Calculating Your Solar Power Requirements
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 – 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
- 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.
- Now if you want to only halve your power bill then you need to produce 26.7 / 2 = 13.4 kWh of solar panel watt power per day.
2 – Calculate Total Solar Panel Watt Needs:
To work this out you are first going to look at an insolation map to see the average usable hours of sunlight your area receives each day. A map is available 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 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 needed / 5.5hrs of sunlight x 1.25 = 3.045 kW or 3045 Watts a day.
This means we need solar panels with the capacity to produce at least 3045 Watts of power.
3 – How Much Will This Power Cost You?:
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 – Subtract Tax Rebates And Subsidies:
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.
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.
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.