The most important factor in determining what size solar system is right for you is to first understand your electricity consumption.  Obviously the higher your consumption the bigger the solar system needed to get that bill down to 0 if not into credit.

But how exactly do we work out the ideal size system for you?

First of all you need to understand how to read your bill correctly, and what all of the different charges actually mean.

Lets break down the main key components of a standard electricity bill then work out the expected solar savings using a 6.66KW solar system installed in Brisbane using the average production of 29KW a day.

Most households will have at least 2 Tariffs.  The main tariff with the highest usage will be your normal power that is on 24/7, this is charged at a higher rate to the other tariffs.

This is the most important reading because this is the usage that will be directly impacted by your solar system and will determine how much power you use vs how much you sell back into the grid.

You can see on this bill, a total of 1493KW was used on the main tariff over 88 days.  This works out to be an average of 16.965Kw a day.

This is the total usage over a 24hr period, in order to work out the expected usage during the hours the solar system will be operational we now need to work out what 70% of this figure is.  (70% is our go to ratio that we have found gives the majority of our customers an accurate estimate for the expected solar savings.)

70% of 16.965 works out to be 11.875KW.

We can now safely assume that 11.875KW of the 29KW a day that is going to be produced will be consumed by the household and the remainder will be sold back into the grid.

So what are the expected solar savings from your solar electricity bill?

In this example you can see that customer is currently paying $0.2772 per KW of power consumed on the main tariff.

Now we have already worked out that 11.875Kw a day will be consumed directly from the solar system instead off pulling this power from the grid.

This means we can expect a saving per day of 11.875   x 0.2772 = $3.29 saved per day

But we must also remember that a 6.66KW system will produce 29KW a day, and this customer is only going to consume 11.875Kw of power.   This means they will have an excess of 17.125KW a day to sell back into the grid and earn credits.

With a 15c Feed in tariff this works to be an income of $2.56 per day combined with the saving of $3.29 that we calculated earlier.

The total solar savings for this customer is therefore $5.85 a day.

This example bill was over an 88 day billing period, we can now times $5.85 x 88 to get the total expected savings calculation of $515.57.  Which as you can see is actually slightly higher than the customer’s current bill.

So what are all these extra numbers and charges then, and why do you need the extra $2.56 a day in credits just to break even at the end of the quarter?

One charge that everyone will have on their energy bill regardless of how many tariffs you have is something called a supply charge.

This is a charge that you will incur every single day regardless of how much power you are consuming.  This means at the very least regardless of your consumption if you want to completely reduce your power bill, you not only have to cover the cost of the power that you consume but you must also sell enough electricity back each day to cover the cost of your supply charge.

The only other charges that you will have on your electricity bill is for other tariffs that you have connected to your house.

This customer only has a total of 2 Tariffs however it is also very common to have 3. The difference between the tariffs is the number of guaranteed hours of electricity that you will be provided from Energex per day.  Usually the only things connected to off peak tariffs will be hot water systems and pool pumps.

On this bill our customer is using a total of 531KW over the 88 day billing period.  Because this is being consumed on the off peak tariff the solar will not have a direct impact on this, instead we must ensure that we generate enough profit from selling the excess power to cover the cost of this consumption.

You can see that the total cost off the off peak tariff usage was only $118.57 for the quarter, and in this example our customer will make a profit of $225 which is enough to cover both the cost of the supply charge and the off peak usage.

As you can see for a standard bill around the $500 range a 6.6Kw system is the perfect size to get rid of your power bill.  If you would like to get into credit every quarter or if you have an even larger bill then this, then we will need to look into a bigger solar solution.

If you would like help working out the perfect size system for your household then give Goodhew Electrical and Solar a call today and have a chat to on of our solar experts.