RailWatts is reader-supported. If you buy through links on this page we may earn a commission, at no extra cost to you. It never changes what we recommend. How we make money.
- Balcony batteries are mostly an EU/UK product category; US options are still limited.
- For a single 800 W kit, 1.5-2.5 kWh of storage covers most sunny-day surplus.
- Look for LFP chemistry, smart-meter integration, and a clear warranty in years and cycles.
- 2026 launches pushed capacity and solar input much higher, aimed at people who want more than a balcony kit.
This guide compares products on published specs and independent reviews; it is not based on our own lab testing. Availability differs by country, so check before you plan.
In this article
Comparison
| Battery | Capacity | Highlights | Price (2026) | Markets |
|---|---|---|---|---|
| Anker SOLIX Solarbank 2 E1600 Pro | 1.6 kWh | Popular entry model, app, smart-meter support | ~€799 | Europe |
| Anker SOLIX Solarbank 3 E2700 Pro | 2.7 kWh | More capacity and solar input | Higher | Europe |
| EcoFlow STREAM Ultra | 1.92 kWh | Integrated inverter, app, backup outlets | ~$1,279 US listing | EU, UK, US (limited) |
| EcoFlow STREAM Ultra X | 3.84 kWh | 4 MPPTs, 2,300 W backup output, 10-year warranty | £1,499 / ~€1,427 | UK, EU |
| Zendure SolarFlow 2400 Pro (IFA 2026) | Modular | 4,800 W solar input across 4 MPPTs, 2,400 W bi-directional | TBA | EU |
| Anker SOLIX Solarbank Max (IFA 2026) | 7 kWh, expandable to 42 kWh | Up to 10,000 W solar input | TBA | TBA |
Specs and prices from manufacturer announcements and 2026 reviews. Always check current listings.
Best for one 800 W kit: Anker Solarbank 2 E1600 Pro
Enough capacity for typical surplus, a mature app and a lower price than bigger units. Check price
Best for backup and east-west setups: EcoFlow STREAM Ultra X
Four independent solar inputs and strong off-grid outlets make it the most flexible. Check price
For bigger ambitions: Zendure and the new “Max” systems
These go beyond balcony scale: they can take many panels and act as home batteries. Useful if your rules allow more panels behind storage, but they are no longer a small, cheap purchase. See Zendure
In the US
Options are limited; EcoFlow’s PowerStream with a DELTA station has been one route. See power stations with balcony panels and watch for UL-certified plug-in batteries.
What to check before buying
- Chemistry: LFP. Why.
- Coupling: DC or AC. Differences.
- Warranty in years and cycles, and end-of-warranty capacity. Reading the spec sheet.
- Legal status where you live: UK.
- Payback: does storage pay?
How we would choose, step by step
- Measure surplus first. Run your kit for a few sunny weeks and note daily exports. Under 0.5 kWh a day, skip the battery.
- Decide on backup. If you want power during outages, shortlist only batteries with an off-grid outlet.
- Check local rules. Plug-in batteries are not yet clearly covered in the UK, and certified options are limited in the US.
- Size to surplus and evening use: usually 1.5-2.5 kWh for one kit. Sizing guide.
- Compare price per usable kWh, standby consumption and warranty. Spec sheet guide.
- Pick an ecosystem whose app and smart-meter integration you like, since mixing brands rarely works well.
What we’d avoid
- Batteries without clear LFP chemistry or certification.
- Warranties that don’t state end-of-life capacity.
- Oversized systems bought “for the future” when your kit can’t fill them.
Frequently asked questions
Can I use a balcony battery in the US?
Options are limited and certification requirements apply. Watch for UL 3700 and UL 1973/9540 listings on US products.
Do these batteries provide backup?
Some have off-grid outlets (EcoFlow STREAM, for example); others do not. Check before buying if backup matters. Outages.
Which size should I buy?
For one 800 W kit, 1.5-2.5 kWh usable is usually enough. Sizing guide.