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The technical stuff

Solar battery storage: the next best step for solar PV

We install for passionate people. Customers who want to save the planet; who want to be self-sufficient.

It’s proven. Every day, over 8,000 UK Solar Plants customers monitor their solar PV systems online. But, not only do they want to know if they’re systems are working, they want to know how they’re working too. How they can get the most out of their solar panels and batteries.

This is why we provide the technical information. Why we leave no question unanswered.

The basics

How does solar battery storage work?

Solar PV will provide you with free, clean energy for use. But, without solar battery storage, you’ll never use all of it. Instead, you’ll export any spare electricity to the National Grid. But, you will be able to earn through the Smart Export Guarantee.

Battery storage will automatically store this extra energy. And when your solar panels aren’t producing, your battery will help power the property.

  1. You will always draw power from your solar panels first
  2. When your panels aren’t producing, you will draw power from your battery
  3. If your battery has no charge left, you will then draw power from the National Grid

You can save up to 100%, day-to-day, on your electricity bills with the right system.

Solar Panel batteries

Lead is dead, long live lithium


Lead-acid battery storage was invented in the 1800s. It was the earliest version of the rechargeable battery and has become the most widely used since. It is an inexpensive option but also very inefficient.

A lead-acid battery has a relatively short lifespan, has a low depth of discharge and typically requires more maintenance.


Lithium-ion became commercially available in the 1990s, led by Sony. Since then, it has become the most popular version of the rechargeable battery. It is used in our smart devices, electric vehicles and in battery storage for our energy.

Lithium-ion batteries have a long lifespan, a high depth of discharge and are very efficient. When used in battery storage, it is more expensive than lead-acid but normally has a better return on investment. Both the public and private sectors are investing heavily in lithium though.

Battery Storage Options

The biggest and best of battery storage

At Solar Plants, we only install lithium-ion battery storage. We are able to source any brand, but our preferred models are currently the sonnenBatterie and the Solax Triple Power battery.


The sonnenBatterie is manufactured in Germany. The capacities available range between 2.5-15 kWh. It has a depth of discharge of 90%, whilst in comparison, a lead-acid battery would normally be around 50%.

The sonnenBatterie is modular. This means you could opt for a smaller capacity now and upgrade the size at a later date.

The battery also has an available output of either 2.5/3.3 kW at any given time. It also has an efficiency of +95% and has a warranty for 10,000 cycles.

Solax Triple Power

The Solax Triple Power battery is manufactured in China. The capacities available range between 4.5/6.3 kWh. However, you can connect multiple units and achieve a maximum of 18.9 kWh. It also has a 90% depth of discharge.

The battery has an available output of up to 6 kW. However, in the UK, you would be limited to drawing a maximum of 3.68 kW. It also has a warranty for 10,000 cycles.

Both battery models can charge from the grid. They also have a back-up feature, in case the National Grid suffers from a power outage.

The data

Simplifying specifications

Solar battery storage is going to play a vital role in the future of our energy. It will help us balance the way we use energy, as we move away from fossil fuels to renewables. It is projected that the capacity of global battery storage will reach 125 GW by 2030.

Renewables provide us with clean free energy, but only in varying outputs. This is why there is so much investment and development in battery storage. Especially as our demand for electricity, through low-carbon heating and electric vehicles, increases.

The better you understand technologies like battery storage, the better prepared you are for the future.


This is how much electricity can be stored in the battery. This is usually measured in kWh.


This figure is the maximum rate that the battery can charge/discharge at any given time.

If your property has multiple appliances, which draw a lot of energy, you will require a solar battery with a higher power. If it doesn’t, this specification may be less important.

If you plan to charge the battery from the National Grid too, a higher power rating would also be important to you. This is because you will have more access to power and the capability to actually charge quicker.

Depth of discharge

A battery needs to retain a certain level of charge to prolong its lifespan. The depth of discharge represents what percentage of the battery’s capacity can be used. This percentage varies from battery to battery.

If you are considering solar battery storage, the higher the percentage, the better.


A charge cycle is a process of charging a rechargeable battery and then discharging it for use. Cycles are usually used to specify a battery’s expected lifespan.

Most solar battery storage manufacturers warrant their batteries on cycles and years. This is normally 10,000 cycles or 10 years.

The manufacturer will also specify what percentage of capacity the battery will retain over the warranted years. This could be 80% of its original capacity over 10 years, for example.

However, most battery storage is designed to last far longer; the sonnenBatterie specifies it is designed to last for 20+ years.

If you’re interested in learning more about solar battery storage specifications, you can read our article Battery storage: breaking down a datasheet. Using a sonnenBatterie datasheet, we explain what each specification means.

The survey

The best bit of research you could do

Contact us

Register your interest in solar battery storage using the contact form via the contact page here. We will get in touch to discuss your enquiry.

Technical survey

Our Energy Adviser will visit the property and make an assessment for battery storage. They will explain how it works and calculate the financial figures involved.


Personalised report

You will be provided with a personalised energy report. We can advise if solar battery storage is a good option for you and detail your expected savings. Look over everything in your own time before making a decision.

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Solarplants Ltd is authorised and regulated by the Financial Conduct Authority under number 738735. We are a credit broker not a lender and have a facility with one lender. Solar Plants is a trading name of Solarplants Ltd.

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