How To Calculate Your Solar Power Needs And Costs
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 before you install a home solar power system, how many panel will you need in order to say reduce your utilities by half? And how much will you have to invest in the system?
This is the process we followed, when calculating our home’s solar power needs and the investment required.
1 - How Much Power Do You Use Per Day?:
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.
Now take your average monthly usage and divide it by 30 to work out your average daily power consumption
- So for example: If you have a monthly power consumption of 800 kWh, then your daily amount is 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 The Total Wattage Of Solar Power Needed:
To do this, you first need to determine how many usable hours of sunlight your area receives per day. This is where a solar insolation map comes in handy - you can view one from our original article on our website.
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 indicates that our home solar power system must have the minimum capacity to produce 3045 Watts of power.
3 - How Much Will This Power Cost You?:
Now you you need to calculate how much these solar panels will cost you. At the moment $4.85 per Watt is the highest average cost in the United States.
- 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 - Offset Tax Credits And Rebates:
Before we jump the gun and think it will cost us at least $14,768 for 3045 Watts of solar panel watt power, we need to take tax incentives and rebates in account.
With the new renewable energy tax credits going into effect from January 1, 2009, and state-side rebates from states such as New York, Connecticut, New Jersey or California, our solar installation costs will be much lower than expected.
- Using the same example: For a Californian to buy the solar panels, they would receive a state tax rebate of 20% of the cost, and a federal tax subsidy of 40% of the remainder. So, the investment in the solar panels would only be:
$14,768 - $14,768 x (20%) - $14,768 x (1 - 20%) x 40% = $7,089.
A word of warning: The formula outlined here will give a rough estimate of what you can expect to pay for your solar panel watt needs. Obviously the costs will differ with regard to special offers, the state you reside in and the contractor you use to install the system.
However, from the example, you can see that for Californian to reduce their power bill by half, they would have to buy $14,768 worth of solar panels, costing them $7089 after rebates. A cheaper option would be to learn to source affordable and even free solar cells, and build your own solar panels. This can be done by following a relatively inexpensive step-by-step solar power manual, such as Earth4Energy.
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