Charge Cheap While You Sleep: Adding Battery Storage to Existing Solar

You already have solar. Now make your energy work harder.

If you installed solar PV a few years ago, you may already know the feeling.

On a bright summer’s day, your panels can generate plenty of electricity. Your home uses what it needs, and the rest is exported.

But then evening arrives. The sun goes down, your solar generation stops and your home starts buying electricity from the grid again.

It’s one of the biggest challenges with solar PV: the sun doesn’t necessarily shine when your home needs the most electricity.

This is where battery storage can change the way you use your solar system. And if you’ve already got an existing solar PV installation, an AC-coupled battery could be the solution you’ve been looking for.

Your Solar Panels Are Already Doing Their Job

If you already have solar PV, you’re halfway there.

Your panels generate electricity during daylight hours, but without a battery, you can only use that electricity immediately or export it. A battery gives you somewhere to put surplus energy until you need it.

So instead of generating electricity at lunchtime and then buying electricity again in the evening, you can store some of that daytime generation and use it when your household demand increases.

But there’s another opportunity that many solar homeowners haven’t considered. Your battery doesn’t have to rely solely on your solar panels.

Charge Cheap While You Sleep

With a suitable time-of-use electricity tariff, an AC-coupled battery can be charged from the grid during a lower-cost period, often overnight.

You go to bed. Your home uses very little electricity. Your battery charges during the cheaper period.

Then, when the household wakes up and electricity demand starts increasing, the stored energy can be available for your home to use. Later in the day, your solar panels can take over again, charging the battery with surplus solar generation when conditions allow.

This creates a much more flexible system. You’re not simply storing solar. You’re managing when your home takes electricity from the grid and when it uses stored energy.

What Is an AC-Coupled Battery?

If you already have solar PV, an AC-coupled battery can be particularly attractive because it can be added to an existing solar installation without necessarily replacing your existing solar inverter.

The battery has its own inverter and connects on the AC side of your electrical system.

That can make it a practical option for homeowners who already have an established PV system and don’t want to start again from scratch. It’s also an important consideration for homeowners who receive Feed-in Tariff payments.

Can I Add Battery Storage and Keep My Feed-in Tariff?

This is a question we hear regularly.

If your existing solar PV system is receiving Feed-in Tariff payments, adding battery storage needs to be approached carefully.

The key issue is ensuring that the electricity generated by your FIT-accredited installation can still be accurately measured and distinguished from electricity coming from other sources, including electricity stored in a battery.

Ofgem’s guidance confirms that battery storage can be co-located with a FIT installation, provided the relevant metering and measurement requirements continue to be met.

For homeowners with existing FIT arrangements, an AC-coupled battery can therefore be an important option to consider, because it can allow the battery to be installed alongside the existing PV system while keeping the FIT generation and export arrangements appropriately separated.

However, FIT arrangements can vary, particularly depending on how your existing system is metered. That’s why this isn’t something to simply add to your system without checking first.

At Solar Select, we can look at your existing installation and FIT arrangement before recommending a battery solution.

What Does an AC-Coupled Battery Cost?

Retrofit battery prices depend on capacity, your existing inverter and how your system is metered, so the only accurate figure comes from a survey. Two things are worth knowing before you ask for one.

First, retrofit and standalone battery storage has qualified for 0% VAT in its own right since February 2024, and that relief is scheduled to end on 31 March 2027. If you are weighing up a battery for an existing solar system, that deadline is worth factoring in.

Second, you don’t have to fund it in one go. You can spread the cost with 0% finance for up to 24 months, subject to status and terms.

What If You Don’t Have Solar Yet?

You don’t have to own solar panels to benefit from battery storage.

A battery can be charged from the grid during cheaper periods and used later, depending on the tariff and system configuration. For some homes, this can provide a way of shifting electricity consumption away from higher-cost periods.

Add solar in the future and the battery can potentially become part of a wider solar and storage system. The important thing is to design the system around how your home actually uses electricity.

It’s Not Just About Summer

Solar and battery storage are often associated with sunny summer days. But a properly considered battery system can have a role throughout the year.

In summer, your battery may spend much of its time storing surplus solar generation. In spring and autumn, it can combine solar charging with cheaper grid charging where appropriate.

And during the darker winter months, when your solar panels may generate less surplus electricity, charging the battery during cheaper periods can help keep the system useful.

Your solar generation changes with the seasons. Your battery strategy can change with it, and so does keeping your system performing at its best.

Think of Your Battery as an Energy Store, Not Just a Solar Accessory

This is the important shift. A battery isn’t simply somewhere to put excess solar. It can become a way of moving electricity from one time of day to another.

• Your solar panels generate when the sun is shining.
• Your battery stores energy.
• Your electricity tariff determines when grid electricity may be cheaper.
• Your home decides when energy is needed.

The battery sits in the middle, helping connect all three. That can make a significant difference to how you use your existing solar PV system.

If you want the basics first, read how solar panels and batteries work together.

Already Have Solar? Let’s Look at What’s Possible

If you have solar panels without a battery, you may be missing an opportunity to make greater use of the electricity your system generates.

If you’re on a Feed-in Tariff, you may have an even more important reason to get the system assessed properly before making changes.

And if you’re considering a battery from scratch, it’s worth looking beyond simply choosing the biggest battery you can fit. The right system depends on your solar generation, household consumption, existing inverter, electricity tariff and, where applicable, your FIT arrangements.

At Solar Select, we look at the whole system rather than treating solar and battery storage as separate products. We’ll assess what you already have, how your home uses electricity and what options are available to you.

Because if you’ve already invested in solar, the next step doesn’t necessarily mean replacing what you’ve got. It could simply mean making it work harder.

• Charge from the sun when it’s available.
• Charge cheaply from the grid when it makes sense.
• Store energy for when you need it.

And make your solar investment work harder, all year round.

Talk to Solar Select about adding battery storage to your existing solar PV system.