Energy storage | Good Finance

An energy storage system allows you to capture heat or electricity when it is readily available, such as from a renewable energy system, storing it for you to use later.

The most common energy storage systems include electric batteries, hot water cylinders and electric storage heaters.

In this guide, we will only talk about battery storage systems.

This page will explore everything you need to know about energy storage to better understand whether it's an energy saving measure that could work for your organsation. Scroll to learn more, or click the button below to download the full guide in PDF format.

Download the guide to Energy Storage

What are the benefits of battery storage?

Electrical batteries can help you make the most of your renewable generation system. For example, electricity generated during the day by solar PV panels could be stored in an electric battery to be used when your panels are no longer generating electricity.

A battery can also be used to store electricity bought from the grid at cheaper times of the day, so you can use it at peaks times when electricity may be more expensive. This can save you money if you are on a variable electricity supply tariff.

Some tariffs also pay you different rates for electricity you export at different times of day, so you can use a battery to wait until the best time to export your surplus generation.

Is battery storage suitable for my building?

If you have, or plan to have, a renewable generation system supplying your premises then you need to consider how much electricity will be generated when, how much you are likely to use when, and how the two match up. If you have a solar installation that generates during the day and you only occupy the building during the day then you may be able to use most of your generated electricity immediately, rather than exporting it, and there may be little benefit in adding battery storage.

However, if your electricity demand peaks at times of the day when generation is likely to be low then you are far more likely to see a financial reward from fitting a battery. It is very difficult to predict generation, use and the value of storage with complete accuracy, but a rough assessment of the likely match between time of generation and time of use can help you decide whether storage is worth investigating further.

Battery characteristics

There are two different battery technologies that can be used for small scale and short term storage of electricity within a building’s energy system...

Lead-acid batteries

These have been used in a range of electricity-storage applications for more than 30 years.

The technology is similar to that used in a petrol or diesel vehicle’s starter battery, but designed specifically for longer term energy storage.

Lead-acid batteries, due to their low cost, are widely used in many larger energy storage applications and especially in applications not connected to the grid where there are no limits on space.

However, you need to replace the batteries several times during the lifetime of a battery storage system.

Lithium-ion batteries

This technology is increasingly becoming more popular and is currently used in many modern, compact small-scale or domestic electricity storage systems because they are lighter and need less space. Lithium-ion batteries are more expensive than lead-acid batteries but due to their longer lifetime (more than 4000 cycles) they do not need to be replaced as often.

The second parameter is the charge or discharge power, quoted in kilowatts. This is the maximum rate at which you should charge or discharge the battery.

The third important parameter is the battery lifetime, quoted either in number of charge/discharge cycles or just in years. Lead-acid battery storage units have a lifetime of around five years on average, depending on how the system is used, while lithium-ion systems generally have a lifetime of 10 years or more.

Energy storage underneath solar panels on roof

What battery size do I need?

Your battery size depends on a number of factors, including budget and space available, but also the amount of timing of your likely generation and likely electricity use, as well as the electricity tariff structure for both importing and exporting.

There are a number of electricity battery systems currently on the market and more are likely to appear in the future. The capacity of typical small (domestic-sized) electricity batteries ranges from 1kWh to 8kWh, enough energy to boil your kettle from 10 to 70 times.

Larger “off-the-shelf” units are available for non-domestic use, or you could buy a ‘stackable’ system where you can add multiple smaller batteries, or you can get a bespoke system design.

Indicative costs and savings

The cost will vary depending on the size and type of battery as well as the practicalities of the installation. Here's some indicative costs...

Will installing a battery save me money?

You are likely to save money from installing a battery alongside a renewable generation system as you will be able to use more of the generated energy to operate your appliances rather than exporting it to the grid.

As you usually pay more to import electricity than you can earn from exporting it, this will reduce your bills. You may be able to increase this saving by choosing a variable tariff and changing when you charge and discharge the battery to take advantage of the varying prices offered.

Carbon savings

Installing a battery will not directly reduce your carbon dioxide emissions as it will not reduce the total amount of electricity you use.

In fact, as some energy is lost in charging and discharging the battery, your total consumption is likely to increase slightly. However, fitting a battery does have significant indirect benefits by enabling the installation of additional renewable generation systems without putting extra strain on the network.

There is currently no appropriate and accepted methodology for quantifying this benefit and so it cannot be used when calculating your carbon footprint, but it is a very real benefit nonetheless.

How long does it take to install commercial battery storage?

The installation time can vary depending on the complexity of the installation and the size of the battery. Typically, for smaller systems, it takes just one day.

Disruption during the installation

No major disruptions are expected during the installation of battery storage systems, apart from disconnection of the electricity supply for a short period.

Can I do this by myself?

Energy storage systems are not a technology that you can install by yourself. You will need to talk to an installer who will assess your needs and evaluate your building before proposing which system could be right for you. Click here to learn more about this.

Energy Storage in Action...

See below for a list of real-life examples of energy storage installations in charities, social enterprises and community organisations across the UK...

Peedie Kirk United Reformed Church

Peedie Kirk United Reformed Church in Kirkwall, Orkney received funding to install solar PV panels and battery storage. The Kirk wanted to use as much of the energy generated by the solar panels as possible and installed battery storage so that they could save excess energy to be used at a different time. The members estimate that they can produce 1750kw each year from a 6kw solar PV system combined with 7.5kwh of battery storage.

Alford and District Men’s Shed (ADMS),

Alford and District Men’s Shed (ADMS), a community building in rural Aberdeenshire, installed a whole energy system powered by renewable energy. It includes solar PV, air source heat pumps, a thermal store, batteries and controls. Funding of £14,820 was used for technical assistance for an options appraisal, design specification and procurement to identify the best options, with £84,875 received to cover the actual works. The system enables the members to maximise the on-site use of the energy generated by the solar PV and to optimise the use of each component.

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