Consequences of Inaccurate SoE + How to Check It

Battery energy storage systems (BESS) rely on accurate State of Energy (SoE) estimates to operate reliably and profitably. But SoE estimates aren’t always right. Due to system variability and other uncertainties, SoE can swing too high or too low. Either way, BESS asset operators miss out on optimal performance and financial returns.

Here's a closer look at what SoE accuracy means for your entire BESS site, plus three methods to check SoE accuracy: 

Consequences of inaccurate SoE 

Without accurate SoE estimates, your entire BESS operations can become unreliable, jeopardizing not only system performance but your revenue potential and ultimate profitability. This is true whether your SoE estimates are over- or understated. 

Here’s what happens when your SoE estimates are inaccurate: 

• Overstated energy signals lead to inefficient dispatch adjustments, ultimately resulting in underperformance—and associated financial penalties.
• Understated energy signals cause BESS assets to be underutilized, leading to missed revenue opportunities—and a profit hit.

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More ways to grow BESS profit? Discover how shrinking SoC margins can increase your revenue capacity. 

3 methods to check SoE accuracy

Not sure if your SoE estimates are accurate? Here are three ways to assess them: 

1. Ask your vendor: To correctly evaluate SoE accuracy, they should be able to furnish specific data, including average over- and under-predictions and worst-case over- and under-predictions. 
2. Calculate it yourself: If you have access to the necessary data, you can evaluate SoE accuracy yourself. This method gives you direct insight but requires time, effort, and technical expertise. 
3. Get a done-for-you performance analysis from Zitara: Get a deep-dive analysis of your assets’ performance and SoE accuracy, plus actionable information on where to make improvements. 

How to calculate SoE accuracy yourself

With site reliability and profitability on the line, ensuring SoE estimate accuracy should be a top priority for BESS asset operators. 

To determine whether your BESS is giving you accurate information about your site's SoE, follow these three steps: 

1. Check discharge where you know the asset reached a limit

Once a BESS asset reaches its limit, it can no longer provide power, i.e., its remaining power should be zero. 

If your asset has reached this point but its SoE reading isn’t zero, then you know something is amiss. 

Most likely, there is a separate over-prediction and observability issue. But bottom line, you can’t rely on this asset to reliably operate all the way to zero. 

2. Look at what happened before the discharge

After confirming SoE accuracy at the endpoint, it’s time to look backward. 

Check various points before the discharge, whether that’s just a few minutes or several hours beforehand. This way, you can assess whether or not SoE leading up to the discharge was also accurate.

3. Compare forecasted SoE to actual SoE

Finally, compare the SoE forecasted by your EMS with the actual SoE, i.e., what was reported by the revenue-grade meter. 

Make comparisons for each point leading up to the discharge. With this information, you can determine how accurate your SoE is over time—and whether or not you can rely on it to make operational decisions. 

Can you rely on your BESS? Find out why your BESS isn’t always reliable for operational decision-making. 

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Don’t forget to track SoE over time

To better understand whether or not your SoE is accurate (and reliable for operational decision-making), be sure to continuously track overpredictions and underpredictions. Over time, you can develop a clear picture of your assets’ SoE signal accuracy. 

SoE accuracy health check: what it means for your entire site

Use this table for an at-a-glance look at how your SoE impacts total site operations and financial performance.

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A look at site performance with SoE over- or underestimates: 

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A look at site performance with accurate SoE: 

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What if you don’t have the data to assess SoE accuracy?

To correctly assess SoE accuracy, you need access to specific data: 

• Average overprediction 
• Average underprediction
• Worst-case overprediction
• Worst-case underprediction 

If you don't have access to this information—and your vendor can’t give it to you—then it’ll be difficult to effectively evaluate your site’s performance, make confident operational decisions, and maximize profitability. 

Instead of struggling through manual calculations or waiting on your vendor to furnish the necessary data, you can get a done-for-you performance analysis with a Zitara Insight Report. 

Find out your SoE accuracy—and how it’s impacting your revenue

Zitara offers best-in-class SoE estimates to safely maximize your assets’ capabilities for reliable, optimized performance. To back it up, Zitara rigorously validates its performance, reporting average, 95th percentile, and worst-case over- and under-predictions with real historical data. 

With a Zitara Insights Report, you get a deep-dive analysis of your asset’s real-world performance, giving you actionable data to diagnose issues and work confidently with your vendors and integrators to implement solutions to maximize revenue opportunities. 

Check if your SoE is accurate and how to course-correct with your Zitara Insights Report.