Christian M. 7 min read

Solar PV batteries | An expert guide

Solar PV batteries are transforming how businesses use solar energy. By storing surplus power generated by your solar PV system, these batteries make clean energy available even when the sun isn’t shining.

They can cut reliance on the national grid, lower business energy bills, and even maximise income through schemes such as the Smart Export Guarantee (SEG).

With the right setup, a PV battery system can also store cheap off-peak electricity to use during peak-rate periods, reducing operational costs and improving the return on your solar investment.

In this guide, our experts explain everything you need to know about solar PV battery systems.

What is a solar PV battery?

A solar PV battery is a large rechargeable battery that stores the electricity generated by commercial solar photovoltaic panels. Instead of distributing unused energy straight to the grid, it stores it so you can use it later when solar generation can’t meet on-site demand, for example, at night or on cloudy days.

The battery connects to your building’s electrical system, allowing it to automatically charge when there’s extra solar power and discharge when needed. It includes an inverter, which changes the electricity from DC (direct current) produced by your panels into AC (alternating current) used by your appliances.

How solar PV batteries work

A solar battery maximises the self-consumption of power produced by solar panels. Here’s how it works in practice:

Step 1: Charging from solar panels

During the day, your solar photovoltaic panels produce direct current (DC) electricity. Any surplus electricity that cannot be used immediately on-site is sent to the battery instead of being exported to the local grid, via a business energy connection

Step 2: Converting and storing energy

The battery charges using the surplus electricity from your solar panels, storing the electrical energy.. This stored energy acts as a reserve, ready to be drawn on later when your panels are no longer generating enough electricity.

Step 3: Discharging as AC when needed

When on-site energy use is higher than your solar generation, the battery releases DC electricity through the inverter, which converts it into alternating current (AC) to provide a direct alternative to your grid connection.

Step 4: Smart energy management

An energy management system (EMS) controls this process automatically. It can also charge the battery from the grid during cheap off-peak periods as part of electricity arbitrage, then discharge during expensive peak hours to lower your business’s electricity bills.

Solar PV battery lifespan, cycle life and warranties

Battery lifespan is a key factor when planning a PV battery system and ensuring you choose a durable option. Solar PV batteries are designed to last many years, but their lifespan depends on how they are used.

Cycle life

Battery lifespan is measured in charge and discharge cycles. Each cycle is one full charge and discharge.

LFP (lithium iron phosphate) batteries: Achieve 5,000 to 10,000 cycles, which can mean 15–20 years of use.
NMC (nickel manganese cobalt) batteries Offer 3,000 to 5,000 cycles, providing approximately 10–15 years of use.

Depth of discharge (DoD)

Depth of discharge (DoD) is the percentage of a battery’s full capacity that can be released in a charge and discharge cycle, while maintaining the lifespan of the battery.

Manufacturers specify a maximum recommended DoD to balance usable capacity with longevity:

LFP batteries can usually be discharged to 90–100%.
NMC batteries are often limited to 80–90%.

Calendar ageing

Even if rarely used, all batteries slowly lose capacity over time. This is called calendar ageing and is affected by temperatures and how full the battery stays.

Keeping the battery cool and avoiding leaving it fully charged for long periods can help reduce this.

Warranties

Most solar PV batteries come with warranties based on years and expected cycles. Typical market warranties are:

LFP batteries: 10–15 years or around 6,000–10,000 cycles
NMC batteries: 10 years or around 3,000–5,000 cycles

Warranties normally guarantee that the battery will retain around 70–80% of its original capacity at the end of the warranty period.

LFP vs NMC: Which is best for businesses?

Modern solar PV batteries are almost always either LFP (LiFePO₄) or NMC (nickel manganese cobalt lithium-ion). Both are proven technologies, but they behave quite differently.

Here’s how LFP and NMC batteries differ across their main characteristics.

Safety and stability

Safety is a top concern in any battery system, especially on business sites where equipment runs daily.

LFP batteries are much more thermally stable and very unlikely to catch fire, even when damaged.
NMC batteries are more energy-dense but more prone to overheating if poorly managed.

For sites with strict safety requirements (schools, care facilities, office blocks), LFP is the safer choice.

Energy density and space

Physical size and weight can be important if space is tight or you’re wall-mounting batteries.

LFP batteries are larger and heavier, but this is rarely a problem in fixed building installations.
NMC batteries are more compact and lighter for the same storage capacity, which is useful where space is limited.

For small sites with limited space or wall-mounting constraints, NMC can be more practical.

Temperature behaviour

Battery performance can drop in hot environments or with heavy daily cycling, so temperature resilience matters.

LFP batteries cope well with high temperatures and frequent cycling, which suits heavy daily use.
NMC batteries are more sensitive to heat and need well-controlled conditions.

For high-use systems that cycle daily (such as commercial premises with solar-plus-storage for peak shaving), LFP offers the best long-term durability.

In summary, LFP batteries generally last longer than NMC batteries and maintain their performance better under daily cycling and warmer conditions. While NMC offers higher energy density in a smaller size, LFP provides greater safety and durability, making it the longer-lasting choice for most solar PV battery systems.

What to look for in solar PV batteries

Choosing the right solar PV battery is about finding the best match for your business energy consumption, building setup and future plans. Here are the key things to check before buying.

Energy capacity (kWh)

The energy capacity tells you how much electricity a battery can store.

Business battery systems typically range from 10 to 100+ kWh, with modular components that can be chosen to suit specific site requirements.
A good approach is to choose a battery that can store roughly half to a full day’s average solar generation.
Consider how your usage might grow, especially if you plan to add electric vehicle charging, or switch to electric process equipment or heating.

Find out more in our guide to what size solar battery you need.

Power rating (kW)

Power rating is how much electricity a battery can release at once.

A higher power rating is essential for running high-demand equipment such as machinery, refrigeration, compressors, or using the battery as a backup emergency power supply.
Lower power ratings are fine if you mainly want to cover lighting, IT and background loads.

New fit or retrofit (AC/DC coupling)

How the battery connects to your PV system affects performance and cost:

DC-coupled batteries connect directly to the solar panels and are best for new installations.
AC-coupled batteries connect to your main circuits and are ideal for retrofitting to existing solar systems.

Check if your current inverter and panels are compatible, and ask your installer whether an additional battery inverter will be needed.

Installer and manufacturer reputation

Battery systems need to be installed correctly to work safely and efficiently.

Choose an installer accredited under the Microgeneration Certification Scheme (MCS).
Look for strong reviews and proven experience with business-scale PV and battery installs.
Opt for established battery brands with good UK support and clear warranty terms.

Physical size and installation space

Solar PV batteries vary in physical size and weight.

LFP batteries are bulkier than NMC models of the same capacity.
Large battery banks may need dedicated plant rooms or floor space.
Ensure there’s enough space for safe ventilation, cable runs and maintenance access.

Checking this early avoids costly redesigns or delays during installation.

Using solar PV batteries with SEG

The Smart Export Guarantee (SEG) is a government scheme that pays businesses for any surplus solar electricity they export back to the grid. Most licensed business energy suppliers offer SEG tariffs, and payments are made per kilowatt hour (kWh) exported.

How SEG works with batteries

When your solar PV system generates more electricity than your business is using, the surplus can either charge your battery for later use or be exported to the grid for SEG payments.

If your battery becomes full, any extra solar electricity will automatically be exported. Some energy suppliers will only pay SEG on power that is exported directly from your solar panels, not energy that has been stored in a battery and then discharged back to the grid.

Battery impact on SEG earnings

SEG export rates are always lower than the price you pay to import electricity from the grid. Adding a battery lets you store solar energy to use on-site instead, which reduces your electricity bills and increases the overall financial return from your system.

Because more of your solar energy will be used on-site, you’ll export less and your SEG earnings will be lower, but the savings on your bills are usually far greater. To get the best value:

Look for SEG tariffs that pay higher rates during peak periods.
Use an energy management system (EMS) to prioritise self-use when business electricity prices are high and export only genuine surplus.
Choose a system size where your battery regularly fills while still leaving some surplus to export if that’s part of your strategy.