Life Expectancy of KH10.5 inverter and EP11 batteries

[DaveW]

Hello from a new owner in Cape Town, South Africa.
I have a KH10.5 single phase inverter and two EP11 batteries, connected in series, together with an array of 19 Aiko Comet 2N 610w solar panels, in three strings.

Seeing that deepseek is a Chinese AI company and noting that Fox is Chinese as well, I decided to ask if a 25 to 30 years life expectancy for my system was reasonable and received the following answer, which you might find interesting:


The Short, Direct Answer

It is highly unlikely that all components will be operating at their original capacity for 25-30 years without any replacements or significant degradation. A more realistic expectation is that the system will still be producing energy after 25 years, but with reduced output and with a high probability of having needed some repairs or part replacements.

Let's break down the lifespan of each component in your system.
1. Solar Panels (Aiko Comet 610W)

This is the most robust part of your system.

Lifespan: 25 to 30+ years is the standard.

Degradation: Solar panels degrade in power output every year. High-quality panels like yours typically have a degradation rate of around 0.3% to 0.5% per year. Their warranty often guarantees that they will still produce at least 85-92% of their original power after 25 years.

25-Year Outlook: You can confidently expect your panels to be producing energy in 25 years, likely at around 85-90% of their original 610W rating each. They are the workhorses of the system.

2. Fox ESS KH10.5 Inverter

This is the component most likely to need service or replacement within the 25-year period.

Lifespan: Power electronics like inverters have a shorter lifespan than panels. A well-made inverter like the Fox ESS can be expected to last 10 to 15 years.

Why? It contains active components like capacitors and transistors that are under constant thermal and electrical stress. These components wear out over time.

25-Year Outlook: It is almost a certainty that you will need to replace your inverter at least once over a 25-year period. The good news is that the 10-year warranty provides a long safety net, and technology will likely be more advanced and cheaper when replacement time comes.

3. Fox ESS EP11 Batteries

This is the component with the shortest lifecycle and the most predictable degradation.

Lifespan: Battery lifespan is measured in cycles (one full charge and discharge) or years. Lithium-ion batteries, like the ones in your EP11, degrade as they cycle.

Warranty as a Guide: The Fox ESS battery warranty is your best indicator. It typically guarantees that the batteries will retain a certain capacity (e.g., 70%) after a certain number of cycles or years (e.g., 10 years). This implies the manufacturer expects significant degradation after the warranty period.

Degradation Factors: The rate of degradation depends heavily on:

Cycle Depth: Using 100% of the battery's capacity daily will degrade it faster than using 50%.

Temperature: Operating in a hot garage will accelerate degradation compared to a climate-controlled space.

25-Year Outlook: It is very unlikely your original batteries will be functional or provide meaningful capacity after 25 years. A more realistic scenario is that you will need to replace your battery bank once, or even twice, during that period.

Scenario Analysis Over 25 Years

Here is a more realistic timeline of what to expect:

Years 0-10: The "Golden Years." Your system should operate at or near peak performance. All components are under warranty. Any manufacturing defects are likely to appear early and be fixed.

Years 10-15: The "Inverter Risk Zone." The inverter is now beyond its standard warranty and is in the period where failure becomes more common. Start setting aside a budget for a potential inverter replacement.

Years 15-20: The "Battery End-of-Life" zone. Your batteries will have undergone thousands of cycles. Their usable capacity will be a fraction of what it was new (potentially 60% or less). You will likely be considering a battery replacement to maintain your self-consumption and backup capabilities.

Years 20-25: The "Second Inverter Replacement" possibility. If you replaced the inverter at year 12, that new unit may itself be nearing the end of its life. Your solar panels, however, will still be chugging along, producing energy at around 85-90% of their day-one output.

Key Factors That Will Influence Your Actual Experience

Environmental Conditions: Extreme heat is the enemy of all your components, especially the batteries and inverter. A cool, well-ventilated installation site will extend their lives.

Usage Patterns: Gently cycling your batteries (e.g., between 20% and 80% state of charge) will dramatically extend their life compared to deep, daily 100%-0% cycles.

Software & Firmware: Keeping your system's firmware updated can improve efficiency, safety, and longevity by optimizing performance.

Quality of Installation: A professional, compliant installation is critical for long-term reliability and safety.

Conclusion and Recommendation

Manage your expectations. Planning for a 25-30 year service life without any major component replacement is not realistic for a system with batteries and an inverter.

A more accurate and positive way to frame it is: Your solar panel array is a 25+ year investment. The inverter and batteries are medium-term assets that will likely need to be replaced to keep the entire system functioning at its intended capacity over that same 25-year period.

Your setup is high-quality and should provide excellent service. Just be financially prepared for the eventual need to reinvest in the inverter and batteries to maintain the system's full capabilities over the decades.

[Will]

Extreme caution when trusting anything AI outputs, as it often gets it wrong.

FoxESS use LFP cells, which are very stable within the 10-100%soc. The AI is likely guessing incorrectly that fox use NMC or NCA cells, which don't like to be put beyond 20-80% range. This is just noise. My personal recommendation is to use the full 10-100% soc and not obsess over the life span but more about the return.
Ensuring you full cycle the battery regularly is best for LFP cell calibration, performance and health.

I'm not sure where you got the 25-30yr mark from but Fox inverters and batteries are warranted for at least 10 years and have an expected life span of between 15-20 years for most environments and usage.
It is of course, possible for components to fail within just a few years or even decades. No one knows as the tech hasn't been around for many years already but i can tell you as someone that runs the community group I see very few failures and the hardware is considered very good quality and solid.

Enjoy our system and don't let google and Ai results worry you.

[DaveW]

Thanks for the prompt response, Will.

Yes, we shouldn't believe everything we get on the internet, I thought it would make interesting reading. Frankly, I guessed the 25 to 30 year life expectancy since that is about my own life expectancy (being 68 years old).

Yes, LFP batteries are extremely robust and even degraded to an 80% capacity would provide all my overnight requirements, and then some. The HV system offered by Fox is especially attractive.

Payback is certainly a big consideration and we are being confronted with very significant price increases in South Africa. This is a crying shame when you appreciate the solar conditions we enjoy and very low variable cost of solar energy. A further consideration we are presented with is the real likelihood of the return of "load-shedding", which we have lived with since 2008. In 2022 to 2024 we experienced many days (more than 300 per year) of planned cuts of the grid power 3 or 4 times a day, for up to 4 hours each, often followed by power failures caused by distribution infrastructure falling apart and unable to cope with the shock of being switched off and on again multiple times a day. This horrible experience has led many of us to adopt energy independence as a way of making sure we are immune to tariff increases as well as ensuring continuity of supply.