What Size Solar Power System Do I Need for My Shed?
Most homeowners have sheds where they do most of their rough work, personal projects, and other tasks. If you want to go off-grid with your shed, the best way is to power the load with alternative energy sources like solar power.
Considering that most people work on metal wood and perform similar tasks at their sheds, the average shed might need a solar installation of 2.7 kWp DC to be fully powered and autonomous from the energy delivered to the home.
If you are looking to power your shed with solar energy, this article is for you. Here we analyse the estimated load of a shed, and we teach you how to make the detailed calculations to size a PV system to power your shed.
Learn about the best solar panel options for your home.
How to Size the PV System for Your Shed?
If you are looking to power your shed with solar energy, this article is for you. Here we analyze the estimated load of a shed, and we teach you how to make the detailed calculations to size a PV system to power your shed.
When looking to power a shed with solar energy, several calculations are required to estimate how many solar panels you will need. In this section, we make the calculations by considering essential aspects like the load of the shed and location of the home, calculating the PV system required to power the shed.
While our study case might not adapt precisely to your shed and power usage parameters, it will work as a guideline so you can make these calculations considering your particular needs.
On top of calculating the solar panel installation required, we will also add a solar energy storage system to provide the shed with autonomy to achieve solar self-consumption, which is the same as having an off-grid solar system for your shed.
Calculating the Load or Power Demand From the Shed
You can estimate the required power using your electricity bill for a home, but this is not the same case for a shed. This means that to estimate the load of the shed, we have to calculate the power demand of the equipment installed on it.
Power consumption for appliances according to Consumer Guide to Home and the General Electric website – Source: Inbound Solar
The power consumption guide for appliances (figure 1) lists the most commonly used electronics and tools for a home. At the right of each appliance, the list states the power consumed by the appliance each hour. To calculate the estimated consumption for a shed, we will assume a full day of work of 9 hours (10:00 to 21:00) while powering tools for 1 hour at a time and factoring in the lighting system.
| Item | Power (W) | Daily usage hours (h) | Power consumed (Wh) |
| 4 x LED Bulb – 100 Watt equivalent | 92W (23W each bulb) | 9 | 920 |
| Drill – 1/2” | 750W | 3 | 2,250 |
| Drill – 1” | 1,000W | 1 | 1,000 |
| Circular Saw 8-1/4” | 1,400W | 1 | 1,400 |
| Disc Sander 9” | 1,200W | 1 | 1,200 |
| Band Saw – 14” | 1,100W | 2 | 2,200 |
| Vacuum | 1,000W | 1 | 1,000 |
| Total consumption ( Wh per day) | 9,970 |
With this calculation, we estimate that during a 9 hour day of work at the shed, we consume around 9,970 Wh or 9.97 kWh, which will be the number used to calculate the size of the PV system. Perform this calculation with the regular power usage at your shed to get the size of the load required for your calculations.
Factoring your Location
One crucial factor to consider when calculating the size of a PV system for your shed is your location. Some states perceive more or less solar exposure than others, causing sheds in different areas to require more or less solar panels to generate the same amount of power.
When wondering how much energy does a solar panel produce, it is vital to consider the Peak Sun Hours (HSP), which is the equivalent of solar radiation of 1000 W/m2, the maximum irradiance perceived on the surface of the earth that makes a PV system produce power to its total capacity. Depending on the amount of HSP, the power output of the PV system varies.
Map of Solar Irradiation in the U.S. – Source: SolarGIS
The figure above shows the irradiation levels perceived all around the U.S. Some states might perceive up to 6 or 8 HSP, while others perceive around 4 HSP. You can find the specific HSP at your location by using the National Renewable Energy Laboratory (NREL) site. In our calculations, we will consider 6.25 HSP, which is the medium between the 5 – 7.5 kWh/day perceived in California.
Calculating the Number of Solar Panels at the PV System
Considering the daily power consumption of the shed (kWh) and the HSP in California, we can calculate the DC power required for the PV system. To do this, we divide the daily energy consumed by the shed, the HSP, and introduce a derating factor of 0.6, which is associated with PV losses for an off-grid system. We will use this formula:
After making the calculation considering our particular case study, we require a system with a solar power DC generation capacity of 2.658 kWp to power the shed. The following analysis shows us the number of modules used for the PV system powering the shed.
We will use the CS3K-300P KuPower (Figure 4) 300-watt solar panel for our study case. The formula two used for calculating the number of panels divides the DC Power of the PV system for the shed by the capacity of the PV module:
When making the calculation, dividing the 2.658 kWp of the system by the 300W capacity of each solar panel, we get that to power the shed; we need 8.8 PV modules so that we will use a PV system with 9 of these PV modules for a total DC capacity of 2.7 kWp.
Remember that surge power requirements must be provided for the tools to work. However, this will depend mainly on the battery bank power rating capabilities, but that’s another story.
Conclusion
Calculating the number of panels required for the PV system of your shed is extremely easy and you only need to use the two formulas featured in the article. When calculating the PV system, adapt the power consumption to the load of your shed and consider the HSP regarding the location of your home, this will deliver the most accurate results for your system.
Installing a battery system is also necessary to complete the off-grid system. Solar lithium or deep cycle battery banks, are a good solution for this purpose.
If you are not sure about the available space on the roof of your shed, you can use a highly efficient online tool like the PVWatts web app designed by NREL. Here you can calculate the required space to install a PV system for your shed, and you can even calculate how much power you can install on the whole roof. Keep in mind however, that this tool is oriented to grid-tied PV systems only, so you may need some extra solar power.
Frequently Asked Questions
Where Should I Install the Solar Equipment for the Shed?
There are a few different types of solar panels, inverters, solar charge controllers, batteries, and other components, with each of them having additional Ingress Protection (IP) ratings. If you do not have enough space inside your shed to install the required solar equipment of the PV system, you can look for solar components designed with an IP rating for outdoor usage; we recommend an IP rating of 65 or above.
In the case of batteries, they might not be protected against water like some PV system components, but you can use battery boxes that can be installed outdoors or even underground. However, keep in mind that the batteries must be either lithium or AGM/Gel type models in underground scenarios.
Which Factors Can Affect the Power Production of My PV System?
The power output of the PV system installed at your shed can be affected by many factors like the solar panel efficiency, exposure to direct sunlight, size of the PV system, and atmospheric elements. PV systems work best when the solar panels are fully exposed to direct sunlight without partial shading and optimal solar radiation. Consider this regarding your expectations for the power generation of the system.
Is Your Shed Suitable for Solar Panel Installation?
One limitation for installing PV systems on a shed is the structural support, explicitly referring to how much weight the shed roof can handle. For instance, the CS1U-400MS HiDM PV module weights 51.6 lbs. This means that the top for the calculated PV system needs to withstand at least a weight of 361.2 lbs. plus the weight for the racks used to install the modules.
