Solar Calculator & Installation Guide


Which size solar panel you use depends mainly on how much roof space you have available and how much electricity you plan to use (with solar power). Below are 6 steps to calculate which size solar panels you need for your building.

Step 1: Know Your Electricity Usage

Gather your old electricity bills for the past 12 months. Contact your utility company if you don’t have them and your electricity provider should gladly send you a printout with your past electricity usage. You’re looking for 2 things: (1) your monthly kW/h usage, and (2) your monthly cost.

LIGHTING

 

 

Rating/Wattage (W)

 

No. of Hours of use per day

 

Quantity

 

Consumption per day (kWh)

 

Consumption per month (kWh)

Incandescent Bulb

 

100

 

4

 

1

 

0.40

 

12.00

 

 

 

 

 

 

 

 

 

 

60

 

3

 

1

 

0.18

 

5.40

 

 

 

 

 

 

 

 

 

 

40

 

3

 

1

 

0.12

 

3.60

 

 

 

 

 

 

 

 

 

 

Compact Fluorescent Lamp

 

18

 

3

 

1

 

0.07

 

2.03

 

 

 

 

 

 

 

 

 

 

36

 

3

 

1

 

0.14

 

4.05

 

 

 

 

 

 

 

 

 

 

18

 

3

 

1

 

0.07

 

2.03

 

 

 

 

 

 

 

 

 

 

LED

 

5

 

3

 

1

 

0.02

 

0.45

 

 

 

 

 

 

 

 

 

 

8

 

3

 

1

 

0.02

 

0.72

 

 

 

 

 

 

 

 

 

 

5

 

4

 

1

 

0.02

 

0.60

 

 

 

 

 

 

 

 

 

 

AIR CONDITIONERS

 

 

 

Rating/Wattage (W)

 

No. of Hours of use per day

 

Quantity

 

Consumption per day (kWh)

 

Consumption per month (kWh)

Air Conditioner 1

 

2900

 

6

 

1

 

13.92

 

417.60

 

 

 

 

 

 

 

 

 

 

 

 

Washing Machine/Tumble Dryers/Vaccum Cleaner

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Rating/Wattage (W)

 

No. of Hours of use per WEEK

 

Quantity

 

Consumption per WEEK (kWh)

 

Consumption per month (kWh)

Washing machine

 

1000

 

4

 

1

 

4.00

 

16.00

 

 

 

 

 

 

 

 

 

 

 

Tumble Dryer

 

1300

 

4

 

1

 

5.20

 

20.80

 

 

 

 

 

 

 

 

 

 

 

Vaccum Cleaner

 

650

 

1

 

1

 

0.65

 

2.60

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

OTHER APPLIANCES

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Rating/Wattage (W)

 

No. of Hours of use per day

 

Quantity

 

Consumption per day (kWh)

 

Consumption per month (kWh)

Refrigerator

 

250

 

24

 

1

 

2.00

 

60.00

 

 

 

 

 

 

 

 

 

 

 

Dishwasher

 

1200

 

0.5

 

1

 

0.60

 

18.00

 

 

 

 

 

 

 

 

 

 

 

Electric Iron

 

40

 

2

 

1

 

0.08

 

2.40

 

 

 

 

 

 

 

 

 

 

 

Electric Oven

 

100

 

0.5

 

1

 

0.05

 

1.50

 

 

 

 

 

 

 

 

 

 

 

Microwave

 

60

 

3

 

1

 

0.18

 

5.40

 

 

 

 

 

 

 

 

 

 

Electric Kettle

 

60

 

3

 

1

 

0.18

 

5.40

 

 

 

 

 

 

 

 

 

 

 

Rice Cooker

 

200

 

2

 

1

 

0.40

 

12.00

 

 

 

 

 

 

 

 

 

 

 

Toaster

 

 

200

 

0.25

 

1

 

0.05

 

1.50

 

 

 

 

 

 

 

 

 

 

 

Fan

 

 

350

 

2

 

1

 

0.70

 

21.00

 

 

 

 

 

 

 

 

 

 

 

Electric Water Heater

 

3500

 

0.25

 

1

 

0.88

 

26.25

 

 

 

 

 

 

 

 

 

 

 

Television

 

60

 

2

 

1

 

0.12

 

3.60

 

 

 

 

 

 

 

 

 

 

 

DVD/Hi Fi/Blu-ray

 

40

 

2

 

1

 

0.08

 

2.40

 

 

 

 

 

 

 

 

 

 

 

Vape

 

 

6

 

12

 

2

 

0.14

 

4.32

 

Step 2: Know your Roof Direction

Grab a compass (maybe your car navigation, or check Google Maps) and figure out which way is South. Go outside, look at your roof and see how much roof space is facing South, Southwest, East and West. The more South the better, but West is actually okay.

Roof Direction idea for solar

Roof Direction idea for solar

Step 3: Measure Roof Area

Measure your available roof space facing South, SW, and/or W. There are several ways to do this, but the easiest is just to let an installer give you a free quote. You can also use Google Earth, or simply get out on your roof with measuring tape.

Roof Area estimate

Roof Area estimate

Step 4: Calculate How Many Solar Panels Will Fit

Now that you know how much roof you have available for solar panels and how big of a system you need, you need to determine what size panels you will need to cover your electricity usage while staying within the space you have available.

Determine the number of panels you can fit on your roof by dividing your roof area (maybe 600 sq ft for a 2,000 sq ft home) by 16 square feet (500/ 16 = 31.25). Round down, as you cannot fit partial panels on your roof. So I can fit a maximum of 31 panels on my roof.

250w-300W-SOLAR-PANEL

250w-300W-SOLAR-PANEL

Step 5: Calculate What Size Panels You Need

Now divide the array size (of the solar electric system) you need, by the number of panels you can fit. For example, let’s say you need a 6 kW solar system to cover 90% of your electricity usage and you can fit a maximum of 31 panels on your roof. So 6,000 kW / 31 panels = 193 kW/panel. So to meet your needs, you need to use solar panels rated above 193 kW (PTC)/ panel. This means you’ll probably use panels advertised as 220 kW (STC) or higher.

5kw Solar Power Plant

5kw Solar Power Plant

Step 6: Call us and Get Free Quote for any size of Solar

Next, you can contact us to estimate the cost installing a Solar Power Plant.

Get a free Quotation