How much battery storage, in ampere-hours, do you need?

To work out what you storage you require take your average daily usage in watts and divide by the battery voltage.  Eg: If you use 3.6 Kwh (kilowatt-hours) or 3600 Watts of electricity per day and your solar electricity system operates at 12 volts, then dividing 3600 by 12 gives you 300 AH.  The battery should not be discharged more than 50%, therefore you will need 600AH of battery storage.

The total battery capacity (in amp-hours) should be five times your daily usage. 5 days of storage or backup is commonly used. 

Numax Deep Cycle Gel Batteries Solar Power
Numax Deep Cycle Gel Batteries for Solar Power Storage

£79

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Numax Deep Cycle Batteries for Solar Power
Numax Deep Cycle AGM Batteries are an ideal solution for low cost solar storage.

£15

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Sonnenschein Solar Gel Batteries
Sonnenschein batteries are manufactured in Germany and have been specifically designed for solar and wind applications.

These batteries are non-hazardous, maintenance free, extremely reliable and can last twice as long as a regular wet cell battery.

£75

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Solar Batteries

There are a wide range of battery technologies available. The Lead-Acid battery is most commonly used for solar power applications as the energy storage costs are lower than other battery types. Lead-Acid batteries operate over a narrow voltage range which makes them ideal for powering common appliances. The disadvantage is that they are easily damaged by excessive discharge.

Starting batteries

Starting batteries such as car batteries are easily available at very low cost. They are designed to deliver a very large current for a short time. Contrary to common belief this does not result in a heavy discharge, usually no more than 5% of the battery’s total capacity. The demands of solar power systems require that the batteries are frequently discharged by 50% or more, and thus a starting battery is unsuitable. Attempts to use starting batteries in this way results in a very short life and is a false economy.

Deep-cycle batteries

The term ‘deep-cycle’ refers to batteries that are designed for regular discharging by 50% or more. The term is applied to many different forms of battery from small 6 or 12 Volt batteries to much larger batteries consisting of separate 2 Volt cells. The majority of deep-cycle batteries have a liquid electrolyte (acid) which is vented to the atmosphere. Sealed types with the electrolyte in the form of a gel are also available, but are more expensive.

Leisure batteries

The term ‘leisure battery’ refers to a battery which is a compromise between the low cost of a car battery and the long life of a true deep-cycle battery. They have a much longer life than a car battery when regularly discharged and are much less expensive than a true deep-cycle battery.