Solar Calculator

Our solar calculator can be used to help you decide the best combination of solar panel power output and battery storage capacity in relation to your planned power consumption. Solar power generation is variable between cloudy and sunny spells so it is best to store the power using a battery when it can then be used at any time of the day or after dark.

You can experiment with the different power solar panels. This calculator will show how much power will be generated at different times of the year. There will often be a peak generation during the summer with excess power and limited generation in the middle of winter. The guidance notes to help you understand some of the terminology below the calculator.


Based on south facing panels mounted at 35 degrees above horizontal, located at a uk latitude of 52 deg n, i.e. manchester. As a guide, the uk south coast and south west england would have around 10% more generation; scotland would have around 10% less solar generation than the figures below.

WattageTo calculate the wattage power consumption of a product, use the following calculation: amps x voltage = watts E.g. 1.5 amps x 240v = 360 watts
AhAn ampere hour (abbreviated Ah, or sometimes amp hour) is the amount of energy charge in a battery that will allow one ampere of current to flow for one hour. An ampere is a unit of measure of the rate of electron flow or current in an electrical conductor.
KWhrKilowatt Hours. For example, one 1 KWhr is 1000 watts used for one hour.
Deep CycleA deep-cycle battery is designed to discharge between 45% and 75% of its capacity, depending on the manufacturer and the construction of the battery. Although these batteries can be cycled down to 20% charge, the best lifespan vs. cost method is to keep the average cycle at about 45% discharge.
RecyclingDeep cycle lead acid batteries are recycled 98% by volume, 99.5% by weight. The plastic cases, lead plates, sulfuric acid, solder, and other metals are 100% recovered for reuse. Always take used lead acid batteries to a recycling centre at the end of their useful life.

NOTE: The usage hours above assume you have had adequate sunshine to fully charge your battery, or your battery has had a full solar re-charge because you have not used it recently.


You may find that in order to full charge larger capacity batteries, especially during the winter months, that you need to design your system with more solar power wattage input, in some cases a multi solar panel array maybe needed.


In some systems, 12 volt batteries will be connected in series (end to end) to create a higher final voltage which may be needed to suit the type of inverter used. For example, two 12 volt batteries in series will provide 24 Volts, or 8 x 6v batteries in series will provide 48V

In the above 12v Battery example, if two 12 volt batteries rated at 100 Amp Hours were connected in series, while the voltage would increase to 24 Volts, the Amp Hours would remain the same. Therefore, whilst batteries in series add the total voltage together giving a higher voltage output, the total Ah capacity of the batteries is not added together in the same way.

An example of why this happens can be seen when comparing batteries wired in series and parallel. For example, 2 x 100Ah batteries in series would give a 24v output at 100Ah = 2.64Kwh OR 2 x 100Ah batteries in parallel would give a 12v output at 220Ah = 2.64Kwh. Battery KWh storage is indicated above below the battery capacity user input box.


A battery solar charge controller will be needed in most circumstances to control the output voltage from the solar panel (usually 18-22 volts) and ensure steady charge to the battery. Our charge controllers also have a 12v output and a 5v USB output.


The natural cost effective choice is to use a deep cycle lead acid battery but please be aware of their limitations as below. Battery limitations may mean it could be better to oversize the battery for you required usage to reduce the depth of discharge and in turn prolong battery life

Depth of DischargeDeep Cycle Battery
100%150-200 Cycles
50%400-500 Cycles
30%1000 and more cycles

Other types of specialist solar power storage lead acid batteries are available which can last for over 2000 deep discharge cycles. These often have specially coated and thicker heavy duty positive plates within the battery.

Lead acid car batteries or similar should not be used for solar electricity storage purposes as they are not suitable for deep discharging due to their thin lead plate construction.


You may wish to use an inverter with your battery in order to convert the output voltage to power 240V AC appliances. Note that whilst inverters are very useful, they do only have an efficiency of around 90% meaning that 10% of your battery storage will be an inefficiency loss. Alternatively, you may wish to consider using 12V DC input lighting and appliances which would not suffer the invert losses.

Solar System Inputs

Typical KWh Generation per Day


Battery Re-Charging time (Days) based on:-

Your Chosen Ah Battery is equivalent to 0.000 Kwh Storage

Please find below Battery Re-Charging time (Days) based on an average day of solar power generation using your selected solar panel size above.

MonthDeep 80% DischargeLow 20% Discharge

Approximate Hours of Usage:-

Based on your anticipated power load on the system of watts, your maximum usage time for this battery capacity would be around 0.0 Hours

Approximate Hours of Usage based on your selected battery capacity in section 2 above with an 80% deep battery discharge (see notes on battery life below)

Other usage examples belowWattsHours of Usage for your selected battery / solar panel combination
Computer (monitor & printer)4000.0
Electric Drill4500.0
Games Console1000.0
Laptop Computer950.0
Small Refrigerator2500.0
TV 13" with dvd player2100.0
10w LED floodlight120.0