Solar Panel Battery Storage for Homes

The hope of incorporating efficient electricity storage with solar energy systems has lingered for many years. The dream is that solar battery technology will advance to a stage where it becomes both practical and commonplace to store excess electricity generated by solar PV systems for use later in the day or during the night, offering a significant boost to self-sufficiency for your home.

For houses with a three phase supply, we offer a SolaX solution which stores surplus energy produced by solar.

At Solar Voltaics, we’ve chosen to feature two of the most advanced solar battery systems available on the domestic market: the Tesla Powerwall 2 and GivEnergy. These batteries not only deliver impressive storage capabilities and reliable warranties, but are also engineered for effortless integration with smart energy tariffs such as Octopus Agile and Octopus Go. When you couple residential battery storage with one of these ‘time of use’ pricing schemes, you open the door to substantial energy cost savings in your home.

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Tesla Powerwall 2

Powerwall’s lithium ion battery inherits Tesla’s proven automotive battery technology to power your home safely and economically. An integrated inverter reduces external components, which simplifies and lowers installation costs. Powerwall is a completely automated system that requires no maintenance. The Tesla Powerwall 2 AC is a fully integrated AC battery system for residential or light commercial use. Its rechargeable lithium-ion battery pack provides energy storage for solar self-consumption, load shifting and backup power.

Fully installed from £9,550 + VAT (No VAT if installed with Solar!)
Large stocks on order.

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GivEnergy

Hybrid inverters are ideal when installing solar and battery storage at the same time. The hybrid inverter converts DC power from the solar panels into AC mains power, but also manages when to charge and discharge the battery. Because all this happens in one unit it reduces the overall cost of the system whilst maintaining high efficiencies.

AC Coupled inverters are ideal where a solar PV system is already installed with an existing inverter. The addition of the AC coupled coupled inverter is purely for managing the battery charge and discharge.

Fully installed from £3,542 + VAT (AC Coupled + 2.6KWh battery) (No VAT if installed with Solar!)

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Understanding Solar Battery Storage

Your solar PV system without Battery Storage

The solar PV system on your roof will generate electricity during the day that you can use in your home. Without a means of storing that solar electricity, any surplus energy that you don’t use is ‘exported’ to the local grid. During times when the panels are no longer generating (or not generating enough for your needs), you need to buy electricity back from your electricity supplier.

Solar PV with added Battery Storage – How it Works

Adding a battery to your solar PV system allows you to store the excess energy produced and keep it to use at a later date, often at night or when the panels are not generating enough power for your home. You will export less to the grid, but in turn you will also use less from the grid, saving you money on your electricity bill.

During the day:

the solar PV system generates solar electricity
the solar battery storage system will check if all the generation is being used to power your lights and appliances
if you’re not using all the electricity that the solar PV system is generating, then the system will ensure that any surplus energy is used to charge the battery
once the battery is fully charged, if there is still more solar electricity being generated, this will be exported to the grid (or in some systems, will be diverted to other uses e.g. to an immersion heater)

Overnight or at time of low solar weather:

The solar PV panels have a reduced or zero output.
The battery system can discharge the stored electricity, providing you with renewable-generated electricity at no additional cost.
Once the battery is discharged, if you need to use more electricity, you buy it from your electricity supplier.

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Battery capacity – What size do I need?

Solar Battery storage systems within homes are often provided with a capacity rating in kiloWattHours (kWh).

Storage batteries for a grid connected solar PV storage system are typically around 2kW to 20kWh. This is the capability of the battery to provide power.

All batteries lose some energy in charging and discharging (typically around 10%), though some have better ‘charge-discharge efficiency’ than others.

Most batteries are not designed to be routinely fully discharged (can reduce battery life). Some have deeper discharge capability than others.

What could a solar battery storage system power?

A fully-charged medium-sized system could store sufficient energy to power during the evening your lights and lower-powered items like your fridge-freezer, TV and laptop. Over four or five hours, all of these together will use at most a few “units” or kiloWatt-hours (kWh), of electricity.

However, the battery will quickly run out if you put on high energy use devices like the washing-machine or tumble-dryer: these can consume 2 – 3kWh in a single use. The higher capacity your battery is, the longer you can run your home without buying power from the grid.

And in winter, the battery might not receive enough energy from your solar panels to provide for even the lower-powered items for many hours. You can compensate for this though by automatically charging your battery up at night on a cheap off-peak tariff.

Power-cut operation

Despite expectations, some storage systems will not provide power during a power-cut.

Some solar battery storage systems however do have an ‘off-grid’ functionality, providing a limited amount of power to your home, or to essential equipment (such as your fridge-freezer, lighting etc). But a battery may run out of power before the power cut ends – or have already run out of power if it’s been discharging all evening and the power outage starts late at night or early in the morning.

If you require your battery storage system to provide power during power-cuts it is important to talk this through with us from the outset as the system will need to be carefully designed and set-up to your specific requirements.

Battery lifetime

A battery’s efficient lifetime depends on the technology and the way the battery is used – significantly on the number of ‘cycles’ (complete full battery charge and discharge) that they undergo. Manufacturers generally give an expected lifetime in years and / or in ‘charge-discharge cycles’. For example:

‘Life expectancy = 10 years or 10,000 cycles, whichever is the sooner’ Lithium-ion batteries last longer than lead-acid: you may see a 10-year lifetime expectancy claimed and this is improving all the time. Normally the solar battery storage system will monitor the battery performance and should give you an indication when your batteries need replacing.

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Domestic Battery Storage