What is green hosting? Sustainable web hosting explained
Green hosting aims to reduce the environmental impact of web hosting. Alongside renewable electricity, energy and water efficiency, infrastructure utilisation, waste heat recovery, hardware management and transparent emissions data all play an important role.
Key Takeaways
Green hosting goes beyond renewable electricity. These are the key points for assessing sustainable web hosting:
- Renewable electricity is a key prerequisite, but an inefficient data centre can still consume excessive amounts of energy and require significant quantities of water.
- Seven key criteria help you assess a provider: renewable energy, energy efficiency, cooling and water, waste heat, hardware lifecycle, emissions transparency, and management and monitoring.
- Metrics such as PUE, WUE, ERF and REF make data centres comparable.
- Certifications and environmental labels can help you assess the sustainability of green web hosting services.
- A checklist and three test cases show how to check claims such as ‘100% green electricity’ or ‘climate-neutral hosting’.
Ask, create and research with the European alternative to ChatGPT. Robust security and unlimited chats give you peace of mind.
What exactly is green hosting?
Green hosting refers to web hosting services where providers take systematic steps to reduce the environmental impact of their data centres. Key measures include:
- Using electricity from renewable sources, such as wind, solar and hydropower
- Using energy-efficient servers and data centre infrastructure
- Optimising cooling systems to reduce energy consumption
- Reducing water consumption in cooling and daily operations
- Recovering and reusing waste heat, for example to heat buildings
- Procuring hardware sustainably, extending its lifespan and disposing of it responsibly
Green hosting is therefore a branch of Green IT. While Green IT covers the environmental impact of information and communication technology as a whole, green hosting (also known as green server hosting) focuses on the infrastructure used to run websites, applications and other online services.
The topic is becoming increasingly important. According to the International Energy Agency (IEA), global electricity consumption by data centres rose by 17 per cent in 2025. Data centres specialising in AI saw an even sharper increase of around 50 per cent. The IEA expects global data centre electricity consumption to reach approximately 950 TWh by 2030, almost double the 485 TWh recorded in 2025. Consumption by AI data centres could triple over the same period.
Although more efficient hardware and software reduce the energy required for individual computing tasks, demand for computing power continues to grow, driven by technologies such as generative AI, video generation and AI agents.
Green hosting goes beyond renewable electricity
Electricity from renewable energy sources is a key prerequisite for climate-friendly hosting. However, even when powered by renewable electricity, an inefficient data centre can still consume excessive amounts of energy and require significant quantities of water, hardware and other resources.
The way electricity is purchased also matters. In Ireland, Guarantees of Origin certify that a corresponding amount of electricity has been generated from renewable sources. The Commission for Regulation of Utilities (CRU) explains that these certificates can be traded independently of the physical electricity supply and help prevent renewable energy from being counted more than once.
It is therefore worth taking a closer look for comparison:
- Does a data centre produce renewable electricity itself?
- Are there long-term electricity supply contracts or power purchase agreements (PPAs) in place?
- Are guarantees of origin disclosed transparently?
Information on the origin should always be considered together with key figures on energy efficiency, water consumption, waste heat and emissions.
7 key criteria for sustainable web hosting
You can assess how sustainably a hosting provider operates by looking at several key criteria.
| Criterion | What to look for |
|---|---|
| Renewable energy | Share of renewable electricity, Guarantees of Origin or on-site electricity generation |
| Energy efficiency | Published energy consumption data and measured Power Usage Effectiveness (PUE) |
| Cooling and water | Efficient cooling systems, water consumption data and Water Usage Effectiveness (WUE) |
| Waste heat | Measures to recover and reuse server waste heat, and metrics such as the Energy Reuse Factor (ERF) |
| Hardware lifecycle | Repair, upgrades, reuse and responsible recycling of servers and components |
| Emissions transparency | Verifiable greenhouse gas emissions data and details of the accounting methods used |
| Management and monitoring | Certified energy or environmental management systems, independent audits and regularly published performance metrics |
Efficient cooling plays a special role in green web hosting. Servers convert a large part of the electrical energy they draw into heat. Depending on the location and technical setup, outside air, optimised airflow or liquid cooling can be used, for example. At the same time, the heat from a data centre can be used for buildings, heating networks or industrial processes.
The hardware itself is also part of the environmental balance. The manufacture of servers, storage and network components requires raw materials and energy. Providers can reduce the impact by using components for as long as possible, repairing or upgrading devices, and reusing or properly recycling decommissioned hardware.
How are energy consumption and emissions measured?
For a meaningful comparison, hosting providers should go beyond general environmental commitments and publish measurable performance data. Established data centre metrics include PUE, WUE, ERF and REF.
| Metric | What does it measure? | How to interpret it |
|---|---|---|
| Power Usage Effectiveness (PUE) | Total data centre energy consumption divided by IT energy consumption | The closer the value is to 1.0, the less additional energy the infrastructure requires |
| Water Usage Effectiveness (WUE) | Water consumption relative to IT energy consumption | A lower value indicates less water consumption |
| Energy Reuse Factor (ERF) | Proportion of data centre energy reused outside the facility | A higher value indicates greater energy reuse, for example through waste heat recovery |
| Renewable Energy Factor (REF) | Share of renewable energy in total energy consumption | A higher value indicates a greater proportion of renewable energy |
| Cooling Efficiency Ratio (CER) | Ratio of heat removed to energy consumed by the cooling system | A higher value indicates more efficient cooling |
PUE is one of the most widely used metrics. For example, if a data centre’s IT equipment consumes 9,600 MWh of electricity per year and the entire facility, including cooling and power supply, consumes 12,000 MWh, the PUE is 1.25. This means that for every 1 kWh consumed by the IT equipment, an additional 0.25 kWh is used to power the supporting infrastructure.
Water consumption can also be compared directly. If the example data centre uses 9,600 MWh of IT energy per year and 960 cubic metres of water, this results in a WUE of 0.1 litres per kWh of IT energy. Cooling technology with low power consumption is therefore not automatically the most environmentally friendly solution if it causes high water demand.
For greenhouse gases, providers can indicate not only energy consumption but also CO₂ equivalents (CO₂e). Scope 1 emissions arise, for example, from fuels for emergency generators or refrigerant losses, while Scope 2 covers indirect emissions from purchased energy.
Certificates and legal requirements
Certifications and environmental labels can help you assess the sustainability of green web hosting services. They provide evidence of renewable energy use, environmental management practices and data centre efficiency.
| Certification or evidence | What does it demonstrate? |
|---|---|
| Guarantees of Origin | Verify that a corresponding amount of electricity has been generated from renewable sources |
| ISO 50001 | Certifies an energy management system focused on continuously improving energy performance |
| ISO 14001 | Certifies a systematic approach to environmental management |
| EMAS | EU environmental management and audit scheme requiring verified environmental reporting |
In Ireland, data centres are subject to EU requirements on energy efficiency and sustainability reporting. Under the EU Energy Efficiency Directive and Delegated Regulation (EU) 2024/1364, data centres with an installed IT power demand of at least 500 kW must report key performance indicators, including energy consumption, water use and renewable energy use, to a European database each year. These figures are used to calculate metrics such as PUE, WUE, ERF and REF.
Ireland also has specific rules for new data centre connections to the electricity grid. Under the Commission for Regulation of Utilities (CRU) connection policy, new data centres must meet at least 80 per cent of their annual electricity demand through additional renewable electricity generation in Ireland, with a six-year transition period. They must also provide suitable electricity generation or storage capacity to support grid stability.
The European Commission presented a common EU rating scheme for data centres in September 2026, with the first labels expected in 2027. It is also preparing a legislative proposal on minimum performance standards.
Checklist for comparing hosting providers
When choosing a green hosting provider, the following questions can help you assess its environmental credentials:
✓ Can the provider demonstrate that its electricity comes from renewable sources?
✓ Are Guarantees of Origin or on-site renewable electricity generation transparently documented and independently verifiable?
✓ Does the provider publish a measured PUE value and specify the reporting year?
✓ Does the provider provide information on water consumption or WUE?
✓ Is waste heat from the data centre recovered and reused?
✓ Does the provider publish its Scope 1 and Scope 2 emissions and explain how they are calculated?
✓ How long is hardware used, and how is it handled at the end of its lifespan?
✓ Are the provider’s energy or environmental management systems independently certified?
✓ Do its sustainability claims also cover outsourced or colocation data centres?
✓ Are sustainability reports and performance metrics regularly updated and publicly available?
Test case 1: ‘100% green electricity’
A hosting provider advertises that it operates its data centres with 100 per cent renewable energy. First, check whether the provider explains how the electricity is procured. Guarantees of origin prove the allocation of renewable electricity volumes, but on their own say little about the energy efficiency of the data centre. The information becomes more meaningful if PUE values, electricity consumption and, where applicable, the provider’s own generation plants or long-term power purchase agreements are also documented.
Test case 2: Low PUE value
Two providers publish a PUE of 1.25. This does not automatically mean that both data centres operate equally sustainably. Also check the reference year, the measurement method and the location, as well as key figures on water consumption. A low PUE can, for example, be achieved with a cooling technology that requires comparatively large amounts of water.
Test case 3: ‘Climate-neutral hosting’
A provider describes its hosting as climate-neutral but does not publish any emissions data of its own. Check whether Scope 1 and Scope 2 emissions are reported and which accounting method the claim is based on. It should also be clear whether emissions are actually reduced or merely offset through climate protection projects. Without such information, the claim can only be compared to a limited extent.
Green hosting in practice at IONOS
IONOS protects the environment, among other things by operating its own data centres with 100 per cent electricity from renewable energies for many years. The 2025 Sustainability Report shows a weighted PUE of 1.37 for the data centres. The energy and environmental management systems in accordance with ISO 50001 and ISO 14001 fully cover the company’s own data centres.
Water and resource efficiency are also recorded using specific key figures. For 2025, IONOS reports a WUE of 0.00003 litres per kWh. In addition, 93 per cent of waste from the data centres was recycled or reused. Three of the nine in-house data centres also generated photovoltaic power on site in 2025 and together produced 2.8 GWh of renewable energy.
Frequently asked questions about green hosting
Does hosting with 100 per cent green electricity automatically count as green hosting?
No. Renewable electricity is an essential criterion, but on its own it is not enough for a comprehensive sustainability assessment of green hosting. Energy efficiency, cooling, water consumption, waste heat recovery, hardware lifespan and transparent emissions data are also essential to sustainable web hosting.
What is a good PUE value?
As a general rule, the closer the PUE is to 1.0, the lower the additional energy consumption for cooling, power supply and other infrastructure. However, there is no universal threshold value that applies to every data centre. Location, utilisation, age and measurement method must be taken into account when making comparisons.
Is shared hosting more sustainable than having your own server?
Shared hosting can make better use of existing hardware because several customers share one physical server. This can reduce the resource requirements per application. However, whether the overall offering is more sustainable also depends on the data centre’s electricity source, efficiency, cooling and hardware management.
Can a website itself become more sustainable?
Yes. Green hosting is only one part of a website’s environmental footprint. Fewer data transfers, optimised images, efficient code and a lean technical architecture also reduce resource consumption. These approaches are grouped under the terms green web design and green coding.