How Much Power Does A 100w Solar Panel Produce? (Part 1 Of Series)

If you are just getting into solar, this short guide can save you ALOT of time!

While doing your solar panel and solar system research, it can be extremely confusing trying to figure out all the calculations and conversions.

The good news is you can use this guide for estimations in figuring out how much power a 100 watt solar panel produces.

100 watt solar panels are usually used for off-grid type situations or powering standalone DC or AC items, rather than powering your house.

Solar systems can come in 12, 24 and 48 volt systems – but, we’ve calculated based on 12 volt because it’s the cheapest, and it’s what most people use.

You’ll get a rough idea of the power a 100 watt panel produces below.

Let’s get into it…


How Much Power Does A 100w Solar Panel Produce?

To figure out how much power a 100 watt solar panel produces, you can make the following considerations and calculations:


1. Consider and calculate power loss

The first thing you should know is that the solar panel company says the panel is a 100 Watt panel, but 100 Watts doesn’t take into consideration how a solar system works in reality with inefficiencies and power loss.

Power loss and inefficiencies can be caused by:

  • Efficiency/conversion of the particular panel when sunlight hits it, and then converting that sunlight into energy
  • The solar controller you use when the power comes from the panels through to the battery (used when charging most 12 volt batteries)
  • The solar inverter you use when you convert from 12 volt to say 115 volt (an inverter is used for AC household items or charging back to the grid)
  • You also lose some power across the length of your connectors or cables
  • + other minor factors and variables


How to calculate power loss and inefficiency?

This one is pretty simple.

You can subtract 20% from your panel – so, a 100 Watt panel actually becomes an 80 Watt panel (100 – 20 = 80).

So, we now have a 100 Watt panel which is producing 80 Watt per hour.


NOTE: some people might subtract 10% now for the inefficiency of the panel, and then choose to subtract 10% later when they figure out their final load or charging numbers to account for the controller, inverter, cable and other inefficiencies, but it’s up to you.


2. Consider and calculate number of available sunlight hours

The second thing you want to consider is how many daylight hours you get in a day where you will be using your solar panel.

The absolute maximum sunlight hours you might get will usually be around 8, but in most areas, you will get around 4-5 hours of direct sunlight on your panels.


How to calculate available sunlight hours?

Let’s say you decide you get on average 5 sunlight hours in your area.

You would multiply 80 Watts x 5 hours = 400 Watts per day

So, your 100 Watt solar panel is producing 400 Watts of power a day

Note though, that if you have a cloudy or rainy day – you might get zero direct sunlight hours, and your power produced could be zero for that day.


3. Summary

So, that’s how much power a 100 watt solar panel produces…

  • A 100 Watt solar panel actually becomes an 80 Watt panel when you factor in inefficiency and power loss
  • That same 100 Watt panel, with 5 hours of direct sunlight a day will produce 400 watts a day of power


4. What To Do Next?

To calculate your whole solar system, next you’ll want to know

  • what a 100 watt solar panel can power (how many and what items can a 100 watt panel power, and how to calculate the watts that each item uses)
  • how many 100 watt panels you need for your system
  • how long and often to charge your 12 volt deep cycle battery to keep your solar system charged

You can find out those things in Parts 2 & 3 of our Solar System Estimation Series  –


A few things to note and be aware of:

  • You can get 12, 24 and 48 volt solar systems. These estimates are based on a 12 volt system, because it’s the cheapest and it’s what a lot of people start with. If your battery bank changes to 24 or 48 volt – you’ll need additional panels, and suitably rated solar controllers and converters.
  • When using solar charge controllers (for DC charging) and/or solar inverters (for AC charging), make sure they are rated for the power and voltage you have running through your system
  • How your solar panels are wired or connected up i.e. whether they are stacked together, and/or if they are connected to individual or combined controllers, inverters and batteries effects charging setup
  • Always consult a professional, and the relevant authorities before installing and using a solar system. These guides are for estimation purposes only.

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