Going green is one of the world’s biggest priorities at the moment. Installing solar panels on your home can help mitigate some of the effects of climate change while saving you money on electricity bills in the long run.
But different households have different energy needs. To figure out how many solar panels you need for 1000 kWh of electricity per month, you will first need to determine the potential solar energy in your location.
After that, you’ll just need to perform a few calculations to determine how many solar panels are necessary.
Let’s get started!
How Many kWh Does a Solar Panel Produce per Month?
The power-generation capabilities of a solar panel depend on its size and the peak sun hours where it’s located.
Most residential solar panels have ratings between 100 to 400 watts, such as the EcoFlow Portable Solar Panels. Assuming you have a 400-watt panel that receives four hours of peak sun hours per day, it can produce up to 1600 watt hours (Wh) of energy per day.
You can convert this to 1.6 kWh daily and multiply it by 30 days to get the monthly output. In this example, a 400-watt solar panel generates approximately 48 kWh monthly.
This estimate assumes a perfectly ideal solar system, which is impossible. Rainy days, dirt and snow, and other environmental factors will impact the performance of your solar array.
What Is the Solar Energy Potential in Your Area?
The power generation of a solar panel depends greatly on the available sunlight in an area. A solar panel in a sunny, desert region will generate far more power than the same panel in a rainy, overcast location.
The solar energy potential is the number of peak sun hours you expect your panels to receive. For example, Phoenix, Arizona, gets an average of about 6 hours of peak sun per day, while cities like Portland and Seattle may only receive around 4 hours per day.
What Affects Solar Panel Output Efficiency?
Unfortunately, solar panels rarely (if ever) gather their full-rated power. Due to temperature, dirt, and other factors, a solar array may lose 10-20% of its efficiency or more.
Let’s explore some factors leading to diminished solar energy production.
Solar panels are usually tested at 77F (25C) to calculate power ratings. This is the temperature at which photovoltaic cells perform their best.
However, conditions in the real world are rarely this perfect. Hot summers and cold winters will decrease the efficiency of solar panels.
You can take steps to minimise the effects of unideal temperatures, such as optimising solar panel installation. In warm regions, you want to create a gap between the roof and the panels to allow cool air to flow. You can also install fans to blow air over the hot panels or circulate cold water near the panels to absorb some of the heat.
Snow is the biggest concern in cold regions. If your area receives heavy snow, you’ll need to install a heating system or manually remove snow after a big storm. Even a partially-covered panel may render the rest of the system largely ineffective.
The angle of the solar panels is also critical for snowy climates, with the optimal tilt being 53 degrees. Snow on top of the panels can prevent them from absorbing direct light. Researchers have estimated as much as 1.6-5.3% annual solar energy loss due to snow.
You want your panels to receive as much sunlight as possible to harness the most power. Dirt and grime build-up can drastically reduce the amount of sunlight that reaches the photovoltaic cells. Rainfall will help keep your panels clean, but that’s rarely enough.
Regularly check the cleanliness of your panels. If you notice any dirt buildup, it’s time to give them a hose-down, at the least. You can also give the panels a full scrub once or twice yearly to keep them in tip-top shape.
Wiring and Inverters
Power loss often occurs due to the other components of a solar system. Long cable runs can result in a slight loss of power, such as the run from the panels to the battery or from the battery to the rest of the house.
It’s also important to remember that solar panels supply power in direct current (DC), but most homes use alternating current (AC). For this reason, a DC to AC inverter is required in most residential setups — utilising these devices results in a slight loss of power.
So, How Big of a Solar System Do I Need for 1000 kWh per Month?
A simple calculation is required to determine the number of solar panels needed to supply 1000 kWh per month:
(Monthly electric usage/monthly peak sun hours) x 1000)/power rating of the panel
1. Monthly Electric Usage
For our sample calculation today, we will assume we want to supply a home that requires at least 1000 kWh of energy per month.
To determine your monthly energy usage, you can look over your past year of electric bills. Find your highest amount of energy used in a month — this is the figure you should use when calculating your solar energy needs. You can also add 5-10% to account for future energy usage increases.
As a comparison, the average American home used about 886 kWh of monthly energy in 2021.
2. Monthly Peak Sun Hours
When determining monthly peak sun hours, you will likely want to use the month with the lowest expected sunlight. This will be a winter month in most locations when the total daylight hours are low. The peak sun hours can vary depending on your region, but around four hours per day is a good average.
For our example, we will assume 120 monthly peak sun hours or about four hours per day.
3. Power Rating of Solar Panels
Most solar systems will use a combination of identical solar panels wired together (either in series or parallel). Solar panels come in all shapes and sizes, from small 10W panels to 1000W behemoths. However, most residential panels will have ratings around 160W to 400W.
The EcoFlow 400W Rigid Solar Panel is a good example of a rating suited for a residential installation. We will use that for our sample calculations.
4. Number of Solar Panels Needed for 1000 kWh
Let’s start plugging our numbers into the equation above.
First, we can divide our monthly electric usage (1000 kWh) by our monthly peak sun hours (120). That gives us 8.333 kW. To convert kilowatts to watts — the unit of power supplied on most solar panel ratings — we’ll multiply by 1000, giving us 8333 watts.
Lastly, we will divide the 8333 watts by the power rating of our chosen panel (400W). It gives us 20.83, or 21 panels when rounded up.
This estimate indicates that we need 21 panels rated at 400 watts to gather enough energy to supply a home with 1000 kWh. That said, you may want to size up a bit more to account for rainy months, power lost to inverters, and other factors.
Now that you know how many panels you need, it’s time to put together the rest of your solar system! Before you know it, you’ll be helping to slow the effects of climate change.
If 21 panels are out of your budget at the moment, consider buying a portable solar generator, like the EcoFlow DELTA Max + 160W solar panel. It provides backup or on-the-road off-grid power. Pairing solar panels with a portable power station can keep you powered in the case of a blackout. You can expand your capacity to ensure a sufficient energy supply to run your home appliances using solar energy when your budget allows.
Whichever route you choose, you’ll be doing your part to make the world a little greener, save on your electricity bills, and reduce your reliance on the ageing power grid over time.