Web Development |

Green Coding: A Developer's Guide to Sustainable Software

Nick

November 12, 2025

tl;dr quick summary

Green coding is about writing and running software that minimizes energy use and carbon emissions. Since the tech industry accounts for around 4% of global greenhouse gases, developers can make a real impact by optimizing code, managing data efficiently, and choosing green infrastructure. Measuring emissions with metrics like **Software Carbon Intensity (SCI)** and tools such as **Ecograder** or **CodeCarbon** helps track progress. Even small optimizations like removing unnecessary code or reducing data transfers can save significant energy at scale. **In short, efficient code is sustainable code.**

The Hidden Cost of Code

The tech industry might seem intangible, but its carbon footprint is very real, roughly 4% of global greenhouse gas emissions. Every API call, every line of inefficient code, consumes energy somewhere. The good news? As developers, we have the power to make a difference and this post will show you how to start.

What Is Green Coding

Green coding refers to the practice of designing, developing and optimizing software in ways that minimize energy consumption and thereby reduce its carbon footprint. For example, this can mean optimizing database queries, caching results, reducing unnecessary background processes, or even choosing energy-efficient frameworks. Green coding is part of a greater movement, Green IT, which is aiming to reduce the environmental impact of all IT Systems. This includes software, hardware, data centers, energy sources and the entire lifecycle of these components.

Before we go further, we need to define a few important terms:

Carbon Intensity (CI): Measures the amount of CO₂ equivalent (CO₂e) emitted per unit of energy consumed. In other words, it shows how “green” or “dirty” the energy is in terms of greenhouse gas (GHG) emissions.
Embodied Carbon (EC): Refers to the total amount of CO₂e emitted during the entire lifecycle of a material or product before it is used. This includes emissions from raw material extraction, manufacturing, transportation and construction.
Carbon Equivalent (CO₂e): A unit that measures the environmental impact of different GHGs by comparing them to the same amount of CO₂. For example, 1 ton of methane (CH₄) has roughly the same warming effect as 25 tons of CO₂, so it equals 25 tons CO₂e.

To measure what our software consumes and emits, we need metrics to visualize and compare. Metrics like Software Carbon Intensity (SCI) help quantify a software system’s carbon footprint. Thinking green is important, but taking action is essential. To make your software truly sustainable, you need to measure its energy consumption, understand where it’s most wasteful and track the impact of every optimization.

How to Implement Green Coding

0. Choose Efficient Architecture and Green Hosting (before coding)

Before you write a single line of code, it’s important to consider the architecture of your system.

Right-size your resources

Most applications today run on cloud servers, so when setting them up, focus on reserving just the resources you actually need. Over-provisioning, reserving more than necessary, wastes energy because idle servers still consume power and also increases hosting costs. Another approach is to use serverless solutions, which automatically allocate only the memory and processing power your application needs.

Pick green hosting providers

Even the most optimized software still needs a sustainable home. Choosing a green hosting provider can further reduce your software’s carbon footprint. Look for providers that rely on renewable energy and operate energy-efficient data centers and once you’ve chosen a provider, select the best location for your data center to minimize your software's carbon intensity. If you want to learn more about green hosting, check out Michael’s article: "Green Hosting: A Sustainability Comparison".

1. Optimize Your Code for Energy Efficiency

Some powerful ways to increase your software's energy efficiency are optimizing algorithms and writing clean, maintainable code. Efficient code paths require fewer computations, which directly reduces CPU work and therefore energy usage. Clean and maintainable code helps here, because it is easier to understand, refactor and optimize over time, making performance improvements more likely and more sustainable.

A practical example is the way you structure your database queries. Selecting only the necessary columns and relying on indexes avoids scanning entire tables, while poorly optimized queries waste processing power and energy. In fact, a study found that inefficient SQL queries can consume significantly more energy compared to optimized ones simply due to unnecessary full-table scans. Thoughtful code design is not just good engineering practice, it’s also a concrete step toward greener software.

2. Manage Data & Network Usage

Did you know? According to the HTTP Archive’s “Page Weight” report:

Since 2010, mobile page weight has increased by ~1700%.
At the 90th percentile, desktop pages weigh nearly 12.2 MB and mobile pages nearly 11.1 MB.
The average web page size now hovers around 2.7 MB+ and continues to grow. These statistics show that despite awareness of performance and efficiency, digital systems continue to grow in size and with that, their environmental impact.

Every byte transferred consumes energy, on your servers, across the network and on the end user's device. Minimize data transfers by sending only what’s necessary, compressing files and paginating large API responses. Regularly cleaning up unused data, like old backups or logs, avoids unnecessary storage overhead.

Efficient caching also reduces redundant requests and saves energy. For example, a blog can cache rendered pages so repeat visitors don’t trigger database queries each time. Hosting servers closer to users, or using CDNs, similarly reduces long-distance data travel, lowering energy use.

3. Measure and Monitor Energy Usage

You can’t improve what you don't measure and that’s especially true for sustainability. Measuring your software’s energy usage and carbon footprint helps identify where optimization makes the biggest impact.

Standardized Metrics

The Green Software Foundation (GSF) defines a unified metric called Software Carbon Intensity (SCI), which quantifies emissions relative to software usage. SCI can be broken down into three key factors that determine how efficiently software uses energy and contributes to carbon emissions:

Carbon Awareness: Measures how software considers CI when using energy. For example, energy-heavy tasks can be scheduled when renewable energy is abundant, so the software’s energy use has a lower carbon footprint.
Hardware Efficiency: Measures how well software uses physical resources like CPU, GPU, memory and storage. High efficiency means doing the most work while using as little energy as possible.
Software Efficiency: Measures how well the software itself is optimized. Efficient software reduces or eliminates unnecessary computation, memory usage and data transfer, using less energy to perform the same tasks.

Calculation of SCI

Example: Measuring SCI in Practice: Farm Insights on Raspberry Pi

To see how Software Carbon Intensity (SCI) can be applied in the real world, the Green Software Foundation published a case study called Farm Insights.
It’s a small-scale agricultural monitoring system that runs on a Raspberry Pi using sensors for temperature, humidity, sunlight and soil moisture, all powered by a lightweight .NET Core app.

The developer measured the energy consumption and emissions over one year:

Metric	Description	Value
Energy Usage	Power consumed by the Raspberry Pi and app	0.003 kWh per day
Carbon Intensity (CI)	Location-based emissions factor	0.713 kg CO₂e per kWh
Embodied Carbon (EC)	Estimated using smartphone averages	55 kg CO₂e
Functional Unit	Per Raspberry Pi device	-

The SCI calculation followed the formula:

Where:

(E) = Energy consumption (kWh/year)
(CI) = Carbon Intensity (kg CO₂e / kWh)
(EC) = Embodied Carbon (kg CO₂e per device) Plugging in the measured values and annualizing the embodied carbon over the Raspberry Pi’s lifespan of 8 years:

This means that running one small Raspberry Pi-based application continuously for a year has roughly 7.7 kg CO₂e/year.
Over its lifetime (~8 years), the total SCI sums to:

For context, this annual SCI is equivalent to driving a typical car about 39 km (based on ~0.197 kg CO₂/km for a 2020 Toyota Corolla).

This case study highlights how measurement reveals hidden impacts even in small systems.
By understanding and tracking SCI, developers can experiment with improvements, for example, scheduling tasks when renewable energy is available or using more efficient hardware and directly see how those decisions reduce emissions.

Tools for Measuring Impact

You don’t have to start from scratch, there’s a growing ecosystem of tools to measure and monitor digital emissions:

🔍 Ecograder: Analyzes the impact of your website on the environment based on a variety of performance, efficiency and user experience factors and hosting choices
📱 Android Power Profiler: Allows developers to monitor app-level power usage directly on Android devices.
🟢 CodeCarbon: Estimates energy usage and carbon emissions of Python code; integrates with ML workflows.
⚡ Kepler: An open-source tool from CNCF that measures real-time power consumption of Kubernetes workloads.
☁️ Cloud Carbon Footprint: Calculates cloud infrastructure emissions (AWS, Azure, GCP) based on power usage and carbon intensity.
🌍 AWS Customer Carbon Footprint Tool: Tracks the emissions from your AWS workloads and shows how they change over time as AWS increases renewable energy.

These tools allow you to measure everything from API-level efficiency to full cloud workloads, often integrating into CI/CD pipelines or performance dashboards. My personal favorite is Ecograder. It provides a simple, visual way to evaluate how sustainable a website is. The tool analyzes factors like page weight, UX design and green hosting and then gives an overall impact score along with an estimate of CO₂ emissions per page load.

Screenshot Ecograder

Continuous Monitoring

Sustainability is not a one-time task, it’s an ongoing feedback loop. Regularly track SCI and energy metrics to understand how:

Code changes
Infrastructure shifts
Deployment patterns …affect carbon emissions. Even simple actions, like scheduling heavy tasks when renewable energy is abundant, can reduce emissions significantly.

By combining standardized metrics (SCI, GHG Protocol) with modern tools (Kepler, Cloud Carbon Footprint), developers can make sustainability measurable, repeatable and actionable, turning carbon reduction into a core part of software development.

Challenges & Trade-Offs

Balancing sustainability with business goals can be difficult. Green optimizations often conflict with deadlines or existing infrastructure. But in many cases, greener code also means faster and cheaper code. Legacy systems, in particular, lack transparency in energy usage and can require enormous effort to understand and improve. The key is gradual progress: focus on high-impact areas and aim for measurable improvements rather than perfection.

Why It Matters

It’s easy to underestimate how much difference a few lines of code can make. When millions of users interact with your software, even minor optimizations can add up to enormous environmental savings. One striking example from Danny van Kooten showed how removing a 20 kB JavaScript dependency from a WordPress plugin used on over two million websites led to an estimated reduction of 59,000 kg CO₂ per month.

That illustrates how small, focused changes in code and architecture can produce tangible global impact. Writing efficient, sustainable code isn’t just good for the planet, it’s good engineering. Green coding naturally encourages cleaner architectures, less technical debt and faster, more maintainable software.

Conclusion

Here’s your call to action:

Pick one small metric today (e.g., reduce page size by 10%, remove redundant background tasks, schedule heavy workloads for green-energy hours).
Track it, measure it and celebrate the wins.
Share your progress, inspire others in your team or community to join the journey.

Because when developers treat efficiency as part of the craft, sustainability becomes a feature, not an after-thought.
Let’s build code that runs beautifully and gently on the planet. Make yours green and make it matter.