When most people think of designing a solar energy system, they imagine all the panels tilted at the perfect angle, facing due south (at least here in the northern hemisphere), soaking up maximum sun. And if you’re trying to squeeze every last kilowatt-hour out of your system for annual production, that’s a textbook approach.
But if you’re designing an off-grid solar energy system, or even a grid-interactive system with battery backup that you want to actually work when the grid goes down, that “perfect” orientation isn’t always the smart choice. Let’s break down why.
Off-Grid Reality: Power When You Need It, Not Just How Much
Off-grid homes don’t care about how much energy you generate over the course of a year—they care about having power when you need it. There’s a big difference between maximum annual production and usable production when the batteries are begging for juice.
If you point all your panels south at the optimal tilt, here’s what happens:
- You get lots of production at midday, especially in summer.
- You risk starving your batteries in the morning and late afternoon.
- You may generate more power than you can store at peak, wasting energy unless you massively oversize your battery bank (which is extremely costly).
By spreading your solar array across different orientations… say, some panels east, some south, some west, you create a more even power curve. That means:
- Your batteries get charged earlier in the day (east-facing panels).
- You extend charging into the late afternoon (west-facing panels).
- You reduce the risk of hitting 100% state of charge and wasting energy at noon, while still struggling to keep the lights on at dawn.
Real World Scenario Where Morning and Afternoon Solar Production is Deficient
Check out this data from an actual off-grid customer’s data monitor. They have only one south-facing solar array. You can see why there would be an advantage of having some of those south facing panels reoriented to the east and west. There is more than ample sun on most days to recharge the batteries, but the generator has to run on some mornings or nights because the household electricity consumption exceeds solar production early and late in the day, meaning the batteries have to carry the load during these periods.
Why It Matters: Living on Batteries
An off-grid home lives and dies by battery performance. You want to:
- Minimize the time your generator runs.
- Keep your batteries in the optimal state of charge range.
- Avoid large swings that reduce battery life.
Diverse panel orientations help smooth out your charging profile, allowing your batteries to stay healthier and your generator to remain silent.
Grid-Interactive with Battery Backup: A Similar Concept
Even in a grid-tied system with battery backup, these ideas can still be applied. Sure, when the grid is up, your south-facing array at optimal tilt will maximize your net-metered production. But when the grid goes down? Suddenly, it’s not about annual output anymore. It’s about survival.
If your panels are all optimized for midday, you could have:
- Frustratingly slow charging in the morning after a night of battery drain.
- Missed opportunities in the late afternoon to top off your batteries before another night.
If you’re willing to sacrifice a few percent of annual production (let’s say 5–10% loss from non-optimal panel orientation), you gain:
- Faster morning recovery after a storm knocks out the grid.
- Longer usable production hours in the afternoon to stretch battery capacity.
In grid-tied systems where full net metering applies, those few percent lost annually are easily outweighed by the real-world resilience you gain when the grid is down. And if your goal is to achieve 100% annual utility offset, you can simply install 5-10% more panels and meet both goals.
The Numbers: A Quick Estimate
Let’s put it in perspective:
- A pure south-facing array at optimal tilt might generate 100% of its theoretical annual output.
- If we install some panels east and west, we might see total annual production drop by 5–10% compared to that perfect south-only array.
- But in return, we can dramatically improve early morning and late afternoon production, sometimes by 20–40% in those hours where power is needed most.
That tradeoff is worth it if your goal is reliable power, not just the biggest net metering credit or annual kWh bragging rights.
How Much Is Too Much?
You might ask, why not just put all panels facing east and west? That could be useful in some scenarios. However, typically, bulk charging at midday is crucial for efficiently recharging depleted batteries.
There is a degree of art in the science of solar design. We can’t predict exactly how people will use power, so we use experience to deal with these challenges. A healthy pre-sale conversation with our clients also leads to better results. For example, if you have a beach house and you and your friends will frequently come off the beach around 4:00 pm, shower, and throw all of the towels in the washing machine, we are probably going to want to beef up the west-facing solar array. We might even want to put more panels facing east, but if you tell us your family likes to sleep in, that might not be important. If the coffee machine doesn’t start up until 9:00 am, there might be enough solar power to cover it.
Of course, in an off-grid system, we usually have a generator for redundancy, but who wants to hear that? Fuel is expensive and hard to deliver if you are on an island. And the biggest problem with generators is that the start/stop logic built into inverter automatic generator start systems today isn’t all that great. For example, you would not want to start the generator with batteries dipping to 20% if it’s 9:00 am and there is a sunny day ahead. But that is a real scenario that causes generators to run when we don’t want them to, or even need them to.
But Wait, Why Not Simply Go Big?
You might ask, why not just over size the battery or solar array. Those are options, but there are significant downsides to consider, aside from the obvious cost impacts.
The “Just Add More Battery” Approach
At first glance, you might think you can solve orientation challenges by simply adding a bigger battery bank. With more storage, you’d catch every watt of midday sun from south-facing panels.
But batteries are by far the most expensive component of an off-grid system. Oversizing them just to compensate for suboptimal panel orientation quickly becomes a costly mistake.
There’s another drawback to a huge battery bank paired with south-only panels: your batteries won’t regularly reach 100% state of charge. Batteries—especially lithium types—need to hit full charge frequently for proper cell balancing.
Without regular full charges, cells can become unbalanced. This results in inaccurate state-of-charge readings and reduced battery longevity.
The “Just Add More PV” Approach
Another common workaround is installing an oversized PV array, all pointed directly south. On paper, flooding your system with abundant solar seems logical.
But going too big with solar can create problems of its own. Routinely charging batteries at very high rates is tough on them, accelerating cell degradation and shortening their usable life.
Sure, modern systems can programmatically limit the charge rate to protect the batteries. But now you’ve introduced another problem: artificially restricting solar input when you might actually need every watt available.
This makes oversizing your PV array—not to mention the extra costs associated with it—another less-than-ideal solution.
Final Thoughts: It’s About Smart Design
The bottom line is this: For off-grid systems (and often for grid-tied systems with battery backup), it’s not about chasing maximum annual production numbers. It’s about creating a system that matches your lifestyle, usage patterns, and survival priorities when the grid is down. That means thinking beyond “optimal tilt and orientation” and looking at the whole picture.
When we design your system, we’re not just aiming for the textbook best-case scenario. We’re building something that actually works for you when it counts. Building some flexibility into the design, or installing systems in phases, can help you save money by learning when you need power, not just how much. This applies to both battery sizing and solar panel sizing and orientation.
PostScript – Southwest Florida Nuances
In Southwest Florida, we don’t design off-grid systems for average conditions — we design for the worst-case scenario. And that worst case typically shows up in September, right at the peak of hurricane season. During this time, the afternoons are often dominated by heavy clouds and storms. Sure, sometimes the sun breaks through after a squall, but you can’t bank on that. What that means in practice is that west-facing panels, which look good on paper for stretching production into the afternoon, can end up delivering very little on the days you actually need them most. When it’s cloudy and stormy by mid-afternoon, those west panels might as well not be there.
That’s why we often bias the array design toward the east. After a long night of battery drain, getting power into the system early is critical. The faster you can recharge those depleted batteries in the morning, the better your chances of avoiding unnecessary generator starts. East-facing panels give you that early boost, helping to stabilize the system before the afternoon clouds roll in.
Of course, sometimes rooflines or property layouts don’t allow for perfect panel orientation. That’s just part of the reality of solar design. In those cases, we work within the site’s limitations and balance what’s ideal with what’s physically possible, always with reliability as the top priority.
