For a business, net zero means cutting greenhouse gas emissions across everything it is responsible for, not just the electricity bill. That includes fuel burned on site, power bought in, and the emissions in its supply chain and products. Solar helps with the second of those. On its own, it leaves the other two untouched. That gap is the most common reason a net-zero claim falls apart when someone checks it.
Scope 1, 2 and 3 in plain terms
The Greenhouse Gas Protocol is the accounting standard most corporate frameworks use. It sorts emissions into three groups:
- Scope 1 is direct emissions from things you own or control. Think gas boilers, company vehicles, on-site fuel and refrigerant leaks.
- Scope 2 is the emissions behind the electricity, heat or cooling you buy.
- Scope 3 is everything else in the value chain, from the goods you buy to the disposal of what you sell. The protocol sets out 15 categories, both upstream and downstream.
Solar you generate and use on site cuts the power you buy from the grid. That lowers Scope 2. It can also lower Scope 1 where it replaces fuel burned on site, such as a diesel generator. It does nothing directly for Scope 3.
Why Scope 3 usually dominates
For many firms, the supply chain is the biggest part of the footprint. CDP, the environmental disclosure body, found that corporates’ supply chain emissions averaged 26 times their operational emissions, using 2023 reported data. That is an average. It varies a great deal by sector. A cement maker’s direct process emissions weigh heavily. A retailer or professional-services firm looks very different.
So a business can put solar on every roof, fully decarbonise its own energy, and still have dealt with only a small share of its footprint. Scope 3 is harder to act on because it depends on suppliers and customers, not only on your own capital spending. That is why informal net-zero claims often leave it out.
What the Science Based Targets initiative says
The Science Based Targets initiative (SBTi) runs the Corporate Net-Zero Standard, the benchmark most credible corporate claims are tested against. Its long-term aim is net zero by 2050 at the latest.
The standard is in transition. The SBTi site says Version 2.0 is available now, with target validation under it starting in the first quarter of 2027. Version 1.3.1 can still be used for target setting until 31 January 2028. From 1 February 2028, all new submissions must align with Version 2.0. Check the SBTi pages for the detailed criteria before you commit to a target, because they differ between versions.
SBTi validation is not a legal requirement in the UK. However, customers, lenders and investors increasingly ask for it as proof that a target means something.
What the law requires
The UK government is legally bound to a net-zero target. Section 1 of the Climate Change Act 2008 says the net UK carbon account for 2050 must be at least 100% lower than the 1990 baseline. That duty sits with the State. It does not bind individual companies to reach net zero.
Some companies do have reporting duties. Under the Companies (Directors’ Report) and Limited Liability Partnerships (Energy and Carbon Report) Regulations 2018, known as Streamlined Energy and Carbon Reporting (SECR), quoted companies and large companies and LLPs must report on energy and carbon in their annual reports. Who counts as large depends on company size tests, and those tests have been revised in recent years. Ask your auditor or accountant whether you are in scope, rather than relying on a figure from an article. Reporting is about disclosure, not about committing to net zero. Our post on SECR, ESG reporting and solar evidence shows how solar data feeds those reports. For definitions, see our glossary.
Where solar fits
Solar is a strong lever for Scope 2. It is measurable, it sits on your own roof or land, and the data comes from your own meters. That makes it much easier to evidence than a certificate that covers someone else’s generation.
What it is not is a plan for fleet emissions, process heat or the supply chain. A practical order that tends to stand up to scrutiny is:
- Cut demand first, through efficiency, controls and better building fabric.
- Electrify what still burns fossil fuel on site.
- Generate what you can on your own roof or land.
- Work on the value chain through supplier engagement and buying standards.
Solar belongs in step three. It is worth doing on its economics alone, but it is one step in four. For the money side, see how much commercial solar costs in 2026 and whether battery storage is worth it. Sites with heavy process loads should also read about solar for manufacturing process heat and compressed air.
What else a credible plan needs
Alongside on-site generation, a plan that survives questions usually has:
- A full baseline. All three scopes, built to the Greenhouse Gas Protocol, not just an energy bill comparison.
- A reduction path with interim targets. So progress can be checked each year.
- Supplier engagement. Scope 3 cannot be solved by spending on your own estate.
- Disclosure that matches the claim. Statutory reports and any voluntary reports should tell the same story.
- Named actions with owners and dates. A transition plan, not just a pledge.
Worked example (illustrative only)
Suppose a distribution firm measures its footprint and finds that its warehouses account for a tenth of it, mainly electricity. Suppose its fleet and its contracted haulage make up most of the rest. Putting solar on every depot could make a visible dent in Scope 2 and lower its bills. But the biggest items are diesel vehicles and bought-in transport, which solar does not touch. The firm would also need a fleet plan and a supplier programme. The numbers are invented. They show why a baseline should come before a headline.
Where we help
Our net-zero strategy service places on-site generation alongside efficiency, storage, procurement and reporting, so a good energy bill does not stand in for the whole plan. If you want a view of one site first, a feasibility study tests whether solar is worth the capital.
Sources: GHG Protocol, Scope 3 Standard; CDP, supply chain emissions 26 times operational emissions; Science Based Targets initiative, Net-Zero Standard; Climate Change Act 2008, section 1; Companies (Directors’ Report) and LLPs (Energy and Carbon Report) Regulations 2018.
Since solar covers only part of a footprint, put it inside a wider plan. Our net zero strategy work does that, while energy and ROI modelling prices each measure. A feasibility study sizes the array, and portfolio optimisation ranks sites across a group. For reporting rules, see SECR and ESG reporting.