contract. The law and the hardware are mostly in place. What’s missing is a product people want to live with.
At Dtail Studio, a Barcelona design studio working with HealthTech and renewable energy startups, we think about this problem through our work on Cubee, an energy management startup whose brand and product we designed (case study).
Who can get a dynamic electricity tariff?
In the EU, any household with a smart meter can ask for one. Article 11 of the Electricity Directive (EU) 2019/944 requires member states to make sure customers with a smart meter can sign a dynamic price contract with at least one supplier, and with every supplier that has more than 200,000 customers, as set out in the CEER’s implementation guidance.
Germany went further. Since 1 January 2025, all electricity suppliers must offer dynamic tariffs to customers who have a smart meter, not only the large ones.
There’s a design brief hiding in the law, too. Article 11(2) says customers must be “fully informed by the suppliers of the opportunities, costs and risks”. Read it again and it’s a list of screens. Opportunities is your savings view. Costs is your price view. Risks is what happens on the day prices spike, and that’s the screen most apps forget to design. Few people expect to find a sitemap in an EU directive.
Why don’t price charts change behaviour?
Because they ask people to do maths at the exact moment they want an answer. Raw prices reward the few who enjoy spreadsheets and lose everyone else.
The evidence on manual response is modest. A study in The Energy Journal modelled Swedish households on hourly prices and found a maximum peak reduction of about 3%, with little shifting between hours. When Octopus Energy studied its Agile tariff in the UK, 28% of 149 customers made a statistically significant change to peak use, and peak consumption fell from 16% to 11.5% of the daily total. Real, but these were early adopters who chose a dynamic tariff on purpose. The people who read the manual for fun.
Automation is a different story. In a Nesta and Centre for Net Zero trial where heat pumps were controlled remotely during peak events, heat pump electricity use fell by an average of 74% in the two-hour window. 81% of participants were satisfied with their home’s temperature and only 9% opted out of events.
So the app’s job is to make the right thing happen, explain it in one line and get out of the way. Watching prices is optional.
What must a dynamic tariff app show?
Four answers, in this order: now, next, what to run, what it saved. Add a fifth for risk. Everything else lives one level down.
Now: Is now a good time?
What the app shows: A verdict in words: “Good time”, “Normal”, “Wait if you can”, with the price underneath; Design notes: Relative to today, not absolute. Colour plus text, never colour alone; Common mistake: Leading with a price per kWh to three decimals.Next: When is the next cheap window?
What the app shows: Start and end time, how long it lasts, how much cheaper it is than now; Design notes: A countdown beats a chart. Show tonight and tomorrow, nothing further; Common mistake: A 24-hour bar chart with no labels on the bars that matter.What to run: What should I do in it?
What the app shows: Named appliances and devices: car, heat pump, battery, dishwasher; Design notes: Big loads run automatically, small ones get a nudge with one-tap scheduling; Common mistake: Generic tips (“use less in the evening”).Saved: Did it work?
What the app shows: Euros saved this week against a fair baseline, such as the user’s old fixed tariff; Design notes: Admit the bad days. Trust survives a loss you explained; Common mistake: Savings with no baseline, or only in kWh.Risk: What if prices spike?
What the app shows: An alert in plain words, what the app has already done, what the user can still do; Design notes: Set limits up front: minimum battery level, minimum temperature, maximum price; Common mistake: Finding out from the monthly bill.
Units matter here. If you’re tempted to put kWh on the home screen, read our post on designing energy apps around kilowatt hours first. Nobody has ever bragged at a dinner party about their kWh.
How much should the app automate?
Automate anything with a battery or thermal mass, and suggest everything else. A car, a home battery or a heat pump can wait an hour without anyone noticing. A dishwasher still needs a person to load it, at least for now.
Good automation follows three rules.
Set limits once, in human terms.
“Car ready by 7:30 with at least 80%.” “Never below 19 degrees.” The app works inside those limits and never outside them.Say what it did, and why.
“Charged from 2:00 to 4:30, the cheapest hours tonight. Saved €1.40.” One line, written like a person.Make override instant.
One tap to “charge now”, no confirmation maze. People only trust automation they can switch off.
The ACER estimate of up to €270 a year in potential household savings depends on consumption patterns. In practice, that means it depends on whether the big loads move. Manual effort alone rarely gets there.
How do you design for people who don’t care about electricity?
Assume nobody wants to think about it. Design for the person who opens the app twice a month, not the one who opens it twice a day.
That means plain words before numbers, large type and strong contrast, and notifications only when there’s a decision to make. A household on a dynamic tariff may include a teenager, a partner who never installed the app, and a parent in their eighties. Our notes on designing tech for older adults apply directly: if a screen needs a legend to be understood, it isn’t finished.
Treat the price itself like a nutrition label. It should be there, accurate and easy to find, but nobody chooses dinner by reading one first.
What did Cubee teach us about energy products?
That energy technology has to feel approachable without losing credibility. That’s true for the brand, and it’s true for every screen.
Cubee is an energy management startup. When they came to us, the technology was strong but the visual presence was scattered. Between January and April 2024 we designed their logo, brand strategy, identity, packaging and product design: a geometric symbol system built on energy flow and connection, a logomark that balances precision with warmth, and a grid and type logic that scales from decks to digital product to the box.
“Dtail helped us launch with a brand and product that stood out instantly,” says David Vondracek, Founder and CEO of Cubee. Cubee now counts more than 2,000 installations, which is their team’s doing. A good brand just makes the second conversation easier.
If you’re at the stage before the product, our guide on how to brand a clean energy startup covers the brand side.
FAQ
What is the difference between a time-of-use tariff and a dynamic tariff?
A time-of-use tariff has fixed price bands set in advance, such as a cheaper night rate. A dynamic tariff follows the wholesale market, so prices change hour by hour and day by day.
Do customers need a smart meter for a dynamic tariff?
Yes. In the EU, the right to a dynamic price contract under Article 11 of Directive 2019/944 applies to customers with a smart meter.
Should the app show prices or plain words?
Both, in that order. Lead with a verdict in words and keep the exact price one line below it for the people who want it.
How should the app handle a price spike?
Warn early, act within the limits the user set, and tell them in one line what it already did. Never let the bill be the first notice.
A test you can do today
Open your app’s home screen, hand the phone to someone who has never seen it and give them five seconds. Then ask: “Should I run the dishwasher now?”
If they can’t answer, your home screen is showing data, not a decision.
Building an energy product that should feel this simple? Let’s talk.
About the author: Stan Hristov is a partner and Creative Director at Dtail Studio, a senior brand and product design studio in Barcelona with 16+ years and 300+ projects behind it.
Sources: ACER, Energy retail and consumer protection monitoring 2026 · ACER, Energy retail and consumer protection monitoring 2025 · CEER, Dynamic price contracts implementation Q&A · ADVANT Beiten, Energy law changes as of 1 January 2025 · Red Eléctrica, hourly electricity prices press release (2014) · The Energy Journal, Understanding hourly electricity demand (executive summary) · Solar Power Portal, Octopus Agile study · Nesta, heat pump remote control trial
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