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Commercial solar · Offices

Solar for offices: weekday loads, shared roofs and landlords

An office uses most of its power in daylight on weekdays, which suits solar well. The hard part is usually who owns the roof, and who pays the bills.
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Two-storey office building with rooftop solar and a solar carport

The short answer

  • Weekday daytime use matches solar output, so a well-sized system is mostly used on site.
  • Weekends and holidays send solar to the grid, so size for the weekday load.
  • Rooftop space is limited in a multi-storey building. The roof often serves all tenants.
  • If you are a tenant, the landlord or building owner must agree, and the bill may sit in their name.
  • A battery rarely suits a standard office unless there is an evening or overnight load.

How offices use power

A typical office runs on weekdays from around 8am to 6pm. The main loads are air conditioning, lighting, computers and, in larger buildings, lifts and ventilation. Air conditioning follows the weather: it works hardest on hot afternoons when solar is also at full output, which is a good match.

Outside working hours the load drops to baseload: servers, security, emergency lighting, standby equipment and some ventilation. Weekends are the biggest gap. A system that is sized too big will export most of what it makes on Saturday and Sunday, and exports usually pay little.

Multi-storey buildings have a small roof for the amount of power they use, so solar often covers only a slice of the bill. A low-rise office park, or a standalone building with a flat roof or carpark, has more room.

Typical sizes

Ranges, not recommendations: your bills, roof and network decide the right size.
Up to 100 kW
Small-scale STCs
Most single-tenant offices and small blocks. STCs apply for the years left until 2030 and fall each year.
100 kW to 1 MW
Mid-scale STCs
Larger low-rise buildings and campuses. Installed from 1 October 2026, a fixed 5-year deeming period applies.
30 to 200 kW in Victoria
VEU activity 47
Non-residential premises; check with the accredited person.
Battery
Usually not the first step
A battery makes most sense where there is a night-time load or a tariff reason. NSW and federal discounts exist for businesses.

Is it a good fit?

What tends to make it pay

  • Owner-occupied or long-leased buildings with a flat, unshaded roof.
  • Strong air conditioning and ventilation load on hot days.
  • A low-rise or standalone building where the roof area is large relative to use.
  • Weekday use that makes up most of the annual bill.
  • Rooftop or carpark space that is not already taken by plant.

Sort these out first

  • Tenants usually can’t install without the landlord’s approval, and the landlord may not benefit from the savings. This split incentive stalls many office projects. A written agreement on who pays and who benefits helps.
  • If the building is submetered or part of an embedded network, the savings may not flow the way you expect. Check how you are billed.
  • Weekend export earns little. Size the system for the weekday load.
  • Building services (cooling towers, plant, lift motor rooms) take roof space and cause shade.
  • Roof access, wind loading and fire rules can limit the layout on multi-storey buildings.
  • Large buildings may have a demand charge, and solar may not lower the peak. Model both.
  • Check lease length against the payback period before committing.

Rebates and programs that can apply

Programs change often, so check the official page before you rely on one. Our guide to commercial solar rebates covers every state.

  • Australia

    Federal STCs for systems up to 1 MW

    Systems up to 100 kW get small-scale technology certificates (STCs) for the years left until the scheme ends in 2030. Mid-scale systems (100 kW to 1 MW) installed from 1 October 2026 can claim STCs with a fixed 5-year deeming period; the Clean Energy Regulator said applications would not open until mid to late November 2026. Choosing STCs for a mid-scale system means no REGO certificates during the deeming period.

    Official details

  • Victoria

    Victorian Energy Upgrades: commercial and industrial solar (activity 47)

    An upfront incentive, in Victorian energy efficiency certificates created by an accredited person, for 30 to 200 kW solar at grid-connected non-residential premises. It is not available at apartment buildings. It can sit alongside STCs. Systems above 200 kW are not eligible under this activity.

    Official details

  • NSW

    NSW business battery discount

    From 1 September 2026, non-residential sites in NSW installing a 20 kWh to 30 MWh battery can get an upfront discount in the installer’s quote: indicatively about 30 to 40 per cent with new or additional solar (installed within 90 days either side), or about 20 to 30 per cent for a battery alone. Batteries of 20 to 200 kWh need a minimum payment. Sign the installer’s nomination form before work starts. Data centres and off-grid sites are excluded. It can be combined with the federal programs if you meet both sets of rules.

    Official details

  • Australia

    Cheaper Home Batteries (federal)

    Households and businesses can get STCs for a new battery of 5 to 100 kWh installed with solar of up to 1 MW, but STCs count only the first 50 kWh and taper above 14 kWh. The battery must be on the Clean Energy Council list, installed by an accredited installer with a battery endorsement, and capable of joining a virtual power plant. The per-kWh factor falls in steps: 6.8 until December 2026, then 5.7 from January 2027.

    Official details

  • Australia

    $20,000 instant asset write-off

    From 1 July 2026, small businesses with aggregated turnover under $10 million can deduct the full cost of an eligible asset costing under $20,000 in the year it is first used or installed ready for use. Larger systems can go in the small business pool. This is general information: ask your accountant how it applies to you.

    Official details

A 50 kW system on a weekday office, estimate only

A worked example, so you can see how the numbers fit together. Yours will differ.

Assumptions

  • Monday to Friday, 8am to 6pm, using 80,000 kWh a year, with the calculator’s default 20% running around the clock.
  • Postcode in solar zone 3, installed in November 2026, so 5 years of small-scale STCs at $35 each.
  • Installed price $1,050 per kW before certificates, excluding GST (the calculator’s default for 30 to 100 kW).
  • Grid energy at 25 c/kWh excluding GST, exports at 3 c/kWh, prices rising 2.5% a year, panels declining 0.5% a year, maintenance $12 per kW a year.
  • The building owner agrees and holds the electricity account. No battery, demand charges, finance or tax effects.

What it works out to

  • Output: about 69,100 kWh in year one, with the model expecting about 71% (about 49,300 kWh) used on site.
  • Cost: $52,500 before certificates. About 345 STCs are worth about $12,100 at $35, leaving a net cost of about $40,400.
  • Year-one saving: about $12,900, a simple payback of about 3.3 years. Over 25 years, the model gives an internal rate of return around 32% and a net present value around $129,000 at a 7% discount rate.
  • Roughly 29% of the output is exported at 3 c/kWh. A smaller system would use a bigger share on site but save fewer dollars in total.
Run your own numbers

An estimate from the Solar Retailers commercial solar calculator, not a quote. A tenant who does not pay the power bill, or who does not own the system, will see a different result.

Questions to ask an installer

Ask every installer the same questions so the quotes compare like for like. More in how to choose a commercial solar installer.
  1. Who needs to approve the installation, and have you worked with building owners and managers before?
  2. How much roof is usable once plant, access paths and shade are taken out?
  3. What will happen to the output on weekends, and what is the export price on my plan?
  4. Do I pay for my own power, or is it through a landlord, embedded network or submeter?
  5. Have you checked the roof structure, wind loading and fire access for this building?
  6. Can you show how the design handles a demand charge, if I have one?
  7. What happens to the system if the lease ends or the building is sold?

Guides for this decision

Other types of business

Questions

I rent my office. Can I still get solar?
Possibly, but the landlord must agree. Some landlords install it and recover the cost through the lease or a power purchase arrangement. Get the terms in writing and ask your accountant or lawyer to check them.
Will solar cover my whole bill?
Rarely. In a multi-storey building, roof area limits output, and night-time and weekend use still comes from the grid. Ask for the share of your annual use that the system is expected to supply.
Is a battery useful for an office?
Usually less than for a site with evening loads. If you have a demand charge or a time-of-use tariff, a battery might help, but ask the installer to quantify it.
What if my building has a shared meter?
Then the savings depend on how the power is billed between tenants. Ask your building manager how it works, and have the installer show who benefits.

Sources

Checked 31 October 2026. This page is general information, not financial, tax or legal advice. Rules, rebates and prices change, so check the sources before you decide.

Ready to compare real numbers?

Run your own figures first, then ask at least three accredited installers to quote on the same brief. Quotes are free and you’re under no obligation.

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