Solar Batteries: Who Makes the Best Solar Battery?

Compare solar power batteries

This article was updated in May 2019

Did you know that in just one hour the sun radiates more energy than the whole world uses in a year? That’s free energy that the vast majority of us are missing out on, but solar battery storage systems are changing the game.

Solar panels transform the sun’s energy into power for our homes, but solar batteries enable us to store it for those times when the sun isn’t around. This technology means we can store more of the free energy produced by our panels and buy less from energy suppliers, saving money and increasing our independence from the National Grid.


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Why Get a Solar Battery?

    • Energy bill savings: By storing energy during times of lower demand you can reduce the amount you need to buy from your energy supplier when energy usage is higher, saving you money on your energy bills.
    • Backup Power Supply: Some solar batteries will enable you to use your solar electricity when there is a power cut so you’re not left without power or lighting. When a power cut strikes a store of this energy could be invaluable to your household.

Not all solar batteries enable you to use solar electricity during a power cut, so if this is a priority for you make sure you choose a battery which has this functionality. When there is a drop in voltage on the grid, solar batteries detect this and will automatically turn off the inverter and disconnect your battery from the grid as a safety precaution; engineers will be working on electricity lines on the grid and if batteries are connected to it there is a risk of electrocution. This is called islanding and is essentially a safety barrier between your incoming supply and your fuse board.

If a back-up electricity supply is important you need to be looking at an AC coupled system. At the time of writing, we were only able to find 2 battery systems available in the UK that will keep the lights on during a power cut. The  Tesla Powerwall 2.0 with the Back-up Gateway. This updated version of the Powerwall 2.0 comes with a separate unit which looks like a smaller version of the battery itself and completely islands your home in the event of a power cut. The second and much cheaper option is the PureStorage battery system from PureDrive.

Find out more about solar back-up batteries and power cuts here.

  • The Feed-in Tariff (FiT) Scheme Has Closed: Back in 2010, the government introduced the Feed-in Tariff scheme which paid owners of eligible PV systems for every kWh of energy they generated and each kWh of unused energy which was exported to the National Grid. Although this scheme was a great incentive for homeowners to install solar panels, it also prevented some homeowners from installing a solar battery as they feared they would receive lower payments if they did not send their surplus energy to the grid. The FiT scheme closed to new applications in March 2019, so if you are yet to install solar PV you won’t be paid for sending send your surplus energy to the National Grid and will save much more money by keeping hold of it.

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The Best Solar Batteries & Prices

Solar battery prices can range from £500 to well over £10,000 excluding the cost of having it fitted. We estimate installation charges to be at least £500 worth of an electrician’s time for a simple plug and play battery and up to £2,000+ depending on the complexity of the system you want. You may also have to add the cost of an inverter if retrofitting solar batteries to your existing solar panels which could be around £1,000. It’s worth noting that there are quite a few ‘hybrid’ systems which combine an inverter and battery storage.

The table below details all you need to know to make a fair comparison but as price is a major factor in any major purchase we’ve extracted the prices out for quick reference and categorised them as either a full energy storage system (includes an inverter) or a battery on its own that requires a separate inverter if you want to connect it to a solar pv system.

 

Full Energy Storage systems

(Battery + Inverter)

  • Tesla Powerwall 2.0 with Backup Gateway 2: £7,900+
  • Energy Storage System by PureDrive: £3492+
  • Samsung SDI ESS: £3,500+
  • xStorage by Nissan: £6,446+
  • Enphase: £1,700+
  • Sonnen Batterie Hybrid: £4,500+
  • Powervault 3: £2,000+
  • Moixa Smart Battery: £2,950+

Battery only

(requires an inverter if connecting to solar panels)

  • LG Chem Resu: £2,628+
  • Sonnen Batterie Eco: £4,500+
  • BYD B-BOX: £1,700 +
  • OVO: Unknown – currently being trialled by OVO customers
  • Solax Triple Power: £1,920+
  • Varta Pulse: £3,579+

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Supplier Capacity Technology Cycles Warrantied Warranty Weight Operating Temperature Dimensions (mm) Mounting Powercut backup** Cost*
Tesla Powerwall 2.0 Tesla Powerwall 2.0 13.5 kWh Lithium-ion n/a 10 years 125kg -20°C to 50°C 1150 x 755 x 155 Floor/Wall Yes £7,900+
LG Chem Resu 6.5 solar battery storage LG Chem Resu 3.3 – 9.8kWh Lithium-ion 6,000 10 years 31 – 99.8kg -10°C to 45°C 452 x 403 x 120 to 744 x 907 x 206 Floor/Wall No £2,628+
sonnenBatterie Eco Sonnen Batterie Eco 2 – 16 kWh Lithium-ion 10,000 10 years 71 – 273kg 5°C to 40°C 702 x 641 x 221 to 1839 x 641 x 221 Floor/Wall Yes £4,500+
Powervault ECO Battery Powervault 3 4.1 – 20.5 kWh Lithium-polymer >6,000 10 years 129 – 329 kg 0°C to 35°C 120 x 98 x 25 to 205 x 98 x 25 Floor/Wall No £2,000+
Enphase Solar Battery review Enphase 1.2 kWh Lithium-ion 7,300 10 years 25 Kg -20°C to 45°C 390 x 352 x 220 Wall No £1,700+
Samsung SDI Solar Power Storage Samsung SDI 3.24 kWh Lithium-ion 6,000 5 years 95kg -10°C to 40°C 1000 x 267 x 680 Floor Yes £3,500+
moixa storage battery Moixa Smart Battery 2-3 kWh Lithium Ion Phosphate – LiFePO4 10,000 10 years *Lifetime with GridShare 3 – 49kg -5°C to 40°C 505 x 345 x 245 Wall No £2,950 – £3,450
Nissan xstorage xStorage by Nissan 3.6 – 6 kWh Lithium-ion n/a From 5 years for 4.2kWh system, 10 years for 6kWh system 135kg 0°C to 30°C 1230 x 890 x 220 Wall No £3,000
byd bbox BYD B-BOX 2.5 – 409 kWh Lithium Iron-Phosphate n/a n/a 88 – 202kg -20°C to 55°C 1000 × 600 × 600 Floor No £1,700+
ovo battery OVO Home Energy Storage 4.2 – 10 kWh Lithium-ion n/a n/a 96 -122kg n/a 650 x 300 x 1080 Floor No n/a
solax battery Solax Battery 3.3 – 6.5kWh Lithium-ion 3,000 10 Years 26 – 44kg n/a 330 x 450 x 110 Wall Yes £1,920+
varta pulse battery Varta Pulse 3.3 – 6.5kWh Lithium-Ion 10,000 10 Years 45 – 65kg -5°C to 30°C 330 x 450 x 110 Wall No £3,579+
Puredrive purestorage solar battery Puredrive ESS 4.8 kWh LiFePO4 Lithium ion Phosphate 6,000 10 Years 79kg -20°C to 60°C 740 x 740 x 310 Floor/Wall Yes £3,492+
*Prices are estimates only and do not include installation costs which can range from £500 to over £2,000. **powercut back-up may be an optional extra and not be included as standard
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How do solar batteries work?

Solar panels are fitted onto a roof or exterior wall where they can be exposed to the most sunlight. Each panel includes solar cells which convert the sun’s energy into DC electricity which is then converted to AC electricity by an inverter. This can then be used to power your home.

Whatever you don’t use is sent back to the National Grid to be redistributed around the country. This means that you can only use solar energy as and when it is available, i.e. when the sun is shining. However, this is not the case if you install a solar battery…

By introducing a solar battery into the process you can keep hold of the surplus energy you’ve produced for use at another time (e.g. at night) and further reduce your reliance on the National Grid.

Fitting a solar battery to your home


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Solar energy systems that can store their own electricity have three main components:

  • Solar panels that absorb and convert the sun’s energy to DC electricity.
  • A battery (or batteries) to store the electricity that is not used for use when the solar panels aren’t generating electricity.
  • An inverter that converts DC electricity to AC ready for use in your lights, appliances etc.

As solar technology continues to progress many modern systems also incorporate smart technology such as apps and Wifi so you can easily monitor the battery’s charge level and general efficiency.

Types of Solar Batteries

AC or DC?
The solar battery you choose needs to be the right size or voltage for your needs. This is very important as the wrong size could pose a very real safety risk. We highly recommend consulting with multiple professional installers about your needs before reaching a final decision.

In addition to choosing the right voltage, you will need to consider if AC or DC is the best choice for your system. The main difference is in the way the battery connects – or doesn’t connect – to your solar panels.

AC: An AC (alternating current) battery is not connected directly to your solar panels but is connected via the electricity meter. This means it is easier to retrofit to existing panels, so if you have solar panels already in place this may be the best solution for you. You will need an additional inverter to convert DC electricity to AC for use in your home and then back to DC to be stored in the battery. Powervault 3 is an example of an AC-coupled system, while Tesla’s Powerwall 2.0 is an example of a DC-coupled system.

DC: DC (direct current) batteries tend to be installed at the same time as solar panels as they connect directly to the panels. You do not need an additional inverter as it is connected before the electricity meter.

Lithium Ion Vs Lead Acid

All of the solar batteries featured in this article are Lithium-ion based, this is the more progressive technology and the same battery technology you’ll find in your lap-tops, mobile phones and electric vehicles. There is still a strong and well established market for lead-acid batteries (the kind you’d find in your car) and they are still popular with many solar power users who live off grid. Lead acid batteries are tried and tested technology that dates back over 100 years and they are cheaper in terms of upfront cost. However Lithium-ion batteries have a lower life-time cost and operate at a much higher efficiency level.


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Things to consider

Ongoing Maintenance
A solar battery is not a simple ‘install and leave’ unit. It needs regular monitoring and maintenance to keep it working both efficiently and safely. This includes keeping it charged at an optimum level, carrying out regular power ‘boosts’ and gassing as well as ensuring it is stored at a correct temperature and protected from the weather.

Replacement Parts
Solar batteries do not last as long as solar panels. Currently, a high quality solar battery will last for around 10-15 years, but this is dependant on how much you use it and ensuring it is maintained correctly. A battery can cost up to £2,000 (not including installation) so it is a significant expense to consider.

It’s not a complete energy solution (yet)
The ultimate ambition for many is to make complete energy self-sufficiency a reality, without any reliance on the National Grid at all. While technology is certainly moving in the right direction and has made great strides in recent years, a solar battery system is still not a viable option to completely disconnect from the mains supply. Batteries have their faults, shelf-lives and limitations, so until things have progressed it’s necessary to have the option of a backup supply from the National Grid.

Solar Battery FAQs

Do you need solar panels to have a solar battery?

No. If you live in an area affected by regular power cuts then a home battery could be just the system you need to keep the lights on. On average you’ll probably get around 24 hours of backup power but this can be increased by simply installing more batteries. If you’re on an Economy 7 rate a home battery can also save you money by charging when electricity is at it’s cheapest for you to use when it’s not so cheap. Finally, you can even make money by storing energy for the National Grid who can discharge it from you in times of need.

Can you add a solar battery to existing solar panels?

Yes and no. Some batteries will only work when installing a new system or one that was specifically designed for it (Tesla Powerwall 2) and some systems will retrofit to any system.

Are solar batteries safe?

They are as safe as as any other electrical item in your home. Generally installing a solar battery is not a DIY job and for the most part the public can’t buy solar batteries direct from the manufacturer but rather via an approved installer.


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Jargon Guide

      • Capacity: This is the ‘usable’ amount of energy in kWh (units) that the battery will store. It’s never a good idea to run a battery down to empty as it will cause damage, so when you are comparing capacities remember to check if the figure given is ‘total’ or ‘usable’.
      • Cycle: The number of cycles refers to the amount of times a battery can be charged and discharged. It will give you an indication of how much ‘life’ a battery has but doesn’t relate to the number of years it’s been operating.
      • Technology / chemistry: Batteries are generally Lead Acid or Lithium Ion. While acid is cheaper it is not as efficient and doesn’t last as long as Lithium Ion.
      • Power output: This is, quite simply, how much power the battery can deliver at one time. The more appliances / lights etc. that you plan to power with the battery the higher this will need to be.

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