Equipment Tax: More gear, more problems

Microinverter systems have been praised for their modularity and simplicity. But as solar systems grow in average capacity and integrate battery storage, that simplicity comes at a cost: more hardware, more maintenance, and more complexity.

This is the third piece of the Microinverter Tax—the cost of excess equipment. Let’s unpack why AC-based systems require more equipment, and why DC-optimized systems offer a cleaner, smarter alternative.

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The Equipment Problem with AC Architecture

Microinverter-based systems paired with AC-coupled batteries require roughly double the inverter capacity compared to DC architectures. Using the same schematics previously used for the conversion losses, AC architecture with microinverters requires 88% more - nearly 2x - the inverter capacity compared to a DC architecture with optimizers (21.4kW vs. 11.4kW)

AC Architecture Inverter Capacity: 21.4kW

1. 11.4kW on the roof +
2. 10kW in the battery

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DC Architecture Inverter Capacity: 11.4kW

1. 11.4kW inverter (for both solar modules + battery)

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Expanding on the difference, AC architecture requires:

• Microinverters: Installed under each module to perform DC-to-AC conversion
• Battery Inverter: A separate inverter to manage AC-coupled energy storage (often integrated into the battery enclosure)
• Additional Components: Combiner boxes and other equipment to connect the systems and try to minimize breaker space it uses at the electrical panel

This configuration means:

• More hardware is required. AC architecture requires inverters for solar and a separate inverter for the battery. Compared to DC architecture where one battery serves both.
• More Points of Failure: Each microinverter on the roof is doing a lot of work and is a potential point of failure. If one does fail years later, a like-for-like replacement is required.
• Difficult Access: Microinverters are mounted on the roof under solar modules, making repairs labor-intensive and costly.

“Fixing or replacing a failed microinverter is more difficult, since you would need to go up to the roof, work the rack, and unbolt the module to access the unit.” - Aurora Solar

One of the owners of Solartime USA, a Texas-based solar plus storage installer that does microinverter and string inverter systems, puts it succinctly based on her experience:

“With more components involved, microinverter systems may require more maintenance and more potential replacements over time. Also… inverter will be located on top of the roof… which can lead to a higher labor cost when fixing.”  - Solartime with Martyna (YouTube)

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How DC architecture simplifies solar + storage

DC-optimized systems, like those using Tigo TS4 optimizers and a hybrid inverter, simplify solar installations by consolidating components. Here’s how:

• One Inverter for Solar and Storage: A hybrid inverter eliminates the need for a separate battery inverter, reducing both costs and complexity.
• DC optimizers perform the module-level optimization, monitoring, and rapid shutdown functions of microinverters but don’t do the extra work of converting energy from DC to AC
• Easier Maintenance: The piece of equipment doing the most work – the inverter – is located at ground level, typically shaded from the elements.

The Bottom Line

Microinverter systems that are paired with batteries require more hardware than DC architecture – that’s the essence of the Equipment Tax. And as we showed in previous sections, the Equipment Tax comes not at a premium to performance, but with losses associated with the Clipping Tax and Conversion Tax.

Our next chapter dives into the preferred technology stack for efficient residential solar - The solution is DC: DC optimizers, DC coupled batteries

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Want more?

Webinar: On April 15 (Tax day in the US), we're hosting a webinar that will dive into the details of the Microinverter Tax series. Sign up for the webinar here.

Below is a full list of chapters included in this series (links will be added as chapters are published):

1. Summary: The Growing Microinverter Tax
2. Trendlines: Major Changes in the Solar Industry
3. Clipping Tax: Leaving energy on the table
4. Conversion Tax: The hidden cost of AC-coupled batteries
5. Equipment Tax: More gear, more problems
6. The solution is DC: DC optimizers, DC coupled batteries
7. Bonus: Clipping showdown: MLPE vs. Optimizers
8. Glossary of terms

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