Energy Storage Systems – Solar Batteries

Energy Management & Storage

Finally, the use of globally beneficial & renewable technology doesn’t have to come at a financial loss. Generating your own solar power is already cheaper than purchasing power from your energy supplier, and an Energy Storage Systems (ESS) can help you to save even more.
solar battery drawing
The ability to store solar energy in new Energy Storage Systems, coupled with energy monitoring technology, is re-defining the future usage of solar energy. When you consider the constant rise in electricity costs, falling FIT prices, and their significant drop in price, solar batteries are quickly becoming a more popular and feasible option. But what is an ESS?

Energy Storage Systems cover a wide range of technologies, from batteries to flywheels, from heat blocks to hot water stores. For the purposes of this summary we are referring to electricity stored in batteries. There are numerous types of batteries, each with their own advantages and disadvantages; again, this document refers specifically to Lithium Ion or Lead Acid types.

Here at Solar South West, we believe that Energy Storage Systems define the future of PV energy usage. We want to explain to you why, and how you can use them, to save money and emissions by running off of solar for longer each day.

So why are Energy Storage Systems so Revolutionary?

Traditionally, the problem facing the solar industry has been its inability to supply electricity demand outside of daylight hours – hence the main benefit of solar battery storage.

Generally, and especially through the spring to autumn months, A PV system will generate much more electricity than is needed during the day, and no electricity at all towards your evening usage (when there is no light). This has, until now, made it impossible to run solely off of solar energy.

Surplus energy is the energy which you generate during the day that doesn’t get used, and is one of the key enabling factors of new solar battery storage technology. To understand why, see the image below which illustrates the energy profile of one of our sites over 24 hours during a weekend.

Solar battery energy storage, generation and consumption graph

Within the top half of the graph, indicated in red, is the energy drawn from the national grid. Solar energy provided by the PV system, on the other hand, is indicated in green.

The bottom half of the graph displays the energy generated by the PV panels. Solar energy used by the site is shown in green, and surplus energy which was exported in yellow. As you can see, the site used a fraction of the solar power it generated, having to export a vast amount instead.

How does a solar battery work?

The diagrams below demonstrate how an ESS will work alongside your PV system.

The image to the right represents the energy profile of a site with PV but no battery.

Note the surplus PV electricity which was exported in green. If this surplus had been stored, it could have been used in place of purchasing more from the grid (shown in red).

The image to the left represents a site with both PV and a solar battery.

With a battery in place, the site was able to store their surplus energy (green), and discharge it during the mornings and nights, increasing self-consumption and drastically reducing how much the site had purchase.


During the Day, your PV system will be generating electricity. With an ESS in place, the system will monitor electricity usage, and it will save the surplus, storing it in your battery.

During the Night, your PV panels are no longer generating electricity, but your now fully charged battery will discharge the power it stored – supplying your home with renewably generated electricity.

‘But I’m paid to export my surplus energy…’

As anyone with PV installed will be aware, feed in tariff (FIT) incentive schemes allow the export of surplus energy to the national grid for a fixed price. With that in mind, why invest in a battery if you can get paid to export what you don’t use anyway?

Well… The FIT scheme in the UK pays a deemed export amount of 50% of your total kWh generated (x an export tariff, currently 4.9p/kWh). In other words, if you generate 10 kWh of electricity, you are paid 4.9p for 5 of those 10 kW.

To put this into perspective, the current price to buy 10 units of energy (kWh) typically costs £1.50. Whereas for every 10 units you generate and export, you receive £0.25 (0.5 x 10 x £0.049 current export rate). On systems that were installed in earlier Feed in Tariff years, this difference is even higher.

So, by selling energy in the day, and buying it back for roughly 6 times the price, you are effectively making a substantial loss on every unit you export.

In addition to this, currently, for PV systems <30kWp, your ‘deemed’ export payments will not be affected by the installation of an ESS, as they are 50% of what you generate, and your generation will remain the same.

If your total installed capacity exceeds 30kWp, you will have an export meter, and your export payments will be affected. However, due to the huge difference between purchase and export prices, you will still make significant savings.

The benefits

The main benefit to installing a solar battery system is clear. By increasing your self-consumption, you will reduce both your electricity bill and your carbon footprint.

With every unit of electricity you buy costing roughly 6 times more than you receive for exporting, building a financial case for an ESS should be relatively straightforward. These savings will be significant and immediate, and will increase exponentially as the price of electricity increases.

Further, in the near future, owners of ESS will potentially have access to a number of other revenue streams; for example, through aggregation with others, participating in community energy schemes where you can sell your surplus power to another participant; through assistance to the local Distribution Network Operator in balancing and stabilising the grid.

For larger commercial clients, ‘behind the meter’ storage solutions open up a still wider array of potential revenue streams, most of which are available immediately. To discuss these in more details please contact us for more information.


Be sure about your investment

Batteries currently have a high capital cost, and although there are many immediate benefits, it should not be assumed they have a short payback time.

Prices are dropping, but even so, forking out on a new piece of technology without real evidence to quantify the benefits, is not a sensible investment by any means. What we advise first of all, therefore, is energy monitoring.

Energy Monitoring

Energy monitoring is an effective method of simultaneously reducing your bills through simple energy management, whilst providing in depth, real-time data about your PV generation and usage. We can then use this data in regard to ESS, to tangibly demonstrate figures such as payback periods, through financial models drafted around your own personal energy profile.

Not for profit, Regen SW, state “the variety of energy storage technologies and their applications is enormous.”

In order for a storage system to be cost-effective, you need the right battery to support your PV array. It is for this reason that we believe data analysis is such a crucial step prior to ESS instillation.

Through live data analysis, Solar South West will optimise your consumption, whilst accurately sizing and modelling how energy storage will work for you. Studying your demand is the best way to save money without any large capital expenditure – this service isn’t exclusive to ESS!

Because we understand appliances, plant and machinery, lighting systems and generation from domestic through to large commercial systems, we will analyse then recommend and implement solutions that save money from day one.

Should you decide to benefit from these monitoring services, but not to commit to the investment of a battery, that’s OK too. You will gain access to information regarding your consumption habits, which will allow you to minimise over-consumption, energy bills and your carbon footprint, through a much more intelligent and informed consumption of energy. Once you have achieved this, you are in the perfect position to consider a battery later on, should you decide.

solar south west, somerset based solar technology provider's logo

It is imperative to us at Solar South West that you are given an accurate picture of what an ESS will do for you, whether or not it is cost effective, and what can be done to maximise your self-consumption.

At Solar South West we pride ourselves on our technical know how. After years of tailor making bespoke PV systems, our practical knowledge is unrivalled. Should you decide a battery system is right for you, not only will we install and maintain that system, we will ensure you end up with a long term secure asset and profitable use of your stored PV energy.

For more information regarding Solar Battery Systems, get in touch via the Contact section of our website, or subscribe to receive our free newsletters below.