A "sustainable app" carries a double meaning. An app that enables sustainability — CO2 tracking, ESG reporting, energy monitoring, circular sharing platforms — and an app that is itself built sustainably, with code and hosting that waste no energy. We build both, and preferably at the same time.
When clients call us about a "sustainable app", they usually mean one of two things. The first group has a product or business goal: they want to help their customers reduce their footprint, they need to report on impact credibly under the CSRD, or they are building a circular business model that software will carry. The second group is driven internally: they don't want to build an application that will quietly consume excessive energy on awkward infrastructure, and they want to be able to show that their digital products won't become the bottleneck in their own sustainability reporting at the scale of thousands of users.
In practice, those two meanings tend to coincide. An organisation that is serious about its sustainability story cannot afford to launch an app that measures a user's carbon footprint while itself running unnecessary calculations on a hyperscale GPU because a developer once set it up that way. We build app development projects in which the substantive sustainability functionality and engineering discipline evolve in parallel.
Our clients in this space are ESG-conscious SMEs and enterprises, sustainability start-ups, energy companies, circular economy players, municipalities and NGOs. What they have in common is that they don't want a marketing app with "100% green" in the hero and a footprint that nobody in practice verifies. They want an application whose claims, data model, calculation rules and hosting choices hold up against an external auditor, a Green Claims Directive investigation or a sceptical client.
Depending on who the user is — consumer, employee or compliance team — the focus of the functional design shifts. In the first conversation, we advise which form suits your challenge.
A mobile app that shows your end users their carbon footprint, tracks their energy use, logs their recycling habits or lets them take part in a circular platform. A personal dashboard, push notifications at relevant milestones, and integrations with smart meters, public transport data or bank PSD2 feeds. Also read how we use AI development to generate personalised, actionable recommendations rather than generic tips.
An app for your sustainability coordinators, location managers and data suppliers to collect data points, validate them and deliver them to the reporting platform. Intended as a smart layer around your existing CSRD tooling, or as a core component of your own sustainability stack. It follows directly on from our page on building CSRD-ESG reporting software.
A marketplace, sharing platform or take-back app that makes the physical economy circular: refurbished electronics, swap platforms, returns logistics, reusable packaging or a second-hand stream for your own products. Inventory, product identity via a digital product passport, quality reporting and integrated payments. Links to our page on a digital product passport.
Eight functional building blocks we often build or integrate. Which ones you need depends on your target audience, your reporting obligations and the extent to which you want to map the physical world.
For consumers, a mobile app that builds a credible CO2 estimate from public transport data, bank transactions, energy meter readings or manual input, with clear source attribution on each line so a user understands where the figure comes from and which part is an assumption. For businesses, the same principle applied at the level of product, contract or service, fed by internal data and sector emission factor libraries.
Real-time energy consumption via the P1 port, smart meter APIs, or building management systems (BACnet, KNX, Modbus). Aggregation to daily, weekly and monthly levels, anomaly detection when an installation draws unusually much power, and integrations with dynamic energy tariffs so users can see peak and off-peak hours. See also building energy software for the broader data approach.
An app that records commuting, business travel and corporate air travel through GPS detection, NS Business, mileage claims or HR mobility data. Output goes to the employee (personal insight) and to the employer (aggregated, GDPR-compliant), so that scope 3 category 7 (employee commuting) and category 6 (business travel) appear clearly without shadow spreadsheets.
An app that allows consumers or employees to drop off, scan or register waste, packaging or products. QR or NFC tags on packaging, a map layer for drop-off points, reward schemes where appropriate, and handover to your processor with verifiable material flow records for the Environmental Management Act (Wet Milieubeheer) and Extended Producer Responsibility.
An app for customers or buyers that shows, per product, its origin, certifications and environmental impact: organic, fair trade, FSC, recycled content, local production. The underlying data comes from your PIM, supplier self-declarations or a DPP platform. It helps you make claims that comply with the Green Claims Directive, without marketing claims drifting away from what is actually recorded in your systems.
A marketplace for refurbished, second-hand, swap or rental goods. Inventory management at unit level rather than SKU level, a quality score per unit, a returns flow with payments, and integration with your brand platform so the circular flow isn't a separate sub-site but part of your customer experience.
An app or dashboard layer for sustainability teams and management that displays current scores on material KPIs, progress towards reduction targets and outstanding data points. Built so that the figures on the dashboard are exactly the same as those used for ESRS reporting or stakeholder updates, with no parallel version of the truth in PowerPoint.
For consumer and employee apps: carefully designed nudges, milestones, comparisons with cohort averages and small rewards that genuinely change behaviour without drifting into greenwashing. We work with behavioural science experts on this and test every nudge for actual change, not vanity clicks.
The code, the architecture and the hosting determine whether an app requires a few watts or a few tens of watts per user. The difference scales with your user numbers, and is usually free to achieve when built in from the start rather than retrofitted.
Many apps do work on a server that could just as well run on the device itself: data transformations, small calculations, simple filters. We design APIs so that the device does as much of its own work as possible, and only genuine aggregations or multi-user operations run through the backend. Fewer server calls mean fewer running processes, less network traffic and less energy per session.
A CDN layer, browser and app caching, and beneath that server-side query caching for data that doesn't need recalculating on every request. In practice, a product catalogue that changes once a day doesn't need to be fetched from the database on every page view. At scale, this saves an order of magnitude in compute, and therefore energy, per user served.
Resources load only when they come into view. Images served in AVIF or WebP, automatically scaled to the device. A considered dark mode implementation that genuinely lights fewer pixels on OLED screens. No JavaScript frameworks that download more megabytes than the app gives back in functionality.
Apps that use GPS, sensors or background sync should do so with consideration for battery life. We batch network requests, use push mechanisms instead of polling, and build core tasks to work offline so a user on a train, on a platform or inside a building without coverage doesn't suddenly find the app online-only and loses data.
Hosting with providers that are transparent about their energy sources and that run in regions with a cleaner grid (for example Azure, Google Cloud or AWS regions with demonstrably low grid carbon intensity). No "100% green" claim without evidence; instead, a reasoned choice of region, transparency about PUE and, where relevant, locations with waste heat recovery. This ties in with the broader idea from our page on AI development: deploy heavy models only where they genuinely add value.
Many architectures are built to run large. We design them to run small too, where possible: serverless functions that scale to zero under low load, batch processes that run overnight on cheap (often cleaner) capacity, and monitoring that lets us spot and switch off unnecessary workloads.
A production-ready sustainable app, plus the documentation and engineering justification your own sustainability, IT and marketing teams need to substantiate the claims.
With OneDayBuild, we turn your idea into something tangible in one day for €1,150, so you can see whether further development is worth the investment. Decide to go ahead with the full build? Then we credit the full cost.
Explore OneDayBuild →Many sustainability applications can perfectly well start from off-the-shelf software (Plan A, Position Green, EcoVadis, Sustainalytics, Watershed, or a calculation tool from your industry body). We only recommend custom development when you recognise one of these patterns.
A carbon footprint app for an energy company, a returns app for a brand retailer, a sharing platform for a transport operator: users see the app as your product, not as a third-party tool. Custom development makes sense because the visual identity, tone, flow and integrations are woven into the rest of your stack.
An NGO collecting volunteer data in a way that fits no off-the-shelf package, a municipality combining neighbourhood-level energy data with waste streams, or an agricultural co-operative reading soil sensors. No SaaS product is built for your particular data combination.
You already have, or are building, a serious CSRD platform and want a mobile input app for local data suppliers, or a dashboard app for the board. The app must follow exactly the same data discipline as your reporting layer, which almost always calls for custom integration. See also our page on CSRD software.
A take-back stream, sharing platform or refurbished marketplace whose entire commercial logic lives in the app. No SaaS building block fits a new business model; the app and the backend are the business.
A conversation to understand what you mean by "sustainable": functionality, engineering or both; which compliance context applies (CSRD, ESPR/DPP, Green Claims Directive, GDPR); who the user is; and which claims your marketing and your legal team will later need to substantiate.
Workshops with your sustainability team, data owners, product management and, depending on scope, your legal or compliance department. We map the data model, identify source systems and establish which claims the app will actually make. At the end: a validated scope, a first screen flow, and a document listing the sustainability claims together with the sources that support them.
A working build every two weeks that your team and a group of real end users can test. We integrate with source systems early (smart meters, PSD2, ERP, supplier APIs) so integration risks don't blow up at the end. A first publishable version typically comes out of the first sprint cycle; further features and integrations follow after that.
Completion of the DPIA, penetration testing, and a claims review in which we check, for each sustainability claim in the app, whether the source rule holds up and whether the wording is compliant with the Green Claims Directive. The aim: no surprises when a journalist, a regulator or a critical customer asks "how do you know that?"
App Store publication, a phased rollout to your target group, and monitoring of both functional KPIs (usage, retention) and technical KPIs (energy consumption per session, API load, error rate). Further development in response to new reporting requirements, changed emission factors and user feedback.
What clients in this field usually want to know before we start.
A free, no-obligation half-hour introduction. We listen to your challenge — functionality, engineering, or both — and point you in a useful direction, even if an off-the-shelf platform turns out to be the better choice. See also app development for our broader approach.
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