What size off grid system do I need
Choosing the correct size off-grid solar system is one of the most important decisions when planning an independent power supply. Whether you’re powering a shed, workshop, cabin, boat, campervan or an off-grid home, the right system size depends on how much electricity you use each day, not simply the size of the solar panel.
A properly designed off-grid system will generate enough energy during daylight hours to recharge the batteries while providing sufficient stored power for use at night and during periods of poor weather.
Start by Calculating Your Daily Energy Usage
The first step is to work out how much electricity you need each day. List every appliance you plan to use and estimate how many hours it will operate.
For example:
| Appliance | Power | Hours Used | Daily Energy |
|---|---|---|---|
| LED Lights | 20W | 5 | 100Wh |
| Laptop | 60W | 4 | 240Wh |
| Small Fridge | 60W | 10 | 600Wh |
| Phone Charger | 10W | 3 | 30Wh |
Total daily energy requirement = 970Wh
This figure becomes the basis for sizing your entire off-grid solar system. The next step is selecting the correct solar battery capacity.
Understanding How an Off-Grid Solar System Works
Unlike a grid-connected solar PV system, an off-grid solar system must generate and store all of the electricity you need. Every unit of energy used during the day or at night must first be produced by your solar panels and stored within your battery bank.
A simple way to understand this is to think about the amount of energy your solar panels can generate during daylight hours. For example, a 100W solar panel receiving around 5 hours of effective sunshine could generate approximately 500Wh of electricity in a day. That energy is then stored in your battery, ready to power your appliances when required.
This simple calculation forms the basis of every off-grid system design. Once you know how much electricity your appliances use each day, you can calculate:
- The size of solar panel required.
- The battery capacity needed.
- The correct charge controller.
- The appropriate inverter size.
Designing the system around your daily energy requirements helps ensure reliable performance throughout the year while avoiding undersized batteries or unnecessarily large systems.
Typical Off-Grid System Sizes
| Application | Typical Solar Array | Battery |
|---|---|---|
| Shed | 100–200W | 100Ah LiFePO₄ |
| Garden Office | 400–600W | 200Ah LiFePO₄ |
| Cabin | 800–1,500W | 300–600Ah |
| Off-Grid Home | Custom Designed | Custom Battery Bank |
Choosing the Right Solar Panel Size
Your solar panels must generate enough electricity to replace the energy used each day while also charging your battery bank. Choosing the correct solar panel size and type is essential to ensure reliable performance throughout the year.
In the UK, the amount of energy produced varies throughout the year, so systems intended for year-round use usually require larger solar arrays than those used only during the summer.
Choosing the Correct Battery Capacity
The battery bank stores energy generated during the day so it can be used when there is little or no sunlight.
A battery that is too small will discharge quickly, while an oversized battery may add unnecessary cost. Choosing the correct battery capacity is therefore just as important as selecting the right solar panels.
For most modern off-grid installations, LiFePO₄ batteries provide excellent performance, long service life and minimal maintenance.
Every Off-Grid System Is Different
There is no single off-grid system that suits every application.
The correct design depends on factors including:
- What you want to power.
- Your daily electricity consumption.
- Whether the system will be used all year or only seasonally.
- Available roof or ground space for solar panels.
- Your preferred battery voltage (12V, 24V or 48V).
Choosing the Right Equipment
Every off-grid installation is unique, which is why correctly matching the solar panels, battery storage, charge controller and inverter is essential.
At Dragons Breath Solar, we supply complete off-grid solar systems together with all of the individual components needed to build or expand a reliable standalone power system. Whether you need a small battery charging system for a shed or a larger installation for a cabin, workshop or off-grid property, we can help you select compatible equipment that meets your energy requirements.
If you’re unsure what size off-grid solar system you need, our team can advise on the correct combination of solar panels, batteries, charge controllers and inverters for your application.
Frequently Asked Questions
Can I run a fridge from an off-grid solar system
Yes. A correctly sized system with adequate battery storage can comfortably run an energy-efficient refrigerator.
Can off-grid solar work in winter
Yes, but systems designed for year-round use require additional solar capacity and battery storage to compensate for shorter daylight hours.
Can I expand my system later
In many cases, yes. Provided the original system has been designed with expansion in mind, additional solar panels and battery storage can often be added in the future.
Expert Advice
If you’re unsure what size off-grid solar system you need, we’re here to help. Our team can advise on the correct combination of solar panels, batteries, charge controllers and inverters for your application, helping you build a reliable and efficient off-grid power system.
You can also explore our range of Off-Grid Solar Kits, Solar Batteries, Charge Controllers and Inverters, or contact us for tailored guidance.
