The number of panels a commercial solar power grid requires is based on several factors, one of which is the property’s average energy consumption. According to an energy end-use study by the Building Research Association of New Zealand (BRANZ), daily electricity use among commercial buildings ranges between 7.1 and 1,500 kWh per property on average.

Increasing solar energy output can be done in multiple ways, such as installing panels with higher maximum wattage. Although this approach has worked for some establishments, it doesn’t necessarily mean it’ll work for yours. This deep delve into the subject will examine how feasible it is to prefer higher-wattage panels over standard wattage solar panels.

What is Wattage in a Solar Panel?

Solar panel output is displayed in watts, more precisely kilowatt-hours (kWh). This value shows how much power an individual solar panel can produce in a given time under ideal conditions. By ‘ideal,’ experts mean the following:

• Orientation: North-facing panels catch more rays
• Tilt Angle: Depending on the location and season
• Weather: Clear skies can generate more solar energy
• Time of Day: Peak sun hours can yield more solar energy
• Temperature: Excess heat degrades a panel’s efficiency
• Panel Lifespan: Panels lose their efficiency over time

Achieving optimal energy production requires balancing the system's wattage, panel placement, and local conditions. As of this writing, the highest wattage solar panels available can generate up to 500 watts. Under ideal conditions, they can produce and convert an estimated 2 kWh of solar energy daily or more than 700 kWh annually into usable electricity. Of course, the actual wattage output depends on the current conditions.

To put this simply, 2 kWh translates to the amount of electricity a 1,000-watt appliance or equipment uses after running for two hours. Alternatively, it’s the amount of electricity two 1,000-watt appliances or equipment use after running for an hour.

A commercial property in, say, Wellington may pay NZD$0.31 per kWh (as of 2024). When you power your business with commercial solar panels in NZ, using the same amount of stored solar energy saves you just as much per kWh.

What Counts as ‘Better?’

Higher wattage panels are clearly better in terms of producing solar power than lower watt panels, but this isn’t what you want to know. As a business or commercial property owner, your definition of “better” boils down to cost-effectiveness. As such, let’s rephrase the question: “Do higher-wattage solar panels give more bang for your buck?”  

One key advantage of higher-wattage panels is that they’re space-savers. A 500-watt panel can produce as much energy as two 250-watt or five 100-watt panels. Additionally, having fewer panels means fewer panels to maintain or repair.

However, this doesn’t factor in a couple of things. To better understand this, let’s crunch some numbers. Here’s a look into the typical composition and estimated cost of solar PV systems in markets across the country.  

Data source: My Solar Quotes

*Prices include GST but shouldn’t be treated as actual cost of your solar needs, which depends on a slew of factors (e.g., type of PV panel, market location, overall efficiency)
**Calculated by multiplying the estimated system cost by 32% (average proportion of system cost) and dividing the result by the number of PV panels in the system.

A key factor is the price per watt peak or the cost of generating solar power relative to the system’s maximum output. As you can see, the price per watt peak drops as the system output grows. However, it isn’t as clear-cut when compared with the panel output.

Sometimes, increasing the wattage can be more economical; other times, it can be more expensive. While more panels require more space, you can work around this with proper planning and the help of a professional installer. Minding the price per watt peak can go a long way in maintaining a reasonable ROI, perhaps improving it.

How Much Wattage Do I Need, Then?

Generating solar power is only half the equation for an efficient solar panel system. The other half involves using up the stored solar power to fuel your commercial operations. Selling it to energy retailers isn’t an efficient way of breaking even on your solar generation investment, as most of them buy it at cents per watt.

As we just established, bigger doesn’t necessarily mean better. Offsetting a portion of your energy consumption is a good start, whereas becoming almost or entirely reliant on solar is a goal worth striving towards. Beyond the latter, you’ll see diminishing returns.

In other words, if your mom-and-pop shop consumes 5 kW daily, starting with a 2 kW PV system is a good idea. Unless you have the capital to match solar generation with your energy consumption almost one-to-one, you don’t need to invest in a 5 kW system right away. That said, some changes in renewable energy consumption habits are in order.

Conclusion

Choosing the right solar panel wattage ensures that your system efficiently meets your energy requirements while avoiding unnecessary expenses. Higher-wattage solar panels are better if they can satisfy your property’s energy needs for the lowest possible cost. Otherwise, you’re better off with their lower wattage counterparts. Wattage in general should be the least of your concerns when looking for an efficient solar power system; others like price per watt peak are more important.