How to Size a Solar Power System

Investing in a solar is a smart solution for homeowners and business people. Sizing a solar energy system correctly is very important .The latest solar panels and photovoltaic (PV) systems are easy to install, maintain, and operate, with long-term performance and energy savings.

To make the most of your solar energy system, you’ll want to know how to correctly size the system to cover your energy use patterns without over-sizing or under-sizing your solar panel array.

The most common way to determine the size of your system is by actually figuring out exactly how much power your home/business consumes.Then building a solar power system that can handle that load.

Follow these steps to learn how to get a sizing estimate, calculate your solar needs to get the most benefit out of your solar installation.

Estimating of Your Energy Usage

First find out the total power and energy consumption of all loads that need to be supplied by the solar power system.

Follow these steps to determine your home’s average electricity consumption and energy needs.

1.Calculate Your kWh Usage

Gather the kilowatt-hours (kWh) usage from your electric bill.

You’ll want to have full 6 months of usage to be able to look at peaks and valleys in usage over a year. Add up your kWh usage for at least 3 – 6 months and divide by 3 or 6 to figure out your average monthly consumption.

Divide your answer above by 30 to determine your daily kWh usage.

Multiply your household’s hourly energy requirement (kWh above) by the peak sunlight hours for your area to get Kw output. Then divide the kW output by your panel’s efficiency and solar panel watts rating to get the estimated number of solar panels you’ll need for the system.

Most regions of Kenya receive on average 6 hours of peak sunlight and most solar panels have an efficiency of 15%. This is the energy lost through the system. Add that  in the system so that even in the worst case scenario it will still be able to power all your appliances/load.

Let’s look at an example and assume we got 15kWh as our energy requirement per one hour.

The number of solar panels we shall need will be gotten by doing the following calculation

(15 kWh ÷ 6 sun hours) x 1.15 efficiency factor = 2.88 kW DC solar system size. You can round this to the nearest whole number to get 3Kw.

 Using the example above with a 3 kW DC system, you can multiply this number by 1,000 to confirm that you need 3,000 watts of solar panels.

Go ahead and divide this with your solar panels watt rating. For example, let’s say we are using 250 Watts solar panels. This will give us:

3,000 ÷ 250 = 12 panels

This means you’ll need 12 pieces of 250 Watts solar panel to cater for all your energy needs.

The other method for determining your home’s energy usage more accurately, is by finding out how many kWh your appliances would use. Make a list of the power consumption of all the electrical appliances and devices that will be used in your home.Also an estimate of how long each appliance or device is switched-ON using energy each day.

Then multiply the power consumption (in watts) of each device by the number of hours it is on to give you the daily electrical consumption in watt-hours, as shown.

Then the total energy consumption is estimated at around 2000 watt-hours, or 2 kilowatt-hours per day. However, it is better to add a little extra on top, say 10% to 15%. This is to account for losses in the system or the use of an extra electronic device not accounted for. Thus the new estimated value would be:

2000 watt-hours x 1.15 (15% extra) = 2300 watt-hours or 2.3 kWh.

Divide the answer above with 6 hours of sunlight to determine the peak power generated.

2300 watt-hours ÷ 6 hours = 383 watts-peak or 383Wp. This could be rounded off if required to 400Wp.

Determine Number of Solar Panels needed

We now know how much electric power we require on an average day. The rest is to specify the type and number of solar panels that will produce the required power of 2.3 kilowatts or else 2300 watts.

Let’s use a 250 Watts solar panel as we used earlier in our example. Thus the total number of solar panels required will be:

400Wp ÷ 250 = 2 solar panels rounded off to the nearest whole. So this system should be powered by at least 2 modules of 250 Watts solar panel.

Determine size of inverter

The total wattage of all electrical appliances that we listed above was: 120 + 20 + 20 + 70 + 100 + 10 + 40 = 380 Watts. For safety, the inverter should be considered 20-25% bigger. The inverter size should therefore be about 400 Watts or greater.

Read More: How to Calculate the Size of an Inverter for Your Solar Power System

Storage battery sizing

The amount of energy that will be consumed per day as calculated above is 2300. This is the minimum amount of storage capacity we need for one day. Next we need to determine the number of days of battery back-up that we want to have on hand. This is called “Autonomy”.

Days of Autonomy represents the number of cloudy days in a row that might occur and for which the batteries will need to supply energy to the building. A standard number of autonomy days are usually 2 days. Then the total amount of energy required for a minimum of 2 days of storage in the example above that consumes 2000 watt-hours daily is calculated as:

Appliances use 2300 Watt-hours/day, nominal battery voltage = 12 volts, days of autonomy will be 2 days and efficiency = 85%.

Battery capacity = (2300 x 2) ÷ (0.85 x 12) The total ampere-hours required is therefore 450Ah or greater of battery capacity at 12 volts.

Hopefully by now you have some idea of how to size a solar power system for your home or business. These steps in determining the size of the solar system are by no means the only ones, each case is different and there are different ways in sizing solar power systems.

Need Help with Sizing a Solar Energy System?

It’s easier to talk to a solar installer near you who knows how to size a solar system and can walk you through the design process. Once you’re ready, we encourage you to schedule a FREE consultation with us. We will double-check your sizing, find compatible solar products, and ensure the system works within your budget and energy requirement.

Phone Number: 0759493610
Request A Customized Quote: Click here
Email: info@voltmaticenergysolutions.co.ke