Thinking of going off the grid with solar energy? We’ve created this complete guide to help you!
Off grid living means you have no connection to the electric utility’s distribution network. When you go off-grid, you take on the role of the power company, generating and supplying the power to yourself. A fully functional off-grid solar system comes with four essential components: solar panels, batteries, a charge controller and an inverter. The exact components will vary depending on how much power you need to generate and use for the lifestyle you will have, so your first step is working this out.
Calculate your yield - How much power am I using?
Before choosing your solar components, you will have to estimate your expected power usage. You can do this manually or you can use an online load calculator.
If you want to do this manually, simply calculate watt hours by using each appliance’s power rating, multiplied by the time (hours) it will be running.
For example, you’re running a 10W light bulb for 5 hours a day, a TV(80W) for 3 hours, a phone charger (10w) for 8 hours, and a fan (125w) for 4 hours. Multiply the watts by the hours and add them all up for a daily estimate.
10W x 5 hr = 50Wh
80W x 3 hr = 240Wh
10W x 8 hr = 80Wh
125w x 4 hr = 500Wh
You will need to consider a 20% energy loss in the system, so multiply this number by 1.2, and that will bring your requirement up to: 870 x 1.2 = 1,044Wh
Now you can spec your components based on your energy requirements. This is where you can save a good amount of money on your kit, by working out what's absolutely necessary and what you can compromise on - learn more in our other article. This is point where you should consider if you may need a backup generator, as it may affect your choice of hybrid vs standalone inverter.
Solar Panels - Converts sunlight into DC (Direct Current) energy.
In an off-grid situation, you want to make sure your panels can supply enough electricity to meet your minimum consumption needs all year round. People tend to use more electricity during winter, when solar systems are less effective (shorter days = fewer sun hours). To make up for this, it’s worth your while to get more efficient panels that will still be able to generate power in less-than-perfect sun conditions. We currently offer 330W+ PERC Mono panels, which is costlier but more efficient than more common PolyCrystalline panels. Learn more about our panels.
On average, there are at 239 total days per year with 4 or more sun hours, so we can get a conservative estimate of our panels output based on an average of 4 effective sun hours a day.
320W x 4hr = 1280Wh
This shows that the output from one of our 330W+ Perc Mono panels would be easily enough to cover our daily consumption of 1,044Wh. It will also be able to fully charge a 12V battery in a day.
Battery — Stores energy so you can use it during the night
Batteries are an essential part of an off-grid solar system, as they provide a constant source of stable and reliable power that allows you to power devices when there’s no sunlight. Deep-cycle lead acid batteries are by far the best type of batteries to use in an off-grid solar system. They are designed for the type of deep discharge demands of off-grid use, and have a life-span of 5–12 years. You will want to avoid car batteries at all costs, as they’re designed for supplying short bursts of current and wouldn’t last long when deeply discharged.
Now when we say deep discharge, we don’t mean completely draining the battery like how you might with your phone - you never want to completely drain your battery to 0%, as it will permanently damage your battery and significantly reduce its life-span. We recommend a 50~60% depth of discharge, which is a warranty condition, so work out your requirement by dividing your Wh requirements by the voltage of the battery (most common by far is 12V) and multiply it by 2 for the required Amp hours (Ah). Read more about depth of discharge here.
Using our example:
1,044 Wh/12V = 87 Ah, 87x2 = 174Ah
Based off this calculation, you would be happily covered with one of our 12v200ah Gel VRLA battery. Please note: most off-grid solar systems are run on a 12 or 24V system, if you’re running one Solar panel you will need a 12V battery.
For more information, read our blog ‘The Best Batteries for Off-Grid Solar'
Charge controller - Protects battery and optimises output from panel
The charge controller is a piece of equipment that goes between your solar panels and batteries. It regulates and controls voltage to prevent your batteries from being damaged through overcharging. A highly effective charge controller will also have a significant impact on the output from your panels, increasing your solar yield.
We’ve always recommended our customers to use the MPPT charge controller. It is designed to accept the high voltage input from solar panels, and then charge the batteries at an appropriate lower voltage, while a smart optimisation algorithm is used to maximise the amount of power going to the battery. For more information, read our blog post "MPPT vs PWM."
To calculate the size of charge controller you’ll need, simple divide the size of your Solar panel by the voltage of your batteries. Using our example:
330W/12V= 27.5Ah, so you will want a 30A model to support your 1 panel and 1 battery. and use our 30a EPEVER Tracer 3210an MPPT model.
Inverter - Converts DC power to AC, so you can run your appliances
Most off-grid solar systems will need an inverter. The inverter converts the lower voltage Direct Current (DC) energy produced by solar panels into higher voltage Alternating current (AC), which is what your household appliances will require. Having a good inverter means that all your equipment and appliances will run seamlessly.
You will need an inverter that matches the voltage of your battery bank, and has enough output to run the appliances needed - you’ll need to look at all your appliances and what you’re likely to be running at the same time. For example, a fridge will always be running, but you’ll also want to watch TV at some point, and charge your phone, so you’ll need to be able to support them all running at concurrently. You’ll also want to consider that a having a larger inverter may mean you’re able to run more things than your batteries can support – though this does mean you can add more panels and batteries down the line, without buying a new inverter.
In our example, we have a 12V battery, and are running a 25W light bulb, a TV(100W), a phone charger (25w), and a fan (125w), which is 275W total, so we will only need a 12v 1500w inverter, and we'll have room to add more devices. We’ve always recommended our customers to use a Pure Sine Wave inverter in all off-grid solar installations, to ensure you have the best quality of AC output, that won’t damage your appliance or affect their use.
Wiring all the components together can be difficult for a first-timer, so we include a complete wiring diagram and detailed for all our kits. This is the basics of how a small system would be wired, but they get more complicated as you increase your output and capacity.
Safety is paramount when dealing with DC voltage. To keep your set-up as safe as possible we recommend using circuit breakers between on all cable runs, which we include with all our kits.
Following our example, these will be placed
- Between the solar panels and charge controller (25A)
- Between the charge controller and batteries (60A)
- Between the batteries and inverter (200A)
If you've got any questions that aren't answered here or in the linked articles, please don't hesitate to get in touch and we can help.