Building Measurement Standards for Indoor Photovoltaics

Indoor photovoltaics is rapidly transitioning from promising research to a dependable energy source for low-power devices. In indoor applications, this allows PV cells to power wireless electronics such as sensors, smart labels, and other IoT devices with nothing but ambient light. 

But as the field accelerates, a key challenge remains; there is still no widely adopted, standard approach to test and report indoor PV performance. This lack of a baseline affects whether results from different labs can be compared fairly, if progress reflects genuine improvements or just artifacts of test setup, and to what extent product teams and customers can trust various performance claims. 

In a recent Joule article, a large group of researchers and industry voices, including Epishine co-founder and R&D Director Thomas Österberg, PhD, make a clear call: the indoor PV community needs consensus testing conditions and clearer reporting practices. 

Why Indoor PV Testing is Harder Than “Just Use a Lamp” 

Outdoor solar has long benefited from standardized reference conditions, such as AM1.5, that enable fair comparisons even if they do not capture every real-world detail. Indoors, light conditions vary widely with the source and setup (spectrum, color temperature, intensity, and geometry), which makes results difficult to interpret and compare without common reference methods. Improving realism in testing is important, but first we need a shared baseline. 

The lack of standardized indoor testing approaches is a key reason results often fail to translate cleanly between both research groups and commercial solutions, making it harder to benchmark technologies and track genuine improvements. 

Consensus Enables Trust, Speed, and Better Products 

Standardized or harmonized testing doesn’t mean “one lamp forever.” It means agreeing on a baseline set of conditions and reporting practices that allows the community to compare devices fairly and understand how performance shifts across realistic indoor scenarios. 

At Epishine, indoor energy harvesting is where our technology is built to perform. As a company with products developed specifically for indoor use, we care deeply about real-world performance, not just best-case lab setups.  

At Epishine, we test the quality and performance of each individual cell according to IEC TS 62607-7-2, the IEC technical specification for evaluating photovoltaics under indoor lighting, to ensure consistent measurements and reliable results. At the same time, as the Joule authors note, this is an important first step—but indoor PV still needs stronger, shared reference conditions and clearer reporting to make results truly comparable across labs and products. Better benchmarking is what turns promising performance into trusted specifications, and Thomas’s contribution in Joule is part of that broader push to help the industry speak the same technical language.  

Epishine’s Roll-to-roll power conversion efficiency tester 

How we are building Measurement Standards for Indoor Photovoltaics 

To get truly comparable indoor PV results, we believe the next step is moving from harmonization toward a clearly defined indoor PV test standard—developed jointly by manufacturers, universities, and end users. Epishine aims to contribute by sharing high-volume test learnings and supporting common reference methods with transparent reporting.  

And because real-world conditions will always vary, we encourage customers to validate performance in their own setup using the same reproducible light and measurement conditions, using the IEC standard as the baseline. 

With rapid sample delivery, we can assess not only power output but also manufacturing readiness by confirming that performance is repeatable across many cells and over multiple production runs.