Your power bill arrives, and it’s higher than last quarter again. While commercial solar installations lower electricity costs, picking the right size is necessary to achieve peak efficiency. There is no one-size-fits-all solution for every business.
Knowing your building’s energy needs on peak demand helps you choose a system that works and pays you back. This guide explains how to determine the optimal solar power size for maximum energy savings.
Key Takeaways
- Work out your daily energy load to match the right commercial PV system size.
- Choose an inverter that matches your total power needs, adding 25–30% extra for stand-alone systems or up to three times more for motors and compressors.
- A good solar setup uses deep-cycle batteries for backup power and a charge controller to prevent overcharging.
Analyzing Your Building’s Power Consumption
Knowing your building’s actual energy use is important before planning a commercial solar system. Aim to match the system to your daily energy consumption so you don’t waste money by sending excess solar energy back to the grid for small returns. Consider the average minimum daytime load over a week to determine the panel size.
Start by listing each appliance or machinery, then work out how many Watt-hours it uses daily. Add these up for your total daily demand. To cover system losses, multiply that total by 1.3. For example:
- Appliance use: (18W × 4 hrs) + (60W × 2 hrs) + (75W × 12 hrs) = 1,092 Wh/day
- Total energy needed from panels: 1,092 Wh/day × 1.3 = 1,419.6 Wh/day
A guide to match annual costs with system size:
| Annual Energy Costs | Suggested System Size | Approx. Panels | Expected Annual Savings |
| $300,000+ | 300 kW | 600 | $74,000 |
| $200,000+ | 200 kW | 400 | $50,000 |
| $100,000+ | 100 kW | 200 | $25,000 |
| $50,000+ | 50 kW | 100 | $13,000 |
Get the right commercial solar size for your building and see the savings add up. Speak to a MAG Solar representative for your custom plan.
Other Factors in Sizing Commercial Solar Panel Installations
While total energy demand is an essential consideration, several other technical factors also influence the determination of the right system configuration. Below, we break down how to size the main components of a solar setup to ensure your system operates reliably under varying conditions.
Sizing the PV Modules
To size PV modules for your solar energy systems, you need to find out how much peak power the panels must produce. This depends on your site’s climate, which affects the panel generation factor.
For example, using 3.43 as the panel generation factor:
- Divide your daily Watt-hours by this number to get the total Watt-peak needed. For 1,419.6 Wh/day, this means about 413.9 Wp.
- Then, divide by the panel’s rated output. Using 110 Wp panels gives 3.76, rounded up to four panels for stable performance and better battery protection.
Inverter Sizing
The right inverter size keeps your solar system running safely and smoothly. The inverter must handle the total Watts your appliances and machinery draw at one time. Its input should never be less than this total, and the voltage must match your battery bank.
For stand-alone systems, pick an inverter about 25% to 30% larger than your total machine load. If your system runs motors or compressors, size the inverter three times higher to handle starting surges. For example, with a 153 W load, plan for an inverter rated around 190 W or more.
Battery Sizing
A good solar setup includes battery storage systems to keep your commercial building supplied when the sun isn’t shining. Deep-cycle batteries are the best fit because they handle repeated charging and discharging for years. The goal is to store enough energy to cover night use or cloudy days.
To size your batteries correctly for better energy storage:
- Find the total Watt-hours per day for all appliances/equipment.
- Divide that number by 0.85 to account for battery loss.
- Divide again by 0.6 for a safe depth of discharge.
- Divide by the battery’s nominal voltage.
- Multiply by days of autonomy needed.
Sizing of Charge Controllers
A charge controller protects your batteries from overcharging and keeps the system stable. Picking the right one depends on your PV array’s current and voltage. Match the controller’s voltage to your panels and batteries to keep energy flow steady and safe.
How to size a charge controller:
- Check the short circuit current (Isc) of the PV array.
- Multiply Isc by 1.3 to get a safe margin.
- Pick a controller that can handle this current comfortably.
Common Sizes for Commercial PV Systems
Commercial PV systems generally fall into four sizing categories:
Under 30 kW | Smallest range for commercial setups and is handled by residential installers. This size can produce about 120 kWh of energy per day. |
Between 30 kW and 100 kW | Mid-sized setups commonly used for medium-sized offices, clubs, and retail stores. Unlike smaller systems under 30 kW, these require a commercial solar expert and extra network-approved components. |
Over 100 kW | For large office blocks, mid-sized factories, and hotels. These larger systems involve additional technical steps. |
Over 250 kW | Projects in this range include large solar farms, major shopping centres, and big manufacturing plants. Most installations in this bracket can reach capacities of 15 MW or more. |
Start your solar project with confidence. Talk to our MAG Solar team today for clear advice and safe installation.
Commercial Solar Installation Options
Now that you know how to work out your solar system size, let’s look at the different types of commercial installations available.
- Roof-Mounted Setup: Safe to install and doesn’t interrupt daily work. However, flat roofs don’t receive the sun well, which can affect the amount of energy they produce.
- Ground-Mounted Systems: Can turn unused land into a useful energy source if your roof won’t work for panels. They’re simple to run and maintain.
- Solar Car Shades: Make smart use of parking areas to power buildings with clean energy and fit carports or garage roofs. These systems work for any car park size. For smaller needs, panels can be mounted on poles.
- Building Integrated: Take it a step further by blending solar panels directly into the structure, such as using them as replacement roofing.
- Power Purchase Agreements (PPAs): Instead of owning and maintaining a system, you just buy the clean energy it produces. Work well for bigger companies focused on sustainability, but without space for large solar setups.
Install the Right Size — Contact a Reliable Solar Company
Picking the right solar system size helps your business cut costs and make the most of every kWh produced. Knowing your energy use, sizing your panels, inverter, batteries, and charge controllers all produce long-term savings.
A trusted solar energy contractor can guide you through each step and handle the installation process safely. For a smooth setup, reach out to MAG Solar and get the best fit for your building today.
