Choosing a home battery system can be a daunting task, with numerous options boasting varying features and capabilities. This detailed comparison dives deep into two leading contenders: the Fox ESS Evo and the Tesla Powerwall 3. Both systems utilize cutting-edge Lithium Iron Phosphate (LFP) battery technology, promising long lifespans and reliable performance. However, significant differences exist in capacity, scalability, inverter technology, app functionality, thermal management, and warranty offerings. This analysis meticulously examines each aspect, providing a clear understanding of the strengths and weaknesses of each system to help you make an informed decision.This head-to-head comparison explores key factors like energy capacity and usable power, system expandability, inverter technology and limitations, app features and user experience, thermal management strategies, safety features, warranty coverage, and pricing. We delve into the specifics of each system's performance, highlighting crucial differences in features and potential long-term implications, such as Tesla's Virtual Power Plant (VPP) program. By the end of this comparison, you'll have the information needed to determine which home battery system best aligns with your energy needs and budget.
Pros And Cons
- Around 15 kWh capacity with 13.5 kWh usable capacity (10% margin)
- Expandable up to four units, plus expansion packs (up to 216 kWh total)
- 11.04 kW hybrid inverter with three MPPPTs (up to 20 kW DC solar input)
- Inverter can be downrated in software
- Industry-leading active thermal management system (heating and cooling)
- Stormwatch feature for pre-charging during severe weather
- Tesla app with real-time updates, integrates with other Tesla devices
- Access to Tesla's API for third-party monitoring
- Time of use and self-consumption operating modes
- IP67 weather rating (flood resistant up to 600 mm)
- Dolly included for easier installation
- 80% capacity retention after 10 years with unlimited cycles
- Virtual Power Plant (VPP) participation for potential earnings
- More expensive than Fox Evo
- Requires Tesla Gateway for full house power cut protection
- 10.24 kWh battery system with 9.728 kWh usable capacity (95% depth of discharge)
- Expandable up to three units (29.184 kWh total)
- Integrated hybrid inverter managing solar and battery
- Inverter sizes available: 5 kW, 8 kW, 10 kW
- Up to 300% solar PV oversizing (5kW model), up to 200% oversizing (8kW and 10kW models)
- Charges and discharges at its inverter rating
- Load startup capability (up to 20 kW for 10 seconds)
- Online monitoring portal
- Fox Forest program for carbon offsetting
- API for third-party monitoring and control
- IP66 weather rating
- Small LCD screen for offline monitoring
- 12-year warranty (10 years if not registered)
- 70% capacity retention after 12 years
- Inverter needs to be replaced to increase capacity if DNO restricts power
- Limited expandability if DNO restricts inverter capacity to 8kW or less
- App updates every 5 minutes
- Heat packs for thermal management, not as advanced as Tesla's system
- No dolly included for installation initially
- Requires separate singlephase backup box for full house power cut protection
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Capacity and Expandability
The Fox ESS Evo 10 boasts a 10.24 kWh capacity with 9.728 kWh usable, leaving a 5% margin for longevity. The Tesla Powerwall 3 offers approximately 15 kWh total capacity, providing 13.5 kWh usable capacity with a 10% safety margin. Both utilize LFP technology.
Expandability is another key factor. The Fox ESS Evo system allows for up to three units (29.18 kWh total) on a single supply. The Tesla Powerwall 3 system, however, can be scaled significantly larger, accommodating up to four Powerwall 3 units plus expansion packs (potentially up to 216 kWh total).
This difference in scalability could be crucial depending on your energy needs and available space. While the Fox system offers flexibility, Tesla's capacity far exceeds its competitors.
Inverter and Charge/Discharge Rates
The Tesla Powerwall 3 features an 11.04 kW hybrid inverter with three MPPTs, accepting up to 20 kW of DC solar input. Software allows for downrating to comply with grid restrictions.
The Fox Evo offers three models with different inverter sizes (5 kW, 8 kW, and 10 kW). This modular approach offers flexibility but can lead to capacity limitations if initial DNO restrictions are stringent. Upgrading later requires replacing the entire unit.
In terms of charging and discharging, both systems perform at their respective inverter ratings. This provides efficient and fast charge/discharge times, though the Powerwall 3's software-based downrating provides adaptability that the Fox Evo lacks.
App and Monitoring Features
The Fox Evo uses the Fox Cloud 2 app, providing an overview of system performance, including energy generation, battery state, and grid interaction. It offers historical data graphs and allows for tariff customization and discharge scheduling.
The Tesla app offers real-time monitoring of solar, battery, grid, and EV charging. It allows for off-grid operation and features like Stormwatch for proactive charging before severe weather. The app is more comprehensive and user-friendly.
Both systems offer API access for third-party integrations, offering advanced monitoring options to tech-savvy users. However, Tesla's app has the edge for comprehensive monitoring, user-friendliness and real-time data.
Thermal Management and Safety Features
The Fox Evo uses heat packs to maintain optimal cell temperature in cold conditions. However, this system is reactive, engaging only when temperatures fall below 5°C.
The Tesla Powerwall 3 employs an active thermal management system with fan-forced convection, proactively heating or cooling cells to maintain optimal performance regardless of external temperature.
Both systems incorporate safety features, with the Fox Evo including a thermal aerosol fire suppression system. While this is a positive, replacement of the battery is required after activation. Tesla's system offers advanced thermal management for consistent performance across varying temperature ranges.
Unique Features, Dimensions and Warranty
Tesla's Stormwatch proactively charges the battery before severe weather for backup power. Fox ESS offers a small LCD screen for offline monitoring.
Both systems are similarly sized, but the Fox Evo is shorter. Tesla provides a dolly for easier handling; Fox's dolly is planned for the future. Both have high IP ratings for outdoor installation, although Tesla's offers better flood resistance.
Warranty is another key differentiator. Tesla offers an 80% capacity retention after 10 years with unlimited cycles. Fox provides a 12-year warranty (10 years without registration) with 70% capacity retention after 12 years.
Pricing and VPP
The Tesla Powerwall 3 costs roughly £537 per kWh installed. The Fox Evo 10 kW is around £580 per kWh, the 8kW is approximately £550 per kWh, and the 5kW approximately £520 per kWh. Pricing for the Fox backup box is not yet available.
Tesla Electric and its VPP program are key differentiators. While not yet available in the UK, it offers the potential for additional revenue by supporting the grid during peak demand. This provides a potential long-term benefit for Tesla users.
Although the initial cost per kWh is lower for Fox than Tesla, the absence of a readily available VPP scheme in the UK should be weighed against this. Tesla's VPP offers the potential for additional income and grid support. The final decision depends on individual needs and priorities.
Conclusion
Both the Fox ESS Evo and Tesla Powerwall 3 are strong contenders in the home battery market, each with strengths and weaknesses. The Tesla Powerwall 3 excels in its active thermal management, comprehensive app, Stormwatch feature, and the potential for VPP revenue (when available in the UK).
The Fox ESS Evo offers a competitive price point, especially the 5kW model, and the 12-year warranty provides peace of mind. However, the less flexible inverter sizing and the reactive thermal management system are notable drawbacks.
Ultimately, the best choice depends on individual priorities. If comprehensive monitoring, advanced thermal management, and the potential for VPP income are paramount, the Tesla Powerwall 3 is the preferred option. If cost is the primary concern and flexibility isn't a huge issue, the Fox ESS Evo, particularly the 5kW model, is a worthy consideration.