How much solar power do I need for my leisure battery?

For those looking to power their caravan, camper van or camping appliances such as lights, a television, oven, kettle and so forth, a solar panel can deliver the dream of free electricity and make self-sustainability a reality.

First however, you need to ensure that the battery that you buy will be suitably sized to power all of your appliances and to keep providing electricity overnight and on gloomy days. To do this, you need to work out your power requirements by finding out the consumption in watts of each device that you wish to power. This will either be on a label on the item, or in its handbook, instruction manual or online. If the power consumption is listed in Amps rather than Watts, simply multiply this by the voltage that the device runs on to convert it to Watts.

You will then need to multiply each device’s Watts consumption by the duration for which you intend to use it every day to provide the device’s daily consumption. Make a list of every item’s daily consumption, dividing it by those which work on 12V or 5V power supplies (such as those intended for automotive, USB or caravan use) and those which work on AC (domestic power supply). To ensure that you account for inverter efficiency loss, multiply the AC power supply list by 1.15 and add it to the total for the 12V and 5V list to get your total daily consumption, which again will be in Watt-hours. This is the minimum amount of power that you will require on a daily basis.

To calculate the storage figure that you will need to maintain power should you experience several days of overcast, cloudy or other inclement weather, you should determine how many consecutive days you are likely to experience these conditions and remain reliant on your leisure battery for power. Multiply your total daily consumption by this number of days to give you your minimum storage figure – that is to say, the minimum usable battery that will be appropriate for your needs.

A solar panel will typically capture one hour a day of power generating sunlight in the winter, compared to six hours a day during a typical summer’s day. To determine how many Watts of power a solar panel will supply to your battery, calculate the Wattage of the solar panel (its rating) by the number of sunlight hours it will be exposed to provide a total Watts per day.

If you will be entirely reliant on your leisure battery and solar panel setup to deliver your power requirements all year round, you will need to know that you can generate your total daily consumption in less than a day and if there are any doubts about your ability to do this, then you should either invest in a backup power supply or determine at the outset which appliances you can do without to reduce your consumption and extend the available power over a longer period.

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