By the PPA Funding team Last updated
Your supply type sets how much solar a site can take. Single-phase supplies, common in small units and homes, cap the system size and export. Three-phase supplies, standard on most commercial sites, carry more power and support larger arrays. The supply also shapes the grid connection application and inverter choice.
What is the difference between single and three-phase supply?
A single-phase supply delivers power through one live conductor and is typical of homes, small shops and light commercial units. A three-phase supply uses three live conductors, delivering more power more smoothly, and is standard for factories, warehouses, farms and larger premises with heavier equipment.
You can usually tell by the main fuse and meter: a single large fuse points to single-phase, while three fuses point to three-phase. If you are unsure, an electrician or your feasibility surveyor can confirm before any solar design work begins.
How does the supply affect the size of solar you can fit?
Single-phase connections are limited in how much generation they can take and export, so the array is capped even if the roof could hold more. Three-phase gives more headroom, letting you install a larger system and export more without unbalancing the network.
This is why most sizeable commercial solar sits on three-phase sites. If your roof is large but the supply is single-phase, an upgrade to three-phase may be possible, but it carries a cost and lead time set by the network operator. The feasibility study should flag this early.
What does this mean for connection and inverters?
The supply type feeds directly into the G99 connection application, which sets the limit the network operator will allow. A three-phase array uses three-phase inverters that spread generation evenly across the phases, while a single-phase system uses a single-phase inverter with a lower ceiling. Getting the inverter matched to the supply avoids tripping and wasted generation.
None of this changes the PPA offer itself: under a PPA the funder still covers the equipment and you buy the output at a fixed rate at least 30% below the grid. The supply simply shapes how large the system can be. Your surveyor and the funder handle the technical detail.
This guide is general information, not financial or tax advice. Your circumstances determine what applies — please confirm with your accountant or advisor. Get a tailored proposal →
Frequently asked questions
Is my commercial site likely to be single or three-phase?
Most commercial premises with any real electrical load, such as workshops, warehouses, shops with refrigeration or offices with air conditioning, are three-phase. Very small units may still be single-phase. A quick look at the meter and main fuse, or a call to your electrician, will confirm it.
Can I still get solar on a single-phase supply?
Yes, but the system size and export are capped by the supply. That may be fine for a small roof and modest demand. If you need a larger array, you can ask the network operator about a three-phase upgrade, which adds cost and time. The feasibility study will advise.
Related guides
- Commercial solar and fire safety: how a rooftop PV array is protected against fire
- Does solar work in a power cut? Why grid-tied systems shut down, and what keeps you running
- Solar for multi-let commercial buildings: sharing generation between several tenanted units
See our funding options, commercial solar and solar by industry pages.