How Many Solar Panels Does It Take to Make One Kilowatt? Calculating
the Number of Panels Required for Your Home Energy Needs
Converting to solar power is an
environmentally-friendly option that has been getting more attention
in recent years. But how many solar panels would a residential home
need, and how
many solar panels does it take to make one kilowatt?
Everyone’s lifestyle is different and so is the amount of energy
they consume. Consumption depends on the type of appliances you own
and how often they’re used. So when it comes to ‘getting off the
grid’, you need to determine a realistic energy consumption that
does not impact your needs or lifestyle.
A solar array is an interconnected system of smaller photovoltaic
(PV) modules called PV cells, or solar
cells. These cells, when connected in series (one after another),
can charge a bank of batteries that will store the energy until
needed. A device called an inverter is placed between the batteries
and the final load, converting this energy into electricity that
can be used to power your lights and appliances.
Each solar array has a specific rating. Some are 50 W, 80 W or
120 W which means how much power it can output under ideal sunny
conditions. As you can see, the panels are measured in Watts yet
most appliances require kiloWatts. Therefore, a number of these
solar arrays are required in order to meet a typical daily energy
Before we start get to the number of solar panels required,
How much power do you need?
Electrical power is measured in Watts and energy consumption
is measured in kiloWatt hours (kWh). A kiloWatt hour is simply:
The amount of electricity used (1000 Watts = 1 kiloWatts), in kiloWatts
The number of hours the energy is used.
Usually the calculation states the time period such as one
day, one month or one year.
For example: if a 100 W light bulb is on for 10 hours a day then:
100/1000 (kilowatt) x 10 (hours) = 1 kWh per day.
In one month, that same 100 W light bulb, turned on for 10 hours a
day will consume:
100/1000 (kiloWatt) x 10 (hours) x 30 days = 30 kWh hours per month.
Your electrical bill will usually show how many kWh all of your
electrical devices used over the last billing period (usually around
Determine Your Energy Requirements
Before converting to solar power, look at your electricity bills
from the last year, and determine your energy usage. Some of us will
use more energy in the summer when the air-conditioner is running.
Others, who live in colder climates, will use more electricity in
the winter, when the nights are cold and long. Make a good estimate
at how much power you’ll need per day. If this is for a new
installation, such as a cottage, then here are some average numbers
to get you started**:
- 16 W bulb (on 10 hours) – 4.8 kWh/month (57.6 kWh/year)
- 100 W bulb (on 10 hours) – 30 kWh/month (360 kWh/year)
- Refrigerator – 36.7 kWh/month (440 kWh/year)
- Dishwasher – 41 kWh/month (492 kWh/year)
- Clothes Washer – 24.9 kWh/month (299 kWh/year)
- Electric Clothes Dryer – 74.7 kWh/month (896 kWh/year)
- Stove & Oven (self-cleaning) – 61.25 kWh/month (735 kWh/year)
** Source: Natural Resources Canada
Will solar power work in my location?
Solar panels will work anywhere there is sun; however, some
locations are better than others. Here are some of the more important
factors you need to take into account:
- Location. Southern locations receive more direct sunlight than northern
- Season. In the northern hemisphere, daylight hours are longer in summer
and, once the batteries are fully charged, the excess electricity will be
wasted. In winter, the days are shorter and there may not be enough sunlight
to recharge the batteries for the night-time requirements.
- Climate. Solar arrays are most efficient in bright, direct sunlight and
can be reduced by 50% if the sky is overcast. If snow collects on the panel,
the array will stop produce electricity until the snow melts or it is manually
- Obstacles. Anything that blocks sunlight from falling on the panels will
reduce the efficiency of the arrays. This includes shadows, leaves, dust
and other debris. The panels can quickly become inefficient when obstructed
from full, direct sunlight.
How many solar arrays will I need?
The answer to this question depends on your lifestyle and energy
consumption. As a rough calculation, if you require 3.85 kWh per day,
then you’ll require the following number of solar panels:
3.85 kWh (per day) divided by 7 hours of sunlight (per day)
= 0.55 kW from the solar array
If you have a 120 W panel, one of the largest units available today, then you’ll need:
0.55 (kW) divided by 120/1000 (kW)
= 4.6 panels
This is a rough calculation but it shows that under ideal conditions,
you’ll need more than one solar panel to meet a typical lifestyle. This is
assuming the following:
- Your roof is large enough to accommodate 5 panels (since you can't
really have "4.6" panels).
- The panels receive direct sunlight for at least 7 hours a day.
- There are no obstacles in front of the arrays.
- The panels are kept clean.
It's hard to know how many solar panels you would need, as it depends
on so many factors. However, the above calculations can provide you with
a good starting point to see if solar power is a viable option for your
home energy needs.