Off-Grid Solar Basics for Going GridFree in NZ - 102

Off-Grid Solar Basics for Going GridFree in NZ - 102

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. 

Series vs Parallel Reading Off-Grid Solar Basics for Going GridFree in NZ - 102 10 minutes Next Epever e-Box WiFi App now available on iOS!

Thinking of going off the grid with solar energy? We’ve created this complete off grid solar basics guide to help you!

Learn the basics first with our Solar 101 article.

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, an off grid 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 usage - 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. Keep in mind, heating and cooking are best done on alternative energy sources such as gas or wood-burning, not solar, has they have very high power usage. 

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. Alternatively, you can compare our example usage on each kit page to your intended usage for an easy estimate. 

For example, you’re running a 10W light bulb for 5 hours a day, a kettle for 15 mins (1800W) a TV(80W) for 3 hours, a phone charger (10w) for 8 hours, a minifridge for 24 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

1800W x 0.25 = 300Wh

80W x 3 hr = 240Wh

10W x 8 hr = 80Wh

125w x 4 hr = 500Wh

The fridge doesn't use the same power all day long, so the easiest way to work this one out is to look at the Energy Star Rating - take the yearly kWh consumption, divide by 365 days, and multiply by 1000 to get to the daily Wh number. Eg 221/365 = 0.605x1000 = 605Wh

TOTAL: 1775WH

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: 1775x 1.2 = 2,130Wh

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 the point where you should consider if you may need a backup generator, as it may affect your choice of hybrid vs standalone inverter. 

If you're used to city power, you may have to make some compromises on what you use! Have a read of this article.

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 380W+ 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. 

380W x 4hr = 1520Wh x 2 = 3040Wh

This shows that the output from two of our 380W+ Perc Mono panels would be easily enough to cover our daily consumption of 2130Wh. It will also be able to fully charge a 2 12V batteries 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 one of the best types 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 3-5 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.

Lithium (LiFePO4) are a new and better battery technology, offering a much longer lifespan and more resilience to damage, though they come with a much larger cost.

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% 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. 2 solar panels will require 2 12V batteries for a 24V battery bank.

Using our example:

2130 Wh/24V = 88 Ah, 88x2 = 177Ah

Based off this calculation, you would be happily covered with two of our 12v200ah Gel VRLA battery. Please note: most off-grid solar systems are run on a 12, 24, or 48V 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'

Off Grid 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 the off grid charge controller you’ll need, simply divide the size of your Solar panel by the voltage of your batteries. Using our example:

380W/24V= 15.8Ah, so you will be covered by 30A model to support your 2 panels and 2 batteries, using 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 24V battery bank, and are running a 25W light bulb, 1800W kettle, a TV(100W), a phone charger (25W), a minifridge (75W), and a fan (125W), which is 2325W total, so to run everything at once you'll need a 3000W inverter. But we don't recommend that, as it has a higher standby power usage, and being able to run all of this at once may lead you to use up your battery power too quickly, so we'd recommend a 2000W inverter. This just means for the few minutes while you boil the kettle, you'll switch off the other appliances except the fridge and lights. 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.

Please have a read of our inverter blog to learn about running different appliances with continuous and surge power demand.

Wiring

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. 

Learn about series/parallel connections in off-grid solar use here.

Safety

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 (15A)
  • Between the charge controller and batteries (32A)
  • Between the batteries and inverter (125A)

If you've got any questions that aren't answered here in our off grid solar basics guide or in the linked articles, please don't hesitate to get in touch and we can help.

All this together creates the Weekend Warrior Kit - a great option for campervans or weekend cabins. 

Email us at: info@gridfree.store or call 09 218 5533. You can also message us on Facebook