Solar Power Home

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 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 - 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.

Now take your average kwH per month and divide that by 30 to get your average kWh per day.

- Let’s use an example: If our monthly energy usage is 800kWh, then the average daily power used is: 800/30 = 26.7 kWh a 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 Total Solar Panel Watt Needs:

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 needed / 5.5hrs of sunlight x 1.25 = 3.045 kW or 3045 Watts a day.

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

3 - The Cost Of The Panels:

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.

- Following on from our example, the solar panels will cost 3045 x 4.85 = $14,768 to only halve our monthly power costs. This excludes the cost of wiring, charge controllers, batteries, inverters, and installation fees.

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.