How Much Solar Power Do I Need for My Shed?

For many homeowners, their shed is valuable storage, a workspace for projects, or even a quiet retreat. Powering these structures with solar energy is becoming an increasingly popular option, but determining the right amount of solar power for a shed can be tricky. This article guides readers through the process of calculating their shed’s energy needs, selecting appropriate solar equipment, and setting up an efficient off-grid system.

How Much Solar Power Do I Need for My Shed?

For the average shed, it would need around 2.7 kilowatt peak (kWp) direct current (DC). Kilowatt peak, or power DC (kWp), refers to the peak output of the solar power system. If a solar panel has a peak power of 4kWp, the solar panel will produce 4kWp over an hour when working at max capacity.

However, those who use their shed for storage will need much less power than those who use the space as a workshop. 

To determine how much solar power your shed requires and to identify the best system for your needs, you need to do a bit of math, which I explained below.

Calculating Your Shed’s Power Demand

To determine how much power your shed will need, homeowners should list all the electrical devices they plan to use and estimate how long each will run daily. Those who use their shed for storage will need much less power than those who use the space as a workshop.

Here’s an example of what this calculation might look like for a typical workshop shed for nine hours of use:

In this example, the total daily energy consumption is approximately 9,970 Wh or 9.97 kWh.

Factoring in Your Location

The amount of sunlight a location receives plays a role in determining the size of a solar power system. This factor is measured in “peak sun hours,” which represents the equivalent hours of full sun intensity a location receives daily. The more sun an area gets, the higher the solar panel output.

Peak sun hours vary significantly across different regions. For instance, sunny California can receive between 5 to 7.5 peak sun hours per day, while New York sees 4 to 4.5 peak sun hours each day. You can learn more about your area’s sunlight on the National Renewable Energy Laboratory (NREL) website.

For these example calculations, I’ll use California and go with an average of 6.25 peak sun hours, right in the middle of 5 and 7.5.

Sizing Your Solar Panel System

With the daily energy consumption and peak sun hours determined, it’s possible to calculate the size of the solar panel system needed for a shed. For this calculation, I have to introduce a derating factor of 0.6, which is associated with photovoltaic (PV) losses for an off-grid system.

Then, I divide the daily energy consumed by the shed by the peak sun hours and the derating factor.

The formula looks like this: Power DC (kWp) = (Daily Energy Consumption) / (Peak Sun Hours x Derating Factor). For my example shed, the calculations would be: DC Power = 9.97 kWh / (6.25 peak sun hours x 0.6) = 2.658 kWp.

Here’s a look at the formula:

In this case, I would require a system with a solar power DC generation capacity of 2.658 kWp to power my shed.

Determining the Number of Solar Panels

Once the required DC power is known, you have to select a system and how much energy that system’s solar panels produce to determine how many solar panels you’ll need. For this example, I selected a system that has 300-watt (W) solar panels, which converts to 0.3 kW.

The formula required is: Number of panels = (power DC (kWp) / kW). For my example, the calculation would be: 2.658 kWp / 0.3 kW = 8.86 panels. You can also see it here:

Rounding up, this shed would require nine 300 W solar panels for a total capacity of 2.7 kWp.

How to Select the Right Solar Power System

Once you know a bit about the energy your shed requires, you can start thinking about which solar energy system you’d like to purchase. Here are a few factors to keep in mind when selecting your system:

Solar Panels

When selecting solar panels, keep the calculations and your results in mind. Your solar panels’ output will have to match the load demand. Going with a solar array slightly larger than your average daily consumption can account for cloudy days and seasonal variations. It can also help in the event you need more power at a later date.

Panels vary in efficiency, durability, cost, and warranty coverage. High-efficiency panels can cost more up-front, but they can provide better performance in limited space. For sheds, monocrystalline panels often offer the best balance of efficiency and cost.

Battery Storage System

A battery storage system helps power your shed in case there isn’t enough sunlight at any given point. Lithium-ion batteries are popular thanks to their long life span, high efficiency, and low maintenance requirements. Deep-cycle lead-acid batteries can be a cost-effective option.

Smart controllers for the battery can also improve overall efficiency. They manage power distribution and optimize the charging process. As a result, the battery won’t be overcharged, which could shorten the battery’s lifetime.

Inverters

Inverters convert the DC power generated by solar panels into the alternating current (AC) power used by most tools and appliances. A pure sine wave inverter is ideal for sheds as it’s compatible with sensitive electronics.

Structural Considerations

If you’re installing the solar panels on your shed’s roof, it needs to be able to support the additional weight. For example, if each panel weighs about 50 pounds, a system with nine panels would add approximately 450 pounds to the roof, plus the weight of mounting hardware. 

You also need to consider the available roof space and whether it can accommodate the number of panels you need. If you’re unsure, NREL’s web app, PVWatts, can help you with the calculations.

For better performance, solar panels should be installed at an angle equal to the shed’s latitude and facing south in the Northern Hemisphere. There should be no shading, which could affect the system’s efficiency.

How Can I Make My Shed’s Solar Power System More Efficient?

There are a few different ways homeowners can improve the performance of their shed’s solar power system, including:

• Perform ongoing maintenance. Periodically inspect the solar panels for dirt, debris, or damage. Clean the panels gently with water and a soft brush if necessary. Make sure battery connections are secure and check them for corrosion and damage.
• Monitor the system’s performance. Simple monitoring systems can identify issues early and help you improve its overall efficiency.
• Adjust for the seasons. In some geographical locations, adjusting the tilt angle of the solar panels seasonally can improve efficiency. To maximize energy production, increase the tilt angle in the winter and decrease it in the summer.
• Use energy-efficient equipment. Energy-efficient equipment, such as LED lighting and appliances with low standby power usage, reduces the shed’s energy consumption, which then improves the efficiency of the power system. 
• Install hybrid systems. Wind energy can provide additional power if the shed is located in a windy area, especially during periods when sunlight is insufficient. For sheds that need hot water, installing a solar water heater can reduce the demand on the solar energy system.

Conclusion

By carefully assessing power needs and considering local conditions, homeowners can better understand their shed’s energy requirements. If you’re ever unsure about how much energy your shed needs, reaching out to a professional solar panel installer can help you determine the best system for your goals.