What size of Solar Power System (Solar Panels) you need for your home?

size of Solar Power SystemAre you planning to buy a solar power panels for your house?  As you know, Solar power panels are getting cheaper day by day and electricity from nonrenewable sources like coal power plant etc. is getting costlier. So it’s best option to opt for solar power plant for your house. It is a good investment also. You can sell the extra unit produced by solar power plant to the state electricity grid and can earn extra money.

Buying the solar panels is a difficult task for an ordinary person until or unless no certain basics about solar energy. So here I prepared a series of articles that will help you to make better decision while buying solar power plant for your home. This series include:

  1. Buying Solar Panel? 5 Point Guide to buy Solar Panels.
  2. What size of Solar Power plant (Solar Panels) you need for your home?
  3. Solar Panel Installation: 5 Must Follow Rules for Maximum Performance.
  4. Solar Panel Price in India (2017)
  5. Subsidy on Solar Panel Systems by various State Governments in India.

And in this article, you will know how to find size of solar PV plant for your home roof-top. For determining the size or solar plants for your house, You need to follow following steps one by one:

Size of Solar Power System required for your Home

1. Calculate the electricity load of your house

Calculating electricity load of your house is not a rocket science. It is a simple task. You just need to know some basics.

  • The first thing you can do is just not down the electric appliances you use on your house and number of hours they are used in a day.
  • Then note down power rating (wattage) of the appliances. Power rating of appliances is often expressed in Watts (W). For example, The power rating of a ceiling fan is about 80 W. It means that the ceiling fan consume 80 W for running one hour.
  • Calculate Watt-hours (Wh) used by appliances in a day by using this formula:

Total energy requirement/day = (Wattage of appliance*No. of appliance units*Hours of working)/1000

You can also find out total Watt-hours (Wh) of common household appliances in the following table:

AppliancesNumberWattage (W)Working hoursEnergy (kWh per day)
CFLs Lights22580.4
LED Bulbs
Ceiling Fans
Refrigerator (170 ltrs)1300123.6

2. Decide size of solar power plant

Considering example given in previous table, the electricity load of your house is 5.6 kWh per day. It means you need a solar power plant of greater than 6 kWh per day, which is quite big.

To reduce the load, you might want to run some high power consumption appliances such as refrigerator on household electricity supply. Avoiding refrigerator on solar power, the power requirement for your household is 2 kWh per day.

Adding a 30% safety margin to this, and assuming the insolation (amount of solar energy available to you which is limited by the amount of sunlight that falls on a solar panel per day) to be 4kWh/m2/day in India, we have

System size = (Energy Requirement*1.3) /insolation level

= 2*1.3/4 = 0.65 Wp

Note: Now you can measure exact amount of solar insolation by android app- ISRO’s Solar Calculator App

  • The App provides solar energy potential (in kWh/m2) at any given location
  • The required location can be keyed in or can be obtained through GPS
  • It also suggests optimum tilt angle for solar PV installation
Solar calculator

Solar calculator App by ISRO

3. Finding number of solar panel required

For a large solar power plant, you must select maximum size panel to reduce the cost. In India, the maximum size of solar panel available is 300 W. Considering this panel, the number of solar panel acquired:

No. of panels = System size/Panel Rating

=(0.65/300)*1000 = 2.16

Therefore the system requires 2.16 panels of 300 Wp at 12V. Or you can opt out for two 300 Wp solar panels and one 20 Wp solar panel.

4. Area required for installation

Typically, a 1 kWp system requires 100-130 sq. ft. so a 2.6 Wp system would occupy about 250-300 sq. ft. un-shaded area.

5. Finding Inverter and Battery size

If you want to install off-grid solar power plant i.e. storing electricity in batteries for use at night, then you need an inverter. The size of the inverter is calculated as follows:

Required Inverter size = Total Wattage of all appliances*(1.45)

= 2.6 * (1.45) = 3.77 kW

Therefore you need an inverter of size 4 kW. You can select batteries matching in power with inverter.

Note: The inverter input voltage (12V, 24V, 36V) must be checked as per output of solar panels. Although output from solar panels can be adjusted for inverter but it is recommended to buy Inverter with High Input DC Voltage like 36V. High voltage will result into less line-loss in electricity cables installed between solar panel output port and the inverter. These solar inverters are also more efficient in comparison to low voltage inverters.

For any questions, please comment below.

What size of Solar Power System (Solar Panels) you need for your home?
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What size of Solar Power System (Solar Panels) you need for your home?
What size of Solar Power System (Solar Panels) you need for your home? Find number of solar panels, Area required for installation, Battery-Inverter Size.
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