Easy Formula To Work Out Your Home Solar Power Requirements And Cost

With our current economic melt down and energy prices fluctuating daily, many of us are thinking of installing solar panel power to contribute to our homes’ energy needs, and reduce our power bills.

But how much solar panel watt power do we need to say halve our power bills? And how much will that power cost us to install?

Here is a four step process that you can follow to answer these two vital questions:

1 - Calculate Daily Power Used:

To work out how much power you use on an average daily basis, this is what you have to do: First go back and look at your past 12 months electricity bills. Then work out the average kilowatt hours (kWh) used per month. The reason we do this is because we use different amounts of power throughout the year. The calculation is month 1 + month 2 + month 3 etc… then divide that by 12. If you do not have all the statements, just use last month’s bill.

Then divide your monthly usage by 30 (the average number of days in a month, to get your daily power used.

- Here is an example: Lets say the power used last month was 800 kWh. Your average daily usage would be 800/30 = 26.7 kWh per day.

- So to reduce your electricity bill to half, 26.7/2 = 13.4 kWh of solar power per day is needed.

2 - Calculate Total Solar Panel Watt Needs:

Before you can work this out, you need to find out how many usable hours of sunlight your region gets per day. A simple way to find that out is to have a look at an insolation map - there is one available on our website, where the original article was posted.

Your next step is to take the daily kilowatt hours needed and divide it by the average usable sunlight hours, then multiply that by 1.25 (this is used to take into account the inefficiencies in the solar power system from wiring, charge controllers, batteries, and inverters).

- From the previous example, if you live near California where the average daily usable hours of sunlight is 5.5 hrs, the solar wattage needed is:

13.4 kWh required / 5.5hrs of insolation x 1.25 = 3.045 kW or 3045 Watts daily.

This tells us that our solar panels must be capable of producing at least 3045 Watts of electricity.

3 - Calculate Solar Panel Watt Costs:

This step will help you work out the cost of the solar panels needed to make 3045 Watts of power. At the moment the highest average cost for solar panels in the US is $4.85 per Watt.

- In our example: It will cost us at the most 3045 x 4.85 = $14,768 to install solar panels to halve our power bill. And that’s before wiring, charge controllers, batteries, inverters, and electrician costs.

4 - Take Government Rebates and Credits Into Account:

Before you think you are going to have to fork out at least $14,768 for only 3045 Watt of solar panel power, you need to consider the effect of government subsidies and incentives.

2009’s Federal renewable energy tax credits came into effect from the beginning of the year, and coupled with the state-side incentives in places like Connecticut, California, New York and New Jersey, the cost of the solar power system will be much less.

- Continuing on from our example: If we lived in California, our state tax incentives would be about 20 % of the investment, and the federal rebates 40% of the remaining cost. So, our solar panels would only end up costing us:

$14,768 - $14,768 x (20%) - $14,768 x (1 - 20%) x 40% = $7,089.

Just remember that this formula is basic way for you to get an idea of what home solar power will cost you. Some things could not be factored in - such as the state or country you live in, the special offers of local solar companies and the cost of the other parts (inverters, charge controllers, batteries, installation fees).

But, from our example it would cost a Californian about $7089 to invest in solar panels that can reduce his electricity bill by only 50%. We, on the other hand, know how to source cheaper and even free solar cells, and build our own solar panels, which makes the cost MUCH lower. If you are a DIY fanatic then it would save you a lot of money if your bought a solar power guide that show you how build your own solar panels.