# System and Inverter size

How big, and how much will this electrical system cost?

To get an idea you need to find out the electricity you will consume each day.  To do that gather together every item you expect to power.

You will need to calculate your usage in Amp Hours (Ah).

Amp Hours = Current in amperes x Time in hours

Current:  the amount of electrons flowing in the wire.  The unit is Ampere.

Time:  Some items will not be on very long.  For example, if you have a hot water heater it will be on for about 15 minutes to heat the water.  It won’t be on all day long!

There are many calculators available online to do these calculations.  The math is easy.  The difficult part is getting all the appliances together to get the information!

You will only get an estimate with any of these calculators.  Remember you energy production and usage will vary with the seasons.  In the summer you will use more electricity to keep your refrigerator cold.  In the winter you will not produce as much electricity from your solar panels since the sunlight days are shorter, and they may be covered with snow.

The key is to calculate what is the maximum power that you will need at any given time. To find out, add the power of each device you plan on using simultaneously.

You need to select and inverter that will handle your simultaneous power usage.

For example, I have a 4 gallon hot water heater that is 1500 watts.   I do not expect to use that at the same time I use the insta-pot which is 1200 watts.  But if I did use them at the same time, that would be 2700 watts.  I would need a 3000 watt inverter.

I can go with a smaller inverter, but went with a 3000 watt.  Why?  To future proof my build.  My needs may expand in the future.  Spending a little more money now is the frugal thing to do.  Otherwise if I find out later that I needed a larger inverting I would need to go to the expense again to buy a larger …..