Solar System Sizing and ROI Calculator

A PERSONALISED APPROACH

There are many things to take into consideration when calculating the best size system for your home or business. The best size system will usually depend on your expectations. At Commercial Utility Solutions we prefer to take a personalised approach with our customers. We understand the importance of asking a variety of questions to ensure the system we recommend has the best chance of meeting your expectations.

In saying that, the following calculator will guide you to a generalisation of a system size that should be approximately appropriate for you. It is partially personalised as it takes your location and usage habits into consideration, however there are also many generalisations which is why we strongly encourage you to contact us for a discussion prior to making any decisions. There may also be options suitable for you that the calculator does not accommodate for, such as a battery solution.

YOUR CURRENT SITUATION

First of all, to analyse your current situation we will need a little bit of information from you which can all be located on your most recent power bill.

Total amount paid on your last power bill:	$
Electricity rate per kilowatt hour including GST:	$ per kWh
Number of billing days:	days
Total kilowatt hours of electricity used for the period: kWh	kWh

Your daily average cost of electricity is
$ per day

Your daily average kWh usage is
kWh per day

SYSTEM SIZING ANALYSIS

Now tell us a little bit about how you use your power and where you live. This will allow us to determine your areas average daily sunlight and also allow us to understand how much of your power is used during the day when your solar system is producing power.

What percentage of your power do you use during daylight hours:
Select solar irradiation hours based on nearest capital city or use Aussie map and select a number based on your location:
Choose system quality for purchase cost estimate

Click to enlarge

Estimated kWh consumption
offsettable by solar system
kWh

Average peak sunlight hours
based on location
hours

Recommended system size
to offset daytime consumption
kW

Estimated cost of installed
solar PV system after rebates
$

HOW MUCH YOU COULD SAVE

So now that we have matched a system size with your daytime usage habits we can analyse how much money you could possibly save by installing the solar system. Then we can divide the annual savings into the estimated cost of your system to calculate your annual return on the money invested into the solar PV system. To calculate this, we will be using your current electricity rate you gave us in the first section, however, since electricity prices seem to be always increasing, the savings in the future will likely be even greater than what is shown here as time goes on and the electricity rates increase. If you feel the estimated cost of installed solar PV system price above is inaccurate, you can adjust the system price using the drop-down menu here.

Choose period to analyse:

Electricity savings over period selected
$

Annual ROI
%

COMPARE DOING NOTHING TO MAKING THE SWITCH TO SOLAR

Here we will take a look at what your electricity expense will be over a period of time selected by you in two scenarios. First of all, how much will you spend on your electricity account if you do nothing and continue to pay for electricity the way you currently are based on the information you provided in the ‘your current situation’ section. And secondly, how much will you spend over this same period of time if you installed the recommended solar system.

This part of the calculator allows you to specify an expected annual rate of increase for the kWh rate charged to you by your electricity provider.

You will note that due to the upfront cost of the solar system, in the short term the solar scenario is worse off, however, over the long term is when the benefits of the solar installed scenario really become magnified. Like many investments, you have an upfront expense from acquiring the asset, then you receive income from the asset – for solar this income comes in the form of savings on your electricity account – then you have a break-even point, from there you begin to make a net profit. Referring to solar PV installs, this is when the savings on your electricity account exceed the cost of the solar PV installation – this usually occurs between 3-8 years after installation depending on your situation.

Years to assess:
Annual rate of increase to electricity charges

Do Nothing
$

Solar Installed
$

Net benefit
$

USING A LOAN FOR PAYMENT?

The above analysis assumes you paid for the solar PV system with money from the bank and does not take into consideration any costs associated with financing. Since paying for a solar system with a loan is actually the most common method of payment, here we will look at how things change when taking associated financing costs into consideration.

Inputs
Deposit (Optional):	$
Annual loan interest rate:	%
Choose a loan repayment frequency:
Term of loan in years:

Outputs
Amount to be financed:	$
Loan repayments per period	$
Savings per period	$
Net benefit per period	$
ROI – Annual (including cost of finance – interest and principal repayments)	%
NOTE: after the loan term concludes, the ROI increases to the higher excluding finance ROI amount of:	%

OTHER THINGS TO CONSIDER

The system price estimate within the calculator is very general and mid-range. Depending on your appetite for quality and brand will obviously vary this value. Also adding bells and whistles such as electricity monitoring technology and interfaces, which we strongly recommend, can also increase the upfront price.

In the past when there were government funded feed-in tariff incentives, it often made financial sense to oversize your system, however, since the feed-in tariff is now relatively low and no longer incentivised by government it rarely makes sense to buy an over-sized system for the purpose of feed-in tariff credit.

Other things that are not assessed in the calculator include how much space you have on your roof to accommodate the system and if your available roof space has the best orientation and tilt to maximise your solar generation. The best roof orientation and tilt can also vary depending your situation and expectations, for example, if you want to offset time-of-use metering, then facing your array NNW and having a greater tilt angle for the array could offset more peak energy use, as this design style can optimise your system to make more of the evening sun. This is why again, we encourage you to contact Commercial Utility Solutions for your personalised free quote.

DISCLAIMER

A great amount of care has been taken to ensure the accuracy of the information provided by this calculator, however, it is for general information only and should not be acted on before speaking with a Commercial Utility Solutions solar expert. Click here for the Commercial Utility Solutions disclaimer.

Average peak sunlight hours sourced from: http://www.yourhome.gov.au/energy/photovoltaic-systems