Battery Storage

The simple answer is that the home battery system stores electricity for use in your home at another time. The demand for energy within the home isn’t at one level all day, especially if there are periods when some or all of the family are out of the house. This means that for some periods of the day, the electricity being generated by their solar panels isn’t being fully utilised. Of course, when the sun goes down or the weather is particularly bad, the solar PV can’t generate electricity, and you need to draw from the grid to power your home. A home battery means that you have solar energy stored to use before you need to take from the grid.

At present, there are two main battery technologies used in the UK, these being lithium-ion and lead-acid. Our expert installing team of solar battery storage installers will be on hand to guide you through the process to understand which is most suitable for you and your home.

As for the science behind solar battery storage, put simply these systems work by storing excess energy produced by your solar panels. When the sunlight hits your solar panel, the cells in the panel will convert this sunlight into a direct current (DC). This DC electricity will then flow through to an inverter, which will convert the direct current into an alternating current (AC), the form of electrical energy that can be used by household appliances in the UK. In times where the demand for electricity is lower than that which is being generated, the DC current can be taken directly from the solar panel and used to charge the solar battery system directly. Then, later on when the demand for electricity is greater than what is being generated by your solar panel, the battery will discharge power.

As a renewable energy source, solar helps reduce these harmful emissions by reducing the demand for fossil fuel resources. Although it may not seem like one home can make a difference, just one 5 kilowatt system is the equivalent to planting 150 acres of forest, removing over 100 tons of carbon emissions, or taking two cars off the road.

Not every solar system requires a battery, but they can be beneficial in certain cases. Batteries can help mitigate demand-based utility charges, which raise rates at peak times. They can also be useful as backup power in areas with frequent power outages.

If your property already has PV installed and you want to add a battery at a later stage, you will need to have a separate battery and PV inverter installed. This is because the battery is essentially joined to the PV system after the AC conversion has already been completed.

In terms of physical dimensions, the battery and inverter in total will be just over a metre in width and up to to metres in height. These systems can be housed in a convenient location out of the way such as a utility room or garage.

There is no one best location for a battery within a house; our detailed survey will identify the best location for the battery. It will need to be relatively close to the main unit, however we will always endeavour to place it somewhere out of the way such as a cupboard.

Yes, many modern solar batteries can go in the loft as long as they are lightweight enough. When it comes to the installation, sufficient access to the loft will be required as the batteries can be rather large.

Whilst you do not need storage systems for your PV panels to work, we highly recommend them as a way of maximising your renewable energy generated for yourself.

With home battery systems that you use your solar PV system to charge, there are two ways to answer this question.

The amount of time that the solar battery can run your home will depend on the capacity of the battery system and the level of charge. Some home batteries, like the Tesla Powerwall 2, could potentially power your home for more than 24 hours from a full charge, because the capacity of the battery is more than the average daily household usage of electricity. However, if it is only partially charged, or if you have a battery system with less capacity, the energy won’t last as long when powering your home.

In terms of the life span of a home battery system, this can vary; depending on the make and model of your battery and the way that you use it. Whilst these types of batteries are designed and optimised to undergo frequent charging and discharging, eventually, over many thousand cycles, the batteries will start to lose a small percentage of capacity. Professionally installed home battery systems will always come with a warranty, which are usually around 10 years, and are guaranteed to maintain a certain level of performance e.g. the Tesla Powerwall 2 has a warranty for 10 years for 80% of the original capacity; so, if your battery isn’t storing at least 80% of the energy it did when new within 10 years, Tesla will replace it.

From our own experience of these products and the very slow degradation of the types of batteries used in the home battery systems, the likelihood is that a home battery system will usually significantly outlast the warranty.  It is the same as any other electronic product in this respect – if you bought a TV with a 5 year warranty, you would reasonably expect it to last for 10+ years.

We can advise on the best home battery system for your needs and make sure that all warranty information is clearly understood, on all aspects of the installation. Get in touch today for more information.

If you currently receive feed-in-tariff (FiT) payments for the electricity you generate with your solar PV, they will not be affected if you install a home battery system. The FiT scheme was discontinued for new home solar PV systems installed on or after 1st April 2019, but existing qualifying households won’t lose any of these payments for the contract term (usually 20 years from installation) if they do install a home battery system.

Different home battery storage systems may come either ‘AC coupled’ of ‘DC coupled’. A DC coupled battery system, locates the battery between your panels and the inverter (which converts DC electricity to AC electricity for use in the home.  DC coupled systems are more thermodynamically efficient, as you only convert DC to AC electricity once.

An AC coupled battery system has a separate inverter in the battery itself.  Solar DC electricity is converted to AC electricity for use in the home, and if it goes into the battery is converted to DC again.  This is thermodynamically less efficient, but much more flexible.  It allows batteries to be charged from any source, not just solar.  They can be charged from the grid, for example when electricity is cheap, typically when there is a lot of wind power on the national grid.  So it allows you to take advantage of cheap low carbon electricity no matter where it is generated.

It also means that the battery doesn’t need to be installed physically close to your solar PV inverter, which makes installation more flexible. For these reasons, the market is moving towards AC coupled systems as standard.

Regardless of whether you choose a DC or AC coupled battery storage system, it should be possible to install it with an existing solar PV system, when using an experienced MCS approved installer like Solar Dynamics.

If your household has very high energy requirements in the evenings, especially during longer winter nights, smaller battery storage systems may not be able to hold enough power for all of your needs all night. Home battery systems are also limited to the amount of electricity output they can give at any one time. It’s important to choose a battery storage system for your home which is best matched to your household’s needs. 

The size of the home battery system that you need will depend on the size and energy requirements of your home. The average household uses between 8-10 kWh of electricity per day. Home storage batteries start at around 2.5-5 kWh in capacity for small systems, up to the larger systems which offer around 13-15 kWh of energy storage.

We would typically size a system by following a two step approach:

Economically, the ideal size for a battery is one that would cover your evening and night-time usage (with a little to spare, just in case). Your electricity demand will empty the battery by next morning, meaning it has the maximum possible space to capture the next day’s sunshine.
We then sense check this against the size of your solar PV system. Obviously, there’s no point having a large battery if your generation is small – as you’d never be able to fill it.
So in practice, some home battery systems are sized to the demand of the home, but in some cases they are sized to what the solar PV system can produce.  Getting this right is complex, which is why our expert engineers are on hand to help you find the right system for your home.

You will need to bear in mind that home storage batteries might well not receive enough energy to charge every day (depending on the weather and how much solar electricity your home generates and uses). 

With a correctly-sized battery system for your home in the UK, you should ideally have enough energy waiting to meet your evening and overnight needs for the majority of the year, but are likely to need to draw electricity from the grid in the winter months.

We would never use or install a brand of home battery that doesn’t come with a warranty. All of the major manufacturers of these systems offer a warranty, usually around 10 years in length, although there are some restrictions and caveats on usage for some products. 

The cost of a home battery system will vary, depending on the make and model of system that you choose. You will also need to consider installation costs, which can also vary, depending on the complexity of the work that needs to be done. For example, some of our customers choose to upgrade their solar array and/or install an EV charging point at the same time as we install the home battery system, which can mean a big saving on having these three things done separately. Some installations may require a separate inverter be fitted and some will be able to use the same inverter as your solar panels. We can offer expert guidance as to the best system for your existing setup and home.

The cost of a home battery system will depend not only on the brand of product, but also the size/capacity of the battery itself. Currently, the Tesla Powerwall 2 offers great value per kWh of storage, but if you are a smaller or less busy household then you may be better off with a smaller and cheaper system with less energy storage capacity.

It’s very difficult to say how much a home battery will save you, as it is highly dependent on both how much you personally use and how much you can generate.

Our analysis has shown that a battery can actually improve the payback of a solar PV system in some circumstances.  Where the solar PV system is large, the battery can be filled from solar PV for a greater proportion of the year, which improves the overall economics of the home generation system.

We also know that where this is not possible, having the ability to top-up with cheap grid electricity when solar is not available, also massively improves the return on investment.

Overall, battery paybacks tend to sit in the 10-15 year range – this is above the warrantied lifetime, but within the lifetime that you might expect the product to last, as we have noted above.  We therefore consider battery storage systems as a broadly cost-neutral way for you to increase your own self sufficiency, and to be less reliant on more polluting grid electricity.

If you’re getting a home battery that works with your solar PV system, you will need to ensure that your installer has the necessary experience to carry out the installation properly, so that all of the necessary elements communicate properly with each other. It is advised that you use an installer with years of experience in both solar PV installations and home battery systems.

We are fully signed up to the Renewable Energy Consumer Code, which enforces high consumer protection standards, following the consumer journey from start to finish, for businesses who are selling or leasing renewable energy generation systems to domestic consumers.