To figure out how much solar I need, I have to estimate how much power I will consume on a daily basis. This is measured in Watts. If Watts are not specified on the device label, then I used the formula Watts = Volts * Amps, since this Volts and Amps are always there somewhere.

IPad Charger: 10W

IPhone Charger: 5W

LED light: 3W

Roof Vent Fan: 3 to 50W, depending on speed setting. I'll use the average of 26W.

Total: 44W

How many hours will I be using the devices? Let's say I am using both chargers and one light continually for 10 hours a day, or 180 Watt/hours per day. I do not know how often I will use the Roof vent fan, so I am guessing here: 3 hours on a medium setting so 26x3=78Wh. 180+76=256Wh of electrical usage per day.

I used a calculator I found at https://www.renogy.com/calculators#solar-size

The renogy calculator wants Watts and Hours entered seperately, so I divided 256Wh by 44W and rounded up to 6 hours.

I plugged these numbers into a solar sizing calculator, assuming a PWM controller and 5 hours of usable daylight per day and got these numbers:

Recommended Solar Panel Size: 66W

Recommended Battery Size: 44Ah (Amp hours)

I will need to run AC appliances on occasion, so I will need an inverter.

The devices I need to run occasionally are:

Airbrush compressor (240W)

notebook computer charger (80W)

my printer (10W)

The compressor is the most power hungry, so I will use that for my calculations.

Induction motors such as air conditioners, refrigerators, freezers, microwave ovens, and pumps (like my Compressor!) may have a start up surge of 3 to 7 times the continuous rating. Let's assume the worst, and my 240W compressor will surge 7x to 1680 Watts!

AC inverters are rated in watts, with a surge rating of double their base. So if my compressor surges to 1680 watts, I will need a minimum of an 840W inverter. That is not a standard size, so I rounded up to 1000W.

Some electrical devices are sensitive to power fluctuations, like computers and printers. So a "pure sine wave" inverter is reccomended to provide smooth power.

Let's assume I will run the compressor for an hour a day: 240W for 1 hour. I know that inverters are not 100% efficient, so let's round that up to 300W, and assume the extra 60W is converted to heat and wasted. Plugging these numbers into the renogy calculator results in:

Recommended Solar Panel Size: 75W

Recommended Battery Size: 50Ah

Combining the two, I used the larger of the recommended solar panel sizes (75W) and rounded it up to 100W, the smallest commonly available panel size. I added the battery sizes together to get 94Ah, again rounding up to a more common size: 100Ah.

So, by my calculations, I will need:

A 100W solar panel kit

A 100Ah battery (at 12V)

A 1000W pure sine wave inverter

Please let me know if my calculations are flawed. I hope my example helps others.

Rich