Adding a battery to a Solis solar system
For a solar-only Solis system, Solis's own route is its S6-EA1P AC-coupled inverter plus a low-voltage (40–60 V) lithium battery. Solis says it can add storage to any brand of existing solar. Several batteries we cover also say, in general terms, that they can be added to existing solar.
Compatibility by existing system
“General statement” means the battery maker says it can be added to existing solar in general, without naming Solis. Your installer should confirm the details.
| Your existing system | Tesla Powerwall 3 | Enphase IQ Battery 5P | myenergi libbi | Sunsynk L5.1 with ECCO inverter |
|---|---|---|---|---|
| Solis grid-tied (string) inverter, solar only | Works via AC couplinggeneral statementNeeds: Tesla Remote Meter and solar CT (as drawn in Tesla's example); Backup Gateway 2 for backupTesla's UK datasheet shows an existing (AC-coupled) solar inverter alongside Powerwall 3, measured by a Tesla Remote Meter with a solar CT. Not specific to this brand.Source: Tesla datasheet, p.7, Partial Home Backup ... and AC Coupled Solar | Works via AC couplinggeneral statementEnphase's UK planning guide covers retrofitting IQ Battery 5P to an existing string-inverter solar system. General statement, not specific to this brand.Backup: Needs an IQ System Controller 3 INT. In backup, the solar that can stay on is limited to 100% of battery power with a string inverter.Source: Enphase manual, Key considerations: Retrofit; sizing guideline 4 | Works via AC couplinggeneral statementmyenergi says libbi can be added to any existing solar system. General statement, not specific to this brand.Source: myenergi datasheet, p.1–2, Flexible install; use-case table | Works via AC couplinggeneral statementSunsynk says the ECCO hybrid inverter can AC couple to retrofit an existing solar system. General statement, not specific to this brand.Source: Sunsynk datasheet, p.1, features |
| Solis hybrid inverter with a battery already | Not documented | Not documented | Works via AC couplinggeneral statementmyenergi lists "I have solar and a battery already and want to add more storage" as a supported retrofit: libbi goes alongside the existing system. General statement, not specific to this brand.Source: myenergi datasheet, p.1–2, Flexible install; use-case table | Not documented |
Not listed: Sigenergy SigenStor, Fox ESS EVO 10, SolarEdge Home Battery 400V, Huawei LUNA2000-S1. We haven't found manufacturer documentation for adding these to an existing Solis system, so we don't claim they work.
Solis's own option: the S6-EA1P AC-coupled inverter
Solis describes the S6-EA1P as an AC-coupled inverter that adds storage and emergency power to an existing grid-tied solar system, “suitable for any brand”. From its UK datasheet:
| Models (rated output) | 3.6, 4.6, 5 and 6 kW |
|---|---|
| Battery | Lithium-ion, 40–60 V, CAN communication |
| Max battery charge / discharge current | 75 A (3.6K) · 96 A (4.6K) · 105 A (5K) · 125 A (6K) |
| Battery-to-AC efficiency | Over 93.5% (maximum) |
| UK grid standards | G98, G99 |
| Size, weight, rating | 440 × 465 × 192 mm, 19.9 kg, IP66 |
Source: Solis S6-EA1P(3.6-6)K-L UK datasheet (Flyer V2.1) and Solis UK product page. The UK datasheet doesn't list a backup (EPS) output, so ask your installer whether the model you're quoted gives backup.
If you already have a Solis hybrid and battery
Adding more storage to a Solis hybrid depends on Solis's battery-matching list, which we haven't profiled yet. myenergi says libbi can go alongside a system that already has solar and a battery.
How long would it run your home?
Try the runtime calculator, or compare two batteries side by side.
Questions people ask
Can I add a battery to my Solis inverter?
If you have a solar-only Solis inverter, Solis sells the S6-EA1P AC-coupled inverter to add battery storage to an existing system. Solis says it suits any brand of solar. You can also add a battery that has its own inverter, such as myenergi libbi, Enphase IQ Battery 5P, Tesla Powerwall 3 or Sunsynk with an ECCO inverter, which their makers say can go alongside existing solar.
What batteries work with the Solis S6-EA1P?
Solis's UK datasheet lists lithium-ion batteries at 40–60 V with CAN communication. Solis publishes its own battery-matching list; check it with your installer.
Sources
- Enphase Energy System planning guide — single-phase backup systems (UK) — Enphase, TEB-00305-1.0, July 2025. Checked 26 Sept 2026.
- Powerwall 3 Datasheet (UK) — Tesla, 2026. Checked 26 Sept 2026.
- Sunsynk ECCO SUN-3.6/5/6/7.6/8K-SG05LP1-EU datasheet (2022 edition) — Sunsynk. Checked 26 Sept 2026.
- libbi Home Battery datasheet (DS-00001) — myenergi, Revision A, October 2023. Checked 26 Sept 2026.
- S6-EA1P(3.6-6)K-L (Solis UK product page) — Solis. Checked 26 Sept 2026.
- Solis S6-EA1P(3.6-6)K-L AC-Coupled Inverter datasheet (UK) — Solis, UK Flyer V2.1. Checked 26 Sept 2026.
EnergyPicker is independent and not affiliated with Solis. Always confirm your final design with an MCS-certified installer.