When buying solar panels you should factor in the available space you have for the panels.
If you are placing them on your roof this will dictate the number of panels you can have and you will probably need planning permission, check with your local council as the rules are changing daily.
Various solar panel mounting options are available for static or mobile use here
Panels come in different sizes, voltage and Watt Ratings, 25W upwards and vary in dimensions.
You may be tempted to buy flexible solar panels, but i would deter you from doing so.
They are not efficient and tend to degrade quickly.
They may seem tempting to those with motorhomes or vans, but they really are a false economy.
If your ground mounting or perhaps installing on a boat, caravan or motorhome, the rules are more relaxed.
Another factor is the direction the panels should face for optimal results.
Many panels will produce energy even in cloudy conditions, but reduced in output.
This may means you will need more panels to compensate.
I would always suggest over sizing the solar panel requirements by about 20% due to the unpredictable weather the UK receives.
Do not confuse daylight hours with sunlight hours.
You may well have 12 hours of daylight, but may only have 4 hours of direct sunlight.
This will need to be factored into your calculations.
Hopefully, you have now determined the size of battery bank needed to meet the total watt hours required.
Example 2400wh battery bank divided by the total direct sun hours, e.g 4 Hours.
The math is 2400Wh battery needed divided by total sun hours 4 (2400/4 = 600)
Using this formula we now know we need a minimum of 600 watts solar panel output.
You can then buy 3 x 200 watt solar panels or any combination of wattage to meet or exceed this number.
Every solar panel will have a sticker showing you the important data you will need to know.
The main information we need is the panels wattage rate or (Pmax) number.
For example a 12v Renogy 200 watt panel (Pmax) number is 200w.
It has a (Voc) number (open circuit voltage) of 27v which means the optimum power it will produce in bright sunlight with no load being drawn.
The (Isc) number is a good guide to what wire sizing to use, in this case its 9.66 amps so we can use wire rated for 10 amps and above.
The max system voltage tells us how many volts we can have in our solar string,
in this case it is 600 Volts DC.
Max series fuse rating tells us the size of fuse we will need if we have more than one or more panels connected in series.
With the Renogy 200w 12v panel it is 15 amps.
You will also see temperature coefficient range which indicates how the panels performance changes in certain climate conditions.
Once you have chosen your solar panels, you will need to get a solar charge controller.
Not everyone has the option to install solar panels and it may not always make financial sense either.
Return on investment may take many years on a residential solar system.
Here's how you can still save money and speed up the return on your initial investment.
Everyone can benefit by using batteries - even those of us without solar panels.
All you have to do is charge up your battery when energy is cheapest.
Then later on, when energy is in high demand you can run on the cheap energy you've saved up instead.
This makes a lot of sense, especially if you can get yourself a good off-peak rate.
You will still need a suitable inverter!
Octopus Energy offer some pretty good rates for those using a battery system at home and electric car owners. Shop around and find yourself the best rates. The savings can be substantial, you are buying cheap electricity and using during peak rates. How to size solar panels solar panel price