Which solar battery should I choose?

#1 Capacity (kWh) vs power (kW or kVA)

• Capacity tells you how much energy the battery stores.
• Power tells you how fast it delivers that energy.

So, look for a battery with enough capacity and power for typical daily use. If, however, your home relies on short bursts of high power (such as EV chargers, heat pumps or large electric appliances), you’ll need something with higher power.

The best way to calculate what capacity and power you need is via a smart meter or monitoring device. Ask a trusted local solar installer for help if you need it. However, in the meantime, here are a couple of rough ballpark ranges (estimates only):

Standard home, moderate electricity use

• Battery capacity: 8 to 14kWh
• Battery power: 3 to 5kW (or 3 to 5kVA)

This should cover a few basics. For example, a kettle or an oven likely draw about 3kW of power (individually).

Home with an EV, heat pump, or higher electricity use

• Battery capacity: 10 to 30kWh
• Battery power: 5 to 1 kW/kVA

These homes demand a lot more from your electrical system, and if you have the solar array to provide a large amount of charge, it’s worth investing in a top-of-the-range battery. Remember, you can always fall back on the grid.

#2 AC-coupled vs DC-coupled

Solar panels produce DC electricity, but homes and the national grid run on AC electricity. You need an inverter to convert the DC from the panels into AC power for your lights, sockets, appliances, and for exporting to the grid. A battery stores energy as DC, so if it connects on the DC side of the solar inverter, it’s called DC-coupled; if it connects on the AC side (with its own inverter/charger), it’s called AC-coupled.

• AC-coupled batteries connect to the same AC electricity your home already uses. They work well if you’re adding a battery to an existing solar system, because they don’t require changes to your panels or inverter.
• DC-coupled batteries connect before the electricity gets converted for use in your home. They usually come as part of one matched system, with the battery and inverter designed to work together. This setup tends to move energy more efficiently inside the system and is often chosen for new solar installs.

Here’s a quick explainer between the two.

In an AC-coupled battery:

1. Solar panels make DC
2. The solar inverter converts it to AC (so your home can use it)
3. To charge the battery, that AC is converted back to DC
4. When you use the battery later, the DC is converted back to AC again

That’s DC → AC → DC → AC.

Each time the electricity converts between DC and AC, you lose a small amount. However, as mentioned, it’s simpler to install in an existing system.

In a DC-coupled battery:

1. Solar panels make DC
2. The battery stores that DC (without needing to convert it)
3. When you draw from the battery later, the inverter converts DC to AC

That’s DC → AC (only once). Because a DC-coupled battery avoids one extra conversion step in the solar-to-battery-to-home path, you don’t lose as much energy as in an AC-coupled battery. But it’s a more complex setup, and better suited for when you’re installing an entire solar system (panels + battery) at once. This can all feel a little complex. It’s best to chat us for tailored advice.

#3 DNO export limits (often G98/G99)

Most UK homes have a limit on how much power they can export at once. The most common threshold (for straightforward connections under the most common regulation, G98) is 3.68kW per phase. Your battery and inverter should offer settings that align with this. Even if it doesn’t, the DNO export limits still limit your battery’s export performance.

The DNO export limit doesn’t limit the power supply going from your battery into your home, just what goes back into the grid (under most normal conditions). There are still plenty of options even with stringent DNO export limits.

#4 Warranty and ongoing maintenance

Solar battery warranties usually tie to either years, cycles, or the remaining capacity. Although it might not be the most interesting thing in the world, do read the terms and conditions. The last thing you want is to be stranded with a battery that nobody will service, or one that costs far more than similar systems.

Battery systems people choose in the UK

With those four points in your mind, here are a couple of the most common solar battery systems that British homes opt for.

SigEnergy SigenStor

SigEnergy’s SigenStor is the ideal place to start looking. This system treats your entire home as one combined platform to be built over time (if desired). You get the inverter, storage, energy management, and optional extra modules (for more capacity) all in one.

The real benefit with SigenStor is how easy it is to add capacity by ‘stacking’ modules. This is fantastic, as it allows you to start small and build more capacity in as your needs change. You can choose between the 5.0 module (5.38kWh) and the 8.0 module (8.06kWh), then stack up to six in parallel to maximise your capacity. That’s a total potential capacity of 48kWh per stack.

And because it’s all one platform, it means SigEnergy’s app (mySigen) has a comprehensive and in-depth overview of your entire electrical system. You can check your use, battery health, solar generation and export figures all from one place.
Who it’s for: homes investing – or planning to invest in – electrical systems, especially EVs or heat pumps. Also homeowners looking to integrate all solar and electrical demand under one platform.

Tesla Powerwall 3

The Tesla Powerwall 3 is another practical option for British homeowners. It’s a powerful full home setup with one unit and an app to run the monitoring and operating modes. You can connect up to four units in parallel.

And it’s that power that really makes the Powerwall 3 stand out. You’ll get a nominal battery capacity of 13.5kWh, with configurable AC output options up to 11kW (great for powerful home usage, but don’t forget about the DNO export limits). It also comes with a 10-year warranty.

Who it’s for: homes prepared to invest in very high power output (and capacity) from one integrated unit.