What is the difference between residential and commercial solar panels?

Key takeaways

• The panels themselves are broadly the same technology. The differences between residential and commercial solar lie in system size, electrical configuration, grid connection rules, planning requirements, VAT treatment and funding options.

  
  

• Residential systems typically run from 3kWp to 10kWp, using single-phase inverters and G98 grid notification. Commercial systems start from around 20kWp and almost always require three-phase inverters and G99 pre-approval from the DNO.

  
  

• Residential installations qualify for 0% VAT until 31 March 2027. Commercial installations are charged at 20% VAT, reclaimable by VAT-registered businesses

  
  

• Commercial solar is funded differently: outright purchase qualifies for the Annual Investment Allowance (AIA), meanwhile zero-capex Power Purchase Agreements (PPAs) are widely available. Neither AIA or PPA applies to residential.

  
  

• The commercial system design process is more complex: it involves half-hourly consumption data, roof structural surveys, G99 applications, and sometimes planning permission. Getting these stages right determines whether the ultimate financial return matches the modelled projection.

The panels on a factory roof and the panels on a house three streets away are made by the same manufacturers, use the same photovoltaic technology, and look nearly identical from the road. That is where the similarity ends. The two types of installation are designed for fundamentally different purposes, operate under different regulatory frameworks, and are bought, funded and managed in entirely different ways.

For a business owner or property director trying to understand what commercial solar actually involves, the residential frame of reference is sometimes more confusing than helpful. The questions are different, the process is different and the decision-making involves people and considerations that a homeowner never needs to think about.

This article sets out the differences, without assuming any prior knowledge of solar.

Are commercial solar panels actually different from residential ones?

The short answer is: not as much as you might expect. Both types use monocrystalline silicon photovoltaic cells to convert sunlight into direct current electricity. Both are tested and certified to the same international standards. The underlying physics is identical.

Where they differ is in specification and format. Standard residential panels in the UK in 2026 measure approximately 1.72m x 1.13m, weigh 20 to 23kg each, and are rated at 425 to 460 watts. Commercial installations often use slightly larger panels, around 2.0m x 1.1m, rated at 500 to 600 watts, weighing 24 to 28kg. These larger formats are rarely used on domestic roofs because the dimensions are harder to fit on pitched residential roof spaces. On flat commercial roofs and warehouse structures, the larger format can be laid out more efficiently.

Aesthetics matter more in residential installations. Black frames and black backsheets are now standard for homes. Commercial panels more commonly use silver frames and white backsheets, which cost less. For a warehouse covering 5,000 square metres of roof, nobody is typically choosing panels based on how they look from the street.

Panel efficiency, measured as the percentage of sunlight converted to electricity, sits at 21% to 23% for mainstream Tier-1 products. from manufacturers including SolarEdge, Huawei, SMA, Sungrow, and LONGi. This range applies to both residential and commercial panel products from the same manufacturers. Higher-efficiency formats exist for space-constrained applications, but efficiency is not the primary selection criterion for most commercial rooftop projects where roof area is ample.

The right question to ask

When a business asks 'are commercial solar panels different?', what they usually want to know is whether the overall system is different. It is. The panels are a commodity. The system design, electrical infrastructure, grid connection process and funding structure are where commercial solar diverges from residential. The rest of this article covers this.

How does system size differ between residential and commercial?

System size is the most visible difference. A typical UK residential installation in 2026 is 4.6kWp, according to MCS data. It powers the household's lighting, appliances, and increasingly an EV charger or heat pump. A typical commercial installation starts at 20kWp and frequently runs to 100kWp, 250kWp or even larger than 1MW for larger manufacturers, logistics facilities, and cold storage operations.

That difference in scale cascades through almost every other aspect of the project. A 4kWp residential system uses 9 or 10 panels, a single-phase inverter, and a straightforward electrical connection. A 250kWp commercial system uses 500 or more panels, multiple three-phase string inverters or a central inverter, dedicated protection equipment, metering arrangements and a grid connection that requires formal approval from the Distribution Network Operator (DNO) before a single panel can be installed.

Commercial systems are also designed around a specific consumption profile rather than a generic household load. A bakery running ovens from 4am, a cold storage facility running compressors 24 hours a day and a distribution warehouse with peak demand during lorry unloading at 7am all have different energy patterns. The commercial solar system is sized to match that specific profile, maximising the proportion of generated electricity consumed on-site rather than exported cheaply to the grid.

	Residential	Commercial
Typical system size	3kWp to 10kWp	20kWp to 1MW+
Number of panels	7 to 22	40 to 2,000+
Inverter type	Single-phase string inverter	Three-phase string, central or hybrid inverter
Supply voltage	230V single-phase	400V three-phase
Grid connection	G98 notify after install	G99 pre-approval required
Roof type	Pitched, usually concrete or clay tile	Flat or low-pitch, metal or membrane
System designer	Installer (often same day survey)	Dedicated design engineer using half-hourly data
Typical installed cost	£6,000 to £14,000	£50,000 to £1m+ depending on scale
Cost per kWp installed	£1,200 to £2,000/kWp	£700 to £1,100/kWp (lower at scale)
Payback period	6 to 10 years	3 to 7 years.

How does the electrical setup differ?

Most UK homes run on a single-phase 230V supply. A residential solar inverter converts DC power from the panels into single-phase AC at 230V and feeds it into the household consumer unit. The inverter is typically wall-mounted next to the fuse board, and the whole electrical installation is straightforward.

Almost all commercial and industrial premises run on a three-phase 400V supply. This allows more power to be carried at lower current, which matters when you are running production machinery, industrial refrigeration, or large HVAC systems. A commercial solar installation must use three-phase inverters that balance generation across all three phases. The protection equipment, cabling, metering, and connection to the site's distribution board are all more involved than a residential installation.

For commercial systems above 250kWp, a central inverter is often used rather than multiple string inverters. Above certain thresholds, the connection may be made at 11kV high voltage rather than the standard low-voltage network, which adds further complexity and cost to the grid connection process.

Battery storage, which is increasingly specified alongside commercial solar, adds another layer. A commercial battery energy storage system (BESS) needs its own inverter and battery management system, integrated with the solar inverter and the site's energy management controls. The combined system must be modelled carefully to ensure it performs as intended across the site's full range of operating conditions.

What is the difference between G98 and G99, and why does it matter?

This is the single most important regulatory difference between residential and commercial solar in the UK and the one that most affects project timelines. The 16 amp per phase threshold is the dividing line.

G98 (notify after install): Applies to systems where the inverter's AC export capacity is 3.68kW or below on single-phase (16A x 230V), or 11kW on three-phase. The installer connects the system, then notifies the DNO within 28 days. No pre-approval is needed. Most residential installations fall under G98.

G99 (pre-approval required): Applies to any system above those thresholds. The installer must submit a formal application to the relevant DNO, including a single-line diagram, inverter type-test certificates, and a Protection Settings Schedule. The DNO has 45 working days to respond. Systems above 250kWp often trigger a full network capacity study, extending the timeline to 16 to 26 weeks. Almost every commercial installation requires G99.

The practical implication: a commercial solar project cannot start on site until DNO approval is granted. A residential installation can typically go ahead within days of agreeing a contract. The G99 process, if managed well, becomes a parallel workstream running alongside system design and roof surveys. Managed poorly, it is the thing that pushes a project from March into July.

This is why experienced commercial solar contractors submit the G99 application as early as possible in the project programme and why the quality of that application matters. An incomplete submission resets the 45-day clock. A pre-application check of the local network capacity map can flag potential constraints before any fees are paid or any commitment is made.

Do commercial solar installations need planning permission?

Residential solar panels installed on a pitched roof generally fall within permitted development rights in England, meaning no planning permission is needed as long as the panels do not project more than 200mm beyond the roof surface and certain other conditions are met.

Commercial solar is more variable. Many rooftop commercial installations also fall within permitted development under the Town and Country Planning (General Permitted Development) Order. However, planning permission is required in certain situations:

Ashburnham Place - Grade ll listed building

• The building is listed, or in a conservation area

  
  

• The system exceeds certain size or height thresholds set by the local planning authority

  
  

• The installation involves ground-mounted panels rather than roof-mounted

  
  

• The local authority has removed permitted development rights through an Article 4 direction.

For large commercial installations on industrial estates or in edge-of-town business parks, the planning position is usually straightforward and permitted development applies. For heritage buildings, town centre premises, or any ground-mounted element, a pre-application discussion with the planning authority is worth having before the project is committed.

Planning permission, like G99, should be treated as a parallel workstream rather than a sequential step. Businesses that investigate planning and G99 at the same time as commissioning a system design avoid the most common timeline pitfalls.

How do VAT and tax treatment differ between residential and commercial solar?

This is one of the clearest practical differences, and one that directly affects the financial comparison between the two.

VAT

Residential: Solar panel installations on UK residential properties qualify for 0% VAT until 31 March 2027. On a typical £8,000 system, this saves approximately £1,600 compared to the standard rate. The 0% relief applies to panels, inverter, battery, mounting hardware, and labour, all under a single supply contract. From 1 April 2027, the rate reverts to 5%.

Commercial: Commercial solar installations are subject to standard rate VAT at 20%. For a VAT-registered business, this is fully reclaimable. The practical effect is a cashflow consideration rather than a permanent cost. For businesses that are not VAT-registered (turnover below £90,000), the 20% VAT is an additional cost that should be factored into financial modelling.

Capital allowances

Residential: Homeowners cannot claim capital allowances on solar panels. There are no business tax reliefs available for residential installations, only the VAT saving and Smart Export Guarantee income.

Commercial: Businesses can claim the Annual Investment Allowance (AIA) on the full cost of a commercial solar installation, up to the £1 million annual limit. At 25% corporation tax, a £200,000 system generates up to £50,000 of tax relief in year one. This significantly improves the financial return relative to the headline payback period, and it is one of the reasons commercial solar payback periods can be considerably shorter than residential.

Business rates

Since April 2023, on-site renewable generation and energy storage in England has been relieved from business rates. This applies to commercial solar installations and means the added rateable value from a solar system does not translate into an increased rates bill. The relief continues in 2026.

How are commercial and residential solar funded differently?

The funding landscape for commercial solar is fundamentally different from residential, and for many businesses it is the element that determines whether a project proceeds.

Residential funding

Homeowners fund solar through savings, personal loans or home improvement finance. There are no direct government grants for residential solar in most circumstances (ECO4 covers qualifying low-income households). The financial case is based on electricity bill savings and Smart Export Guarantee income, with payback typically in 6 to 10 years.

Commercial: outright purchase

Businesses with available capital can purchase the system outright, claiming the Annual Investment Allowance in year one and owning the asset from day one. All electricity savings and export income accrue to the business in full. This is the highest-return model over a 20-year system life but requires upfront capital commitment.

Commercial: Power Purchase Agreement (PPA)

The zero-capex PPA model has no residential equivalent. Under a PPA, a third party (such as Eden Sustainable, through its parent AMPYR Distributed Energy) funds, installs, owns, and maintains the solar system. The business pays nothing upfront. Instead, it buys the electricity generated at a fixed rate per kilowatt-hour, typically 10 to 14p lower than the grid rate. The contract typically runs for 20 to 25 years.

For businesses with limited capital budgets or those that prefer to keep their balance sheet unencumbered, the PPA is an effective route to immediate energy cost reduction..

Commercial: asset finance

Commercial solar can also be funded through asset finance or green loans, with the equipment used as security. This preserves working capital while allowing the business to own the asset and claim the capital allowances. Payback comes from energy savings and the tax relief, with the finance cost offset against those returns.

How does ongoing maintenance differ?

Residential systems require minimal maintenance. Tier-1 panels carry a 25-year performance warranty. The inverter typically has a 5 to 10-year warranty. Most homeowners clean panels once a year and monitor performance through an app. There is no professional maintenance regime.

O&M is covered under a PPA

Commercial systems are managed assets. A commercial solar installation typically operates under a formal Operation and Maintenance (O&M) contract. This covers scheduled inspections, thermal imaging to identify underperforming strings, inverter servicing, data monitoring against expected generation and DNO compliance checks. For a PPA installation, the O&M responsibility sits with the system owner, not the business.

At Eden Sustainable, our O&M team currently manages over 175 live solar assets. That data gives us a practical picture of what degrades or what fails (and at what point in a system's life). Inverters are the most common failure point. String-level monitoring catches underperformance that panel-level inspection would not reveal until a scheduled visit. A warehouse owner with a 300kWp roof array, running unmaintained for three years without monitoring, can lose significant generation and not know it.

Residential versus commercial solar: a full comparison

Residential solar	Commercial solar
Typical system: 3kWp to 10kWp	Typical system: 20kWp to 1MW+
Single-phase 230V supply	Three-phase 400V supply
G98 notify after install (most cases)	G99 pre-approval before install (most cases)
Pitched roof, concrete or clay tile	Flat or low-pitch, metal or membrane roof
Permitted development in most cases	Usually permitted development; exceptions apply
0% VAT until March 2027	20% VAT, reclaimable for VAT-registered businesses
No capital allowances for homeowners	Annual Investment Allowance: up to 100% in year one
Funded by savings or personal finance	Outright purchase, asset finance, or zero-capex PPA
Payback: 6 to 10 years typically	Payback: 3 to 7 years typically
Monitored via app (informal)	Formal O&M contract with data monitoring
Warranty: 25-year panel, 5-10 year for inverter	Warranty: same panel, higher-spec inverter options
Installer designs on site visit	Design engineer uses half-hourly consumption data
No G99, no planning complexity (usually)	G99, O&M, PPA, AIA, structural survey, planning.

What this means in practice for businesses considering solar

The most important practical takeaway is this: commercial solar is not a bigger version of a residential system. It is a different product designed around a different set of requirements, with a different procurement process and a different financial structure.

The businesses that get the most from commercial solar are those that approach it as a business decision rather than a building improvement. That means starting with consumption data, understanding the financial model before committing, getting the G99 process started early, and choosing a contractor who manages the full process rather than one who simply supplies and installs panels.

Over ten years and more than 300 commercial and industrial installations, the pattern we see consistently is straightforward: projects that are well-planned in advance deliver close to modelled returns. Projects where design inputs, G99, planning and structural surveys are treated as afterthoughts do not. The design and preparation phase determines the outcome more than any specification choice.

Frequently asked questions

Can a business use residential solar panels on a commercial building?

Technically, the panels are often the same products. There is nothing preventing a business from specifying residential-format panels on a commercial roof. The difference lies in the system around the panels: the inverter must be three-phase for commercial premises, the grid connection must go through G99 and the electrical design must meet commercial installation standards. The choice of panel format is secondary to getting those fundamentals right.

What size solar system does a commercial building need?

System size should be determined by the site's actual electricity consumption profile, not by roof area alone. A half-hourly meter data download for the past 12 months is the correct starting point. This shows when demand peaks, how it varies across the week and how much generation would be consumed on-site versus exported. A system sized for self-consumption is worth significantly more per kWh generated than one sized primarily for export. An experienced commercial solar contractor will model this before proposing a system size.

Does a commercial solar installation need planning permission?

Most commercial rooftop installations in England fall within permitted development and do not require a planning application. Exceptions apply for listed buildings, conservation areas, ground-mounted installations and properties where the local authority has removed permitted development rights. A pre-application check with the planning authority takes very little time and eliminates uncertainty before the project is committed. Your installer should be able to advise on the planning position as part of the initial site assessment.

Is there a zero-capex commercial solar option?

Yes. Power Purchase Agreements (PPAs) allow businesses to benefit from on-site solar generation with no upfront capital cost. The system is funded, installed, owned, and maintained by a third party. The business pays for the electricity generated at a fixed rate (below the grid rate), generating costs savings from day one. Eden Sustainable offers fully funded zero-capex commercial solar across the UK under PPA arrangements. The rate and contract terms are site-specific and confirmed at the point of proposal.

What happens to a commercial solar PPA if the business moves or the building is sold?

A PPA is attached to the building and the electricity supply, not to the business tenant or owner. If a business moves out of a leased building, the PPA obligations typically remain with the landlord or transfer to the incoming tenant, depending on how the agreement is structured. If the building is sold, the PPA is usually assigned to the new owner as part of the property transaction. These are material considerations in commercial property deals where solar is in place and they should be reviewed by solicitors during any lease renewal or property sale. Eden Sustainable handles the necessary novation and assignment processes as part of managing our PPA portfolio.

Why is commercial solar payback typically faster than residential?

Two reasons. First, businesses consume the majority of their electricity during the day, when solar is generating, meaning self-consumption rates are naturally higher than for a household where the occupants may be out during peak generation hours. Second, the capital allowances available to businesses mean the effective net cost of the system is lower than the headline installation cost. A £200,000 system that attracts £50,000 of tax relief in year one is effectively a £150,000 investment from the outset. The combination of higher self-consumption and lower effective cost produces faster payback than the residential comparison.

Talk to Eden Sustainable about your commercial site

If you are assessing commercial solar for the first time, we can give you a clear picture of what a system would look like for your specific building, the financial model under both purchase and PPA, and the G99 timeline for your local network. No obligation, and no forms to fill in.

Contact us at edensustainable.co.uk or call to speak directly with a member of our commercial team.