Full Report! How To Calculate Your Solar Energy Needs

So you want the facts on just how much a solar energy system will cost to install and maintain. Well, the good news is, once installed, solar panel systems require very little effort to maintain.

First of all, we need to determine the size of the photovoltaic solar energy system you will need.

Begin by determining your current electrical usage. Take into account your current peak seasonal usage — and plan ahead. A well-maintained solar system lasts well over 20 years, and you will want to make sure it is robust enough to handle future life changes (such as additional family members).

Now, keep in mind, with a home solar system every watt is precious. Basically, if you have fewer energy needs, you will be able to use a smaller (and thereby less expensive!) solar installation. This may well be the time when you wish to make some changes to more energy efficient appliances and low-energy light bulbs.  (Of course, those are items you can change now regardless of your future solar plans)

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1. Calculate  your current energy usage

So you are looking at the highest energy bill from the last year and trying to figure out where to start. Here’s what you need: Kilowatt-Hours-Per-Day (kWh/day).

Don’t see that on your bill? Thankfully, the math for this is simple. Take the total Kilowatt-hours used that month, and divide it by the number of days in that billing period.  (i.e. 30 days).

Now you have your kWh/day calculation

(For an even more accurate measurement, try adding up your Kilowatt-hours used for the entire year and dividing it by 365)

2. Calculate your Sun

Now, pull out your  insolation (amount of sunlight) map. Like this US insolation map:

This map gives you an average number of hours per day that you can expect to experience usable sunlight.   So if you live in Florida, expect about 5 hours, on average of sunlight per day

(Insolation map for US during month of January. Source: NREL)

3. Calculate your solar needs

So, if you live in Florida, and you needed 25 kWh/day of energy, your initial calculation would be 25(kWh/day) / 5 hours of sun = 5kW system

But not so fast!

Solar cells are only about 20% efficient. So you need to multiply your calculation by a factor of 1.25 to compensate for that.

5kW x 1.25  = 6.25 kW system ( or 6,250 watts)

So an average home in Florida would need a 6250 watt system.

4. The Costs for a Solar Panel system (Solar Panel Costs)

If you surf the internet you will find estimates ranging from $6-12 per watt for complete solar systems.  Solar systems require not only the panels, but battery systems for storing the energy and inverters to convert the energy from battery power to home-energy current.  If you are planning on using one of the popular home energy loans out there, or receiving any government rebates for your installation, you will need to plan on the higher end of the spectrum as all of the equipment must be installed by a

So for our home in Florida, installed by a certified contractor, you could expect to pay anywhere from $37,500-$75,000 for the complete system. (Probably not the pocket change you were helping to shell out) Keep in mind, this is for a 25 kW/day system. That’s a large system. Swap out your lightbulbs for some of the amazing new low-energy fluorescent or LED bulbs and add some energy efficient appliances, and you can easily halve that number.  Or, invest in a Do-It-Yourself manual on solar panel construction and you could literally pay pennies per watt to install your solar energy system instead of $6-$12.

5. The Benefits of a Solar Panel system (Solar Panel Savings)

Rates for electricity ranges anywhere from 7 cents on up to 50 cents per Kilowatt-Hour.  So let’s assume our home in Florida is paying 15 cents per Kilowatt-Hour. How long will it take our system to pay back it’s initial investment?

Our house in Florida is using about 9,125 kWh per year. That’s about $1,369 per year.   That means we could expect around 27 years to recoup the initial investment.

Which is why many people are looking for ways to save money on Solar installation. Do-it-yourself guides or researching contractors to find the best prices and the best rebates are critical to creating a system that is truly freeing

One of the benefits of a Do-It-Yourself approach is that you can create your solar system in stages, slowly transitioning from grid power to solar savings as money and time allow. That’s also why many people are taking a holistic approach to their energy needs, combining wind and solar to better meet their needs and save them money.  We recommend this  insightful series of e-books and CD’s that shows you not only how to save thousands of dollars in you Solar construction project, but gives you step by step instructions on building your own system.

That’s more money in your pocket, and so easy a high-schooler can do it.