Monday, June 1, 2009

How To Work Out Your Home's Solar Panel Watt Requirements

By Tim McDonald

With green living becoming more and more important, many people are starting to install home solar power to supplement their power, and reduce their electric expenses.

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?

Here is a simple 4-step formula to help you calculate your home's solar panel watt requirements and costs:

1 - Calculate Daily Power Used:

Your first step is to work out the average daily kilowatt hours (kWh) used. This can be done by looking back at your last twelve months power bills, and see how much power used per month, and get the monthly average. This will give you a better estimate of your average power needs by eliminating the effect of the seasons. It is calculated by adding up all 12 bills and dividing the total power used by 12. If you do not have the the past year's bills, then look at your most recent one.

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

- 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 - Work Out Your Solar Panel Watt Requirements:

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.

Now take the average daily kWh calculation and divide that by the number of daily usable sunlight hours, then multiply that by 1.25 (to take into account the wasted energy from wiring, charge controllers. batteries, and inverters).

- Continuing from our example: Our solar panel watt needs equal:

13.4 kWh / 5.5hrs x 1.25 = 3.045 kW or 3045 Watts per day.

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

3 - Calculate Solar Panel Watt Costs:

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.

- Continuing with the same example, the cost of the solar panels will be 3045 x 4.85 = $14,768. This is only to reduce our power bill by 50%, and it is before the costs of charge controllers, inverters, batteries, and electricians.

4 - Subtract Tax Rebates And Subsidies:

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.

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.

- 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.

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.

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