With America’s change of government has come a larger interest in people wanting to use solar power at home, to aid global warming and save on their increasing electricity bills.
But when you install solar power, how much do you actually have to generate to say cut your bills by 50%? And what kind of costs will you be looking at?
Here is a simple 4-step formula to help you calculate your home’s solar panel watt requirements and costs:
1 – What Is Your Daily Power Consumption?:
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 if you want to cut your bill by 50%, then the amount of solar power needed is 26.7/2 = 13.4 kWh per day.
2 – Calculate The Total Wattage Of Solar Power Needed:
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.
Once you know your daily sunlight hours, go back to your daily kilowatt hours needed and divide it by the daily sunlight hours, then multiply it by a factor of 1.25 (takes into account energy losses from the solar panel watt wiring, battery , and inverter)
- From our same example, if we lived in California where it gets on average 5.5 hours of usable sunlight per day, the solar panel watt requirements are:
13.4 kWh / 5.5hrs x 1.25 = 3.045 kW or 3045 Watts per day.
This means we need solar panels with the capacity to produce at least 3045 Watts of power.
3 – Calculate Solar Panel Watt Costs:
Next you need to work out how much it will cost to buy solar panels that produce at least 3045 Watts. Currently the highest average cost for solar panels in North America is $4.85 a 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 thinking that your solar power investment is going to be $14,768 to only halve your power bill, you need to subtract any tax rebates and subsidies on offer.
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.
- Let’s use our example: If we were from California we would receive tax rebates of about 20% of the cost, and a federal tax credit of 40% on the remainder. So after rebates and credits, our solar panels would cost us:
$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.
Anyway, from what you can see it would cost us around $7,089 to buy enough solar panels to halve our power bill. We, instead, either get our solar cells at cost or source them for free, and wire up our own solar panels, which obviously saved us a lot of money. The good news is, anyone can learn to find cheap solar cells and make their own solar panel watt power.
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