The Beginner’s Guide to the Solar Backup Generator

solar-backup-generator

If you hate being left in the dark, why not consider a Solar Backup Generator?

Even if you have rooftop solar panels, you’ll still draw power from your utility after the sun goes down or on cloudy days. That’s fine under normal conditions, but when there is a power outage, you’ll be left without electricity. The only way to prevent a loss of power is by installing a backup generator.

A solar backup generator is simply a battery or set of batteries that your solar panels charge up when it’s sunny. If the grid goes down or even when it’s dark outside, you can draw power from that bank of batteries.

If you want to learn more about solar backup generators and how to avoid being stuck in the dark, read on.

Do You Really Need a Solar Backup Generator?

First, be realistic about your situation. Buying one or two batteries is expensive, but the cost can be outrageous if you want to provide backup electricity for your entire house.

Consider how often you lose power. You can think back over your own experiences during storms and other blackouts, or you can click here to check 15 years’ worth of power outages all over the country to find out how often it happens in your region. We suggest you use the Search feature to look for all cases in your area and pay attention to the frequency of blackouts.

Is all the money and trouble worth it for a few days of extra power every 10 years? Maybe you’ve got life-supporting medical equipment in your house that can’t go down or maybe you live in a cold climate where no heat could be a serious issue.

Options for Backup Generators

Which option you choose depends on your current situation – whether you already have solar installed – as well as your electricity needs.

  1. Install New Solar System. If you don’t have solar panels yet, you can have batteries included with an entirely new solar installation. National installers like SolarCity and Sunrun are now offering battery backup systems in certain areas of the US where it makes financial sense for homeowners – mostly California and Hawaii.
  2. Retrofit Battery Backup on Existing Installation. If you are already using a grid-tied PV system and want it to keep supplying power even during power outages, you’ll need to install batteries an additional inverter for the electricity going to those batteries. You can buy a pre-made solar power generator kit that includes batteries, wiring, and everything else you’ll need (check out these solar backup kits at Wholesale Solar to see a few examples). For DIY enthusiasts, it may be better to make your own solar backup generator at home on a weekend, and it is cheaper, too! You don’t even need to be a professional electrical engineer for that – just get the right tools, follow the instructions, and don’t forget about the safety measures. We’ll even walk you through it! Or you can hire the entire project out and have a solar company design and install a custom backup system for you.
  3. Mobile, Off-Grid System. If you don’t want solar panels on your roof and your power needs during outages aren’t as heavy, you could choose a completely mobile, off-grid solution that will not only provide electricity for a few of your critical appliances during outages but could even accompany you on camping trips, tailgating, or anywhere else without electricity. Unlike the first two options, these small generators don’t run off your roof-top solar panels – you’ll also need one or two small, movable panels as well. You can easily throw these solar generators into the back of the car. These emergency battery generators are fully standalone, so you can simply plug in your electric devices into the generator.

Below is more detail on each of these options.

#1 Install a New Solar + Battery System

As we mentioned above, if you haven’t yet installed your solar installation, be sure to talk to the large national solar companies, as both Sunrun and SolarCity both offer solar installations with battery backup. Because batteries add so much cost to the installation, they are currently only offering batteries in places like Hawaii and California, where high utility costs means installing batteries is much more cost-effective.

Costs aren’t publicly available, but considering the limited release, we can assume it’s pretty expensive.

#2 Retrofit Grid-Tied System

If you’re looking to add a backup generator to your solar installation, you have a few choices.

Hire an Installer

It’s still unclear if the big companies will offer to install battery backup on installations they’ve already completed, but if you purchased your own installation (as opposed to financing through a lease or PPA), you can always hire a solar installer with battery experience to design and install a backup solar generator.

They’ll work with you to calculate how much electricity backup you need, what equipment you need, your estimated costs, and where the batteries will be installed.

In the past few years, the state of New York has grown increasingly aware of the importance solar with batteries will play in the future and they’ve created a guidebook for those interested in this setup. To add batteries to a solar system, you need to install the batteries (duh) as well as an additional inverter for the electricity going to the batteries. This setup is known as AC-coupled installation and, while they are less efficient that other installations, they allow you to enjoy electricity from your solar installation even when the power is out.

Back-Up Kits

If you don’t need a custom set-up but aren’t interested in DIY either, pre-made kits might be just what you are looking for.

They come in all sizes, including 5 kilowatt-hours up to 10 kilowatt-hours. For context, a 5 kilowatt-hour solar generator could run your 9-watt LED bulb for 550 hours. When choosing a kit (or any other backup generator, for that matter), you’ll need to assess your energy use and be realistic about appliances or equipment is critical. Your freezer might be critical, but is your microwave? Probably not.

Take a look at the Wholesale Solar link in the section above to see a few examples of solar generator kits, most of which cost around $5,500.

DIY Backup Generators

If you’re looking to spend as little money as possible, DIY is the name of the game. We will talk more about choosing the right elements for the system a bit later, but for now let’s look at what makes up a backup solar generator:

  • You will need a solar panel (obviously)– How many you’ll need depends on how you plan to use the electricity.
  • Next, you will need a battery with 12+ volts rating. If you go to a physical store, ask the staff about a reliable battery, or read reviews online. Once you’ve found one, make sure you get a suitable storage box to protect the battery from the elements, as well as from pets and children.
  • Finally, you’ll need an inverter that will turn your DC energy into the alternating current used by all our electric gadgets.

How much you spend will depend on the size and quality of the products you purchase, but you’ll certainly be spending less than the kits above, especially if you take the time to shop around and find the best deals.

Take a look at this video to see all the components in action, as well as how they are connected together:

#3 Mobile Solar Backup Generator Kits

If you’re looking for a smaller solar backup generator, take a look at the numerous kits available online. These all-in-one systems include batteries, inverter, wires, and in some cases the solar panel as well.

Unlike the kits above, these are designed to be connected to mobile solar panels and move with you. While on trips, just throw them in your car and you’ve got power anywhere you go. At home during an outage, you can simply plug your electrical gadgets straight into the generator and keep using those critical appliances.

At around $500, these kits are much cheaper than the larger backup kits above, but also hold much less electricity as well.

Here are a few popular models:

  • Among the most highly reviewed solar backup generator models are GoalZero’s Yeti. Depending on your energy needs, they make 150, 400 and 1200Wh portable batteries (as you can see, much smaller than the stationary kits above). You can charge them from your utility at home and take it with you wherever needed. To charge it in the wild, you will have to purchase an additional compatible solar panel. Together, they make a solar backup generator kit.
  • Monerator offers a lighter and affordable alternative. The trade-off is less power – while the latest Yeti model provides 1200Wh, this one gives only 128Wh (or 256Wh, if you get a more advanced version weighing ~3 kg). Still, it can serve you well during a short outage or a family camping trip.
  • BePreparedSolar provides powerful solar backup generators. The kit includes panels of 5000 Watts – enough to charge your devices and then some. The downside is its clunky look and lack of a power usage indicator.  While the former may not matter to all, the latter may be a nuisance – you will probably want to see how much energy is left in the battery during a blackout. Still, it does what solar backup generators are supposed to do – provides you power when and where you can’t access utilities.
  • One last model we’d like to mention is Renogy’s 20W All-in-One Generator Kit. This solar backup generator doesn’t require any purchases of solar panels. Everything you need comes in one ready-to-use stylish package, weighing 12 pounds. The pricing is reasonable and the portability is exceptional, as both the panel and the battery come in a small suitcase-like box.

As you can see, the choice of models is abundant – you are free to choose one that suits your personal requirements!

Choosing the Right Components for your Backup Generator

If you’ve chosen to DIY or even if you hire out the design and installation, it’s always a good idea to understand how the components work together and how to choose the best ones to fit your needs.

Batteries

No matter which option you choose, learning how long different types of batteries last pays off. Let’s talk about the most common options and see which is the most practical! You can also check out this quick and easy review of the top 3:

  1. Lead Acid Batteries: This battery type has been used by the solar energy industry for decades. The majority of solar backup systems use this kind of power storage because they are affordable, sturdy, and reliable. When charging, lead acid batteries produce hydrogen and oxygen and can become hazardous, especially in case of frequent overcharging. If you don’t have the more expensive sealed batteries, it is advisable to keep the battery box well ventilated to keep the gas inside from reaching dangerous levels. Other than that, these batteries are quite practical and easy to use. They will likely serve you for 5-15 years.
  2. Lithium Ion Batteries: These are most commonly used by electronic devices, as they allow for ongoing recharge, have superb energy storage potential, and last longer. However, usage of lithium-ion batteries in large-scale solar systems for private houses is not yet affordable. The prices may vary anywhere between $500 and $950/kWh. Still, innovative companies like SolarCity and Sunrun in California and Hawaii have already begun incorporating them into residential solar installations with the Tesla Powerwall.
  3. Flow Batteries: These, much like lithium ion batteries, are currently too expensive for the mainstream residential market. However, if the price goes down, they could be a real option in the future. They are considered to have the longest lifespan of all energy storage technologies, and you can increase the power of a flow battery by simply adding more electrolyte. With other solutions, the only option is purchasing more batteries.
  4. Nickel Cadmium Batteries: Their key advantage is that they don’t freeze or discharge themselves, as others do, but this pro hardly justifies the cons. Cadmium is considered highly hazardous, so discarding the battery will be difficult.

Right now, the most sensible choice of a battery for your solar backup generator would be a lead acid one – affordable, efficient and relatively long-lasting. Lithium ion is increasingly becoming a legitimate option, as notably Tesla continues to build its Gigafactory. Flow batteries may catch up in the coming years, but so far the options are scarce.

Solar Panels

Much like the battery, your solar backup generator cannot function without PV, or photovoltaic, panels. If you are adding a backup generator to your existing system, you won’t have to worry about solar panels – it’s already been taken care of.

For the rest of us, these solar cells can serve a household for 20-40 years, so taking the time to choose the right ones for your situation is a good decision!

Nowadays PV panels are cheaper than ever. Their cost has reduced by a whopping 70% in the past years, thanks to mass production in this maturing industry, down to just $0.49 per watt in 2015! So, for an average sized 5 kilowatt installation, your total solar panel cost adds up to about $2,500.

If you don’t want to invest a mini-fortune in a full-blown solar PV system just yet, here’s good news for you – building a standalone solar backup generator with a single panel or two can be very cheap!

The cost will also vary depending on the planned usage of your solar backup generator. If you lead an active lifestyle and your main reason to get a PV system is to have energy on the go, you’ll need a rollable or folding panel. These can be more expensive than your ordinary solar panels. To cut down the price, an alternative solution is a rigid panel with a sturdy stand and a carry bag.

Solar panels come in many different qualities; there are economy, standard, and premium options. The former is perfect for building a backup generator on a budget – it may not be as efficient and weather-resistant as the other two, but they get the job done. Standard panels are optimal in terms of their performance, durability, and warranty support (generally the cheaper the model, the shorter its warranty). Most solar panels offered on the US market are in this category. Premium panels, of course, are superior in metrics and specifications. They tend to deliver the highest returns on investment, but come at a price. Premium PV panels are best for homeowners who want to maximize solar energy production despite limited roof space.

Inverters
solar-power-setup

Finally, once you’ve bought the best solar panel and battery for your solar backup generator, it’s time to put them to work! For that, you will need a good DC/AC inverter, which is responsible for transforming the power generated from sunlight into usable electricity. This is its main function, but modern models also take on system performance monitoring and battery management. In a way, it can be considered the brain of any power generator – without it, the other parts can’t function.

Just like batteries and solar panels, inverters come in different types. Some of them, due to size and other specs, are only suitable for full rooftop systems, while others can be bought for a homemade standalone generator.

  • String inverters have been in use for a long time, and they work well when all the solar panels are facing the same direction and tilt. Especially large systems or ones with multiple panels on one roof need several of them to function. The problem with these inverters is that if a single part of the system is underperforming because it’s in the shade, the whole module will operate at the same efficiency level as the weakest piece – not ideal.
  • For those who want to be completely independent of the grid, battery-based inverter/chargers are probably the best option. They can be interactive or standalone. The former pushes excess power back to the grid, while the latter doesn’t. Both do a double job for the system: they keep the battery charged to an optimum level and convert solar energy to electricity.
  • If you want a no-fuss solution, there are integrated options. Inverter power panels include the inverter, grounding, power control components, over-current protection devices and electrical disconnects, all pre-installed and ready to use!

For a look at the different brands of inverters, check out this handy infographic.

Finally, you need to remember a few technicalities when buying an inverter. First, it must have the same nominal voltage as the battery bank you have chosen (48, 24 or 12 VDC). Secondly, its size must match your household’s “peak load” requirements – the sum of all AC loads that may be turned on simultaneously. For example: refrigerator (500 watts) + lighting (100 watts) + microwave (1500 watts) = 2100 watts. This is how much your inverter should be able to handle for it to fit your system.

Now you can confidently choose the best parts for your solar backup generator. You’ve learned about what each component is responsible for, what varieties of them are offered on the market, and which is the best for your purpose.

Hopefully, this article has helped you understand the nuts and bolts of solar backup generators, and maybe even build your own system! Which part did you find the most useful? We’d love to hear from you – don’t hesitate to leave your feedback in the comments, and feel free to share this article if you enjoyed it!

Image Credit under CC License via Flickr: 1, 2

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