For a DIY or prosumer build, I would pick the Sunsynk 5kW ECCO. I can buy it through a known UK retail route, I know its 48V battery range, and I can check its price – none of which is a given with the Solis S6 hybrid. I would choose a Solis S6 only where my installer or distributor specifies the exact model and battery combination and stands behind it.
Both are single-phase 5kW hybrid inverter options, but that headline hides the practical difference. Sunsynk’s 5kW ECCO is a defined retail product with published figures. With Solis, the model suffix is the whole game: the S6-EH1P5K is a family, and the wrong suffix can mean a different battery pairing or a different grid listing. That is the one thing to pin down, and I will not keep repeating it below.
What is the short answer?
The sensible answer is not that one brand is always better. Sunsynk is easier for a capable homeowner to research and buy as a complete, known item. Solis can be the right answer when an installer or distributor owns the specification, but I would not treat a family name as proof that every S6 unit has the same approval or battery options.
If you are still deciding between hybrid, string or microinverter equipment, start with my guide to choosing an inverter rather than this page. Here I am assuming you want a single-phase hybrid and are down to these two routes, so the useful question is which one leaves fewer unknowns in your own build.
What is actually being compared?
I am comparing the Sunsynk 5kW ECCO Sunk-5K-SG04LP1 with the Solis S6-EH1P5K family. Both are described as 5kW single-phase hybrid inverters. That does not make them like-for-like purchase decisions: Sunsynk’s model details are published together, while the Solis details depend on which unit in the family you are actually being sold.
| Question | Sunsynk 5kW ECCO Sunk-5K-SG04LP1 | Solis S6-EH1P5K family |
|---|---|---|
| AC rating | 5kW rated. The datasheet also lists 5.5kW maximum AC output. | 5kW family rating, depending on the exact unit. |
| Battery side | 48V low-voltage battery, 40V to 60V, with a 120A battery limit. | Low-voltage battery route; the approved battery depends on the exact unit and its datasheet. |
| UK purchase route | UK retail stock was shown at the time of writing. | Available through UK installer and distributor channels. |
| Monitoring and support decision | UK retail stock was shown at the time of writing. Confirm the retailer’s warranty, commissioning and technical-support route before buying. | Ask the supplying distributor or installer what app, commissioning access and first-line support they provide. |
| G98 or G99 | Check the exact model on the current listing before applying or notifying. | The G98 or G99 listing depends on the exact unit, so check it against the current list. |
| Hardware price | £855 ex VAT, at the time of writing. | Not verified in the current retail search; get the price for the specific unit from the distributor. |
The Sunsynk figures above come from its product datasheet. The price was shown by a UK retailer at the time of writing, not calculated as an installed-system price.
Which is easier to buy and get help with in the UK?
Sunsynk is the easier route if you are sourcing parts yourself. The 5kW ECCO was shown in UK retail stock, and there is an established UK retail and DIY support ecosystem around the product. That matters when a homeowner needs to check a cable, setting, battery protocol or documentation before an installer takes responsibility for the finished work.
That is why my own preference leans to Sunsynk for a DIY-led project. I already know from using the smaller ECCO that the surrounding community is part of the product, not an afterthought. My Sunsynk 3.6 ECCO owner review explains the sort of practical support I mean.
Solis is not unavailable in the UK. The S6 family is available through installer and distributor channels. The difference is that this puts the distributor or installer in the useful position of selecting the precise unit. If that is your route, ask them to put the full model suffix, compatible battery and approval status on the quotation.
If you are comparing what is currently offered rather than selecting from a brochure, use the UK inverter directory as a starting point. Then verify the exact equipment you are actually being quoted. Product families change, and a listing for one suffix does not automatically cover another.
Which battery arrangement is safer to specify?
The Sunsynk case is clearer on the information available: the 5kW ECCO takes a 48V low-voltage battery across 40V to 60V, with a 120A battery limit. Those are useful boundaries to take to a battery supplier. They do not replace checking the battery’s own compatibility instructions before the system is ordered or connected.
With Solis, I would not fill the gaps by guessing. The S6-EH1P5K family is described as a low-voltage battery inverter, but the exact model suffix and its battery compatibility must be confirmed from the relevant datasheet and distributor. Ask for that evidence before you buy the inverter, then confirm that the battery supplier agrees with the pairing.
This is not paperwork for paperwork’s sake. The inverter and battery have to communicate and operate within the limits set for that combination. A vague answer such as “Solis S6 works with low-voltage batteries” is not enough to build from. I would want the full suffix written down, the selected battery named and the compatibility confirmed in writing.
How should I judge the monitoring and app?
I would judge monitoring by who will help when it stops being convenient, rather than by a screen in a sales page. Sunsynk has a familiar DIY ecosystem and retail route around the ECCO. For Solis, ask the distributor or installer exactly what app access, commissioning access and first-line support you receive with the precise unit they are supplying.
That question is especially important if you want to understand how your solar, battery and grid import are behaving after handover. A monitoring app can be useful, but it does not make an uncertain specification safe. The first job is still to establish that the inverter, battery and approval paperwork all describe the same exact product.
What must I confirm for G98 or G99?
For either brand, G98 or G99 is an exact-model check, not a brand check. Before an application or notification, confirm the full inverter suffix against the current listing and make sure it matches the quotation and the unit being fitted.
I would make this a written checkpoint before equipment is ordered. It saves the unpleasant position where an installer has one product code, the distributor has another and the DNO paperwork has a third. For the broader role an inverter plays in a home system, see how a solar inverter works, but do not use a general explanation as evidence that a particular unit is approved.
Is the price comparison meaningful?
The £855 Sunsynk figure is useful because it is a visible hardware price, ex VAT, at the time of writing. It is not an installed-system price and should not be treated as one. VAT treatment, delivery, labour, DNO work, backup equipment and whether an installer will fit customer-supplied hardware can all change the real bill.
For Solis, the honest comparison is that the current retail price was not verified. Confirm the exact S6 model, suffix and price with the distributor rather than substituting a price from a different Solis product. A cheaper-looking inverter is not cheaper if the quote later changes because the selected battery, approval route or installation responsibility changes with it.
I would also avoid assuming that a Sunsynk and a Deye carrying similar-looking names are automatically the same purchase. Deye makes OEM and private-label platforms including Sunsynk, but not every model should be called identical. Firmware support and certification must be checked for the exact unit. My Deye versus Sunsynk comparison covers that distinction in more detail.
Which should you choose?
Choose Sunsynk’s 5kW ECCO when you are building a UK DIY or prosumer system and value a known model, UK retail availability, a published 48V battery range and a visible hardware price. It is the lower-friction choice for someone who wants to research every part before asking a competent installer to complete the work.
Choose Solis when a reputable installer or distributor specifies the exact S6-EH1P5K suffix, confirms the compatible battery and provides the current G98 or G99 evidence. That route can be perfectly sensible, but its value is in the supplier owning the detail. I would not choose Solis from a family name and an unverified price alone.
My practical rule is simple: buy the system you can fully identify. For DIY, that points to Sunsynk here. For an installer-led job with a documented Solis specification, let the installer stand behind the chosen suffix, battery pairing, approval and support route before you sign.
