Can You Add a Battery to Plug-In Solar?

One of the most common questions I’ve been asked since publishing my £300 plug-in solar setup is simple:

“Can you add a battery?”

It’s a great question — because on the surface, plug-in solar systems and battery storage don’t naturally go together. Most plug-in systems are designed to feed power straight into your home, not store it for later.

But as with most things in the home energy space… there’s always a workaround.

So in my latest video, I decided to test exactly that.

The Setup: Hoymiles + EcoFlow

For this experiment, I combined two completely separate systems:

• A Hoymiles microinverter (from the plug-in solar setup)

• An EcoFlow Stream Ultra battery system

Now, these aren’t designed to work together. There’s no official integration, no supported setup, and no documentation telling you to do this.

But the EcoFlow system has a very unusual feature — one I’ll admit I didn’t fully appreciate until I actually read the instructions…

👉 The UK plug sockets can be used for input as well as output.

That means, in theory, you can feed AC power into the battery — not just take power out of it.

Which raises the obvious question:

If the Hoymiles inverter outputs AC… can it charge the EcoFlow battery?

The Result: Yes… It Works

Once everything was connected, the results were pretty clear.

• The Hoymiles app showed solar generation

• The EcoFlow app showed incoming AC power

• The battery started charging

So technically speaking…

👉 Yes — you can add a battery to plug-in solar.

And not in some theoretical way — it genuinely works in the real world.

But There’s a Catch…

Just because something works doesn’t mean it’s the best way to do it.

And this is where things get interesting.

To make this setup work, the energy goes through multiple conversion stages:

1. Solar panels generate DC power

2. The Hoymiles inverter converts it to AC

3. The EcoFlow system converts it back to DC to store in the battery

4. Then later converts it back to AC to power your home

Every one of those steps introduces losses.

Without access to detailed internal data from both systems, it’s not possible to measure this precisely — but realistically, you’re looking at meaningful efficiency losses across the full cycle.

When Does This Make Sense?

This is where context matters.

If you’re trying to build the most efficient, permanent home battery system — this probably isn’t it.

But there are scenarios where it makes sense:

• You’ve got excess solar in summer that would otherwise be wasted

• You want a portable or temporary setup

• You’re experimenting and learning how these systems work

• You’re not ready to invest in a full fixed installation

In those cases, the inefficiency becomes less important.

Because the alternative isn’t “perfect efficiency” — it’s often wasted energy.

The Bigger Picture

One of the reasons I like setups like this is what they represent.

You don’t need a £10,000–£15,000 system to start understanding solar and battery storage.

With relatively affordable equipment, you can:

• generate your own energy

• experiment with storage

• and start reducing your reliance on the grid

That accessibility is a big deal.

Watch the Full Test

I’ve put the full setup, demo, and explanation into a video — including exactly how it’s connected and what both systems report in real time.

👉 Watch it here: https://youtu.be/Po3UhsF4cqg

If you’ve been considering plug-in solar or wondering how batteries might fit into the picture, this is definitely one worth watching.

And as always — just because you can do something… doesn’t always mean you should.