Faqs – Solar Panels, Wind & Off-Grid Energy Independence


How to Add Solar Battery Backup to an Existing Grid-Tied System

How to Equip a Grid-tied Solar System With Battery Backup

  • AC Coupling: Splice your AC wiring to add a storage-ready inverter and batteries
  • DC Coupling: Splice your DC wiring to add a storage-ready inverter and batteries
  • Inverter Replacement: Replace existing inverter with a storage-ready inverter

We’ve noticed a surge of calls lately from people looking to add battery backup to their existing grid-tie solar system.

Many of these calls come from our home state of California, where PG&E has announced rolling blackouts to limit the impact of wildfires. With the prospect of scheduled blackouts looming, solar owners have been pushing to add battery backup to their systems to keep the lights on during grid outages.

Unfortunately, this process isn’t as easy as simply hooking up a new battery bank. Grid-tie inverters are designed to convert DC (direct current) from solar panels, but they are not designed to integrate with a battery bank. You’ll typically need to add new components to make your inverter work with your batteries.

It’s also not cheap. Batteries are the most expensive part of a solar system. Between an appropriately-sized battery bank and a battery-based inverter like the Outback Radian, you’re looking at something like 10 grand minimum to add batteries to an average-sized grid-tied system. (We wanted to make this really clear upfront, since people who call us often get sticker shock when we tell them the backup power package can cost more than the system itself!)

If you are concerned about recent blackouts and want the most cost-effective solution, your best bet may be a power generator. It’s going to cost less upfront, and it may be easier to pair it with your existing system because there are less restrictions on system sizing. A gas generator is usually large enough to back up most or all of your household, where an inverter and battery bank is usually sized to power only the essential appliances, because large battery systems can get expensive quickly.

Gas generators have their own downsides: they are noisy, less environmentally friendly, require maintenance and a fuel source. But there is no question they are the most cost-effective option upfront.

Batteries have higher upfront cost, but are maintenance-free and much more versatile. The main appeal is storing and managing energy produced by your panels so you can recharge with solar during a long-term power outage. Another benefit of using batteries is that they can turn on and provide power to your home almost instantly, usually under 1 second and without any interruption to your appliances. A gas generator will take a few minutes to start the engine, warm up and begin providing power.

If you do decide that battery backup is the way to go for you, this article covers the 3 approaches you can take to get it done:

  1. AC Coupling
  2. DC Coupling
  3. Replace grid-tie inverter with hybrid inverter (storage-ready inverter)

Scenario #1: AC Coupling

Grid-tied inverters need the power grid to operate—they constantly sense grid voltage and frequency and will shut off if it falls out of range.

In an AC coupled system, the grid-tied inverter is paired to an off-grid inverter and battery bank. The off-grid inverter provides a second power source, which effectively tricks the grid-tied inverter into staying online. This allows you to charge your batteries and run essential appliances during a power outage.

The best option for AC coupling is the Outback Radian. The newest firmware supports frequency shift AC coupling, which will work with any inverter certified to EC or UL 1741 standards.

This feature causes the off-grid inverter to shift its frequency to control the output of the grid-tied inverter. The Radian limits the power coming in from the solar array when needed to prevent overcharging the batteries.

Here are the basic sizing guidelines for picking an inverter:

  • The Radian should have at least 25% higher nameplate capacity than the grid-tied inverter.
  • The GS8048A can AC couple with grid-tied inverters rated up to 6 kW (5 kW max for Fronius inverters)
  • The GS4048A can AC couple with grid-tied inverters rated up to 3 kW (2.5kW max for Fronius inverters)
  • Requires MATE3s remote with updated firmware for both the inverter and remote

See the Outback site for more info on using AC coupling to add battery backup to an existing grid-tied system.

Pros of AC Coupling

This is the easiest way to retrofit your system, especially a microinverter system. The battery bank connects to the Radian, which is installed between the grid-tied inverter and your load panels. The existing grid-tied inverter does not need to be removed.

Cons of AC Coupling

Strict guidelines for inverter and battery size make the process of sizing the addition a challenge. The system will perform poorly or not work at all if the inverter or battery bank are undersized. In addition, if the existing grid-tied inverter is large, an AC coupled system can get very expensive.

Compatible With:

  • Most grid-tied inverters on the market

Scenario #2: DC Coupling

In a DC-coupled system, the solar array is connected directly to the battery bank using a charge controller.

This is how off-grid systems work, and it could be done to a grid-tied system if they are using a 600-volt string inverter. This works with the SMA Sunny Boys, many Fronius inverters, or any other 600-volt string inverter.

This Morningstar 600-volt charge controller is designed to retrofit grid-tied systems with batteries. It can be combined with any one of our pre-wired power centers that doesn’t have a charge controller.

The 600V charge controller would be installed between the existing PV array and your grid-tied inverter. It includes a manual switch to switch between grid-tie and off-grid modes. The downside of this method is it can’t be programmed—the switch has to be physically turned to start charging the batteries.

The battery-based inverter can still automatically turn on and power your critical appliances, but the PV array won’t charge the batteries until the switch is turned. So, you have to remember and be on site to turn on the solar charging. Otherwise, you might find your batteries are drained and you won’t be able to recharge from solar.

Pros of DC Coupling

In comparison to AC coupling, DC coupling works with a broader range of off-grid inverters and battery bank sizes.

Cons of DC Coupling

The manual transfer switch means you have to be available to initiate the PV charging. If you forget or aren’t there, your system will still provide backup power, but the battery bank won’t recharge from solar until someone manually flips the switch on the controller.

Compatible With:

  • Most residential string inverters rated for 600 Volt max input

Scenario #3: Replace Your Grid-Tie Inverter With a Hybrid Inverter

The last option is usually the most expensive: you can remove your existing grid-tie inverter and replace it with a storage-ready inverter instead.

This approach is going to be the most flexible option—it works for all existing grid-tie systems. There are a handful of inverters on the market designed specifically to accommodate energy storage for grid-tie systems:

  • The Fronius GEN24 can replace many SMA, classic Fronius and other 600V-1000V string inverters
  • The StorEdge or the SolarEdge Hybrid can replace standard SolarEdge inverters
  • Microinverters would need to be removed and replaced with any hybrid or storage-ready system

Ideally, you want to replace your existing inverter with one that is about the same size and can use the same array wiring.

In many cases, this solution is preferable to adapting your existing system with AC or DC coupling because these inverters are designed from the ground up with energy storage in mind. They include some cool features, like storing energy and selling it back to the utility during peak time-of-use (TOU) periods to take full advantage of your local net metering policy.

This approach is tough with micro-inverters because it takes more work to rip out the old ones and retrofit every panel with a replacement. The labor is a bit more expensive and time-consuming, so an AC-coupled solution is often a better alternative for microinverter systems.

Pros of Replacing Your Inverter

  • Works for any system
  • Storage-ready inverters come with additional features

Cons of Replacing Your Inverter

  • Most costly option, especially for microinverters

Compatible With:

  • All systems

Wrapping Up

Retrofitting solar systems with new equipment can be tricky because of all the different equipment options and various methods for incorporating energy storage. New equipment can change the electrical characteristics for the entire system, and that could introduce faults if the components are not designed to work with each other properly.

If you need help picking the right products to add battery storage to your existing grid-tied system, drop us a line. We have been designing solar panel systems since 2007 and have more than 3,000 solar battery systems in our reference list. Call us +44 333 772 0506 or +1-786-600-1814 or fill out this form to request a free consultation with a member of our design team. We’re happy to help you work out the details.

How do I use a portable generator to power my house?

There 2 ways to connect a portable gas generator to a home: plugging in each appliance with individual cords or powering a circuit panel using a transfer switch.

Cords vs Power Transfer Systems

During storm season the biggest question we get is: “What’s the difference between extension cords, generator cords, and using a switch?

The answer is quite simple. It all comes down to convenience and safety. Let’s break down both types and how they’re used.

Connecting a Portable Generator To a House

No matter what type of generator you have, always consult the owner’s manual for detailed instructions and safety guidelines prior to operation. Under no circumstances should you plug a generator into a wall socket, known as backfeeding. If you go the transfer switch route, get a professional installation.

Extension and Gen-Cords

  1. Follow the generator pre-start checklist.
  2. Move the generator outside (min. 10ft away from openings).
  3. Connect generator to indoor appliances by one of the following ways:
    1. Run one gen cord from the generator and connect multiple appliances.
    2. Run several extension cords from outside to connect to appliances.
  4. Start the generator.

Transfer Switches

  1. Connect the generator to the transfer switch using a gen cord.
  2. Start the generator outside.
  3. Flip the main breakers in the transfer switch from “Line” to “Generator” power.
  4. One at a time, turn on the circuits you want to power.

How Should I Connect My Generator?

Extension Cords

Obviously, the cheapest way to connect your generator is by using extension cords. Except they don’t allow you to use the full power of a large generator. It’s like paying for something, but only being able to use half of it.

What isn’t so obvious is that extension cords are time-consuming and potentially hazardous to use, especially during a blackout in a heavy storm. In fact, using the wrong gauge, length, or a worn out wire can be outright deadly, posing shock and fire hazards.

If you’re using an inverter, and you only need to power a couple appliances like a refrigerator and some lights, a proper extension cord will do the job.

Generator Cords

If you’re using a mid-sized generator and comfortable plugging in appliances during a storm but still want to use cords, your best bet is to invest in a Gen-Cord.

You simply plug the gen cord into the 20- or 30-amp outlet on your generator. The opposite end splits into several household outlets, where you can start connecting additional extension cords safely indoors.

Power Transfer Systems

The best option in terms of power, safety, and convenience, when connecting a large portable generator, are power transfer systems. They contain everything you need to hook up your generator to your house.

More importantly, power transfer systems energize entire circuits instead of appliances. They can power hard-wired appliances – like air conditioners, furnaces, security systems, and lights.

How do I calculate what size generator I need?

Multiply the running wattage of the device by three. Add the running wattage to the starting wattage for the total wattage the device needs to operate. For example, a small refrigerator uses about 350 watts to run, so it’s starting wattage would be approximately 1050 watts, or three times its running wattage.

Can you run a generator without a transfer switch?

It’s not only less safe to run a generator without a transfer switch, but you‘ll limit the devices that your generator can power.

Is it illegal to use a generator to power your house?

In various countries some city authorities require occupied houses have electricity, but they do not specify how that electricity is supplied. It is legal to use a generator to power your house, but whether it’s a good idea is another matter. If you own a larger home it is advisable to have one as a backup electricity source.

How many watt generator do you need to run a house?

You can run the most critical household equipment with a generator rated at 5 to 7kW (5,000 to 7,500 watts). These include things like a well pump, refrigerator and freezer, and lighting circuits. A generator with around 7500 running watts can run all these appliances at once. For an RV or Caravan a 3000 – 4000-watt generator would be ideal; I mean sufficient to fulfill your power needs.

What does a typical solar panel system cost to install?

There is not a clear-cut answer to this question without first gathering your electric usage and information from the installation site. The reason being, there are too many variables to consider when installing a solar system, including how much electricity you use and need to produce, the type of installation, shading, distances and more.

Going on the DIY route definitely will save a lot of money. In general terms installing a solar system by a contractor in the EU would cost you something between 600-1500 Euro.

Contact us to get a free solar quote with exact numbers for a system that best fits your needs.

Does my house get enough sunlight?

Most likely. However, if you have a lot of shading on your roof because of trees or other factors like a chimney or an antenna, solar might not be right for you. Minor shading issues can be overcome with solar panel optimizers or installing a solar system with micro inverters. The best way to know is to contact us to schedule a free site assessment, and we can let you know if your home or business is suitable for solar.

What happens if my panels produce more electricity than I use?

If your solar panels produce more electricity than you need, the excess electricity can be stored in a solar battery;  or will be sent back into the grid and you will receive credit through a process called Net Metering or other similar programs. That credit will be used when your system isn’t producing electricity like at nighttime. Many customers just simply dump the excess energy for example installing an immersion  heater to heat up their pool or they home hot water system.

What should I do if snow accumulates on my solar system?

You can clean it, but in general terms nothing. Let the snow naturally melt from your panels.

Do solar panels work on cloudy days?

Yes, your solar system will still produce electricity on a cloudy day. However, the production will be less than a sunny day.

How much space is needed for solar panels?

There are several factors that impact the amount of space needed for your solar system. Some of those factors include, how much electricity the system needs to produce (this impacts the amount of panels needed), the type and size of the panels that are chosen, and the available space.

For rule of thumb, a 10 kW system to cover a 130 Euro ($160) monthly electric bill would use about 60 sq meter (650 sq ft) for a roof mount and 58 sw meter (0.014 acres) for a ground mount. A 50 kW system would offset a 580 Euro ($680) monthly electric bill and would use about 300 Sq meter (3,250 sq. ft) for a roof mount and 280 sq meter (0.069 acres) for a ground mount.

Will the added weight of solar panels affect my roof’s structural integrity?

Most newer buildings are constructed to support the extra weight of solar panels. If there are any questions as to whether your roof can support solar panels, we will have a third-party engineer do a structural analysis to determine if extra support is needed.

Do the panels need to be placed on my roof?

No. Solar panels can be installed using a roof mount, ground mount, facade or carport.

How long do solar panels last?

The solar panels that we use currently come with a 25 to 30 year linear performance warranty. However, just because the panels are no longer under warranty does not mean they will stop working. Solar panels slowly degrade over time. Most panels are guaranteed to produce 85% of the year one output in year 25. If the panels keep degrading at this rate over the next 25 years they will be producing 70% of their initial output in 50 years. All that to say, solar panels will last a long time.

How much can I expect to save with solar?

Your savings will depend on the size of your system and how much electricity you’re using. 0Bills typically design and build your solar system to cover 100% of your monthly electric bill; but at least to significantly reduce your electric bills.

Will my solar panel system require maintenance?

There are no moving parts in a solar system, so maintenance is typically very minimal. However, if an issue does arise, it is likely covered under  the manufacturer’s warranty. Time to time you solar panels must be cleaned to ensure the constant efficiency of the solar modules.

How quickly can you install a solar project?

Many residential systems are installed in 1-2 days. As a rule of thumb, most commercial and agricultural systems can be installed in 1-2 weeks. However, before the installation can start, in some countries there is usually a 2- to 4-month period when paperwork and permits are completed. Don’t worry, all of this will be completed by your contractor or installer.

Can I self-install an off-grid solar power system?

Of course you can! .. and by the way, you should.  Off-grid solar power is for independent-minded people who want no restrictions on where they choose to live. Off-grid solar power allows you to buy undeveloped land that you can afford more easily. Where other people wouldn’t have power, you will have clean, effective solar energy. Combining your solar pv system with a battery storage, off-grid heating/cooling and DC appliances you can achieve full energy independence easily.

Can I self-install a grid-tied solar pv system?

Many of our grid-tied customers do. Grid-tied solar—for homes that are already plugged into utility power—is less complex to install than off-grid and can be easily expanded.

Because you are tying into the utility grid, your installation may be more regulated. Check out the UK Building Code and regulations, legislation, and policies in your state (USA), and plan to have an electrician or licensed contractor or electrician do the final hook-up to the grid (your main board).

Can I install my own solar pv system?

Yes, of course you can. Over half of our customers install and maintain their own solar power systems. Some of them hire extra help for part of the installation. Most have an electrician connect the wires to your home electrical panel.

If you commit to the research, there’s nothing stopping you from completing the entire installation yourself. Of course, if you get stuck, our experienced support team is here to lend advice and get you back on track. In case you opt for a certified installer just contact us.

What Is the Installation Cost for Solar Panels?

How Much do Solar Panels Cost?

Solar panel cost varies depending on size and type of the system. Solar tiles are generally more expensive than the traditional panels. The prices, though, have been falling in recent years, due to the technological advances.

In the table below you can see the average prices of solar PV systems and the estimated cost and return. As noted before, this is just an estimate since solar panels cost will differ according to quality, type, and size.

Roof Space (square meter) System Size (kW) Estimated Cost (£) First Year Return (£) Profit After 20 Years (£)
8 m2 1 kW 1,500-3,000£ 185£ 640£
14 m2 2 kW 3,000-4,000£ 369£ 3,800£
21 m2 3 kW 4,000-6,000£ 534£ 5,630£
28 m2 4 kW 6,000-8,000£ 700£ 6,750£

The average household needs a solar panel to provide around 3kW. Solar panel cost will range from between £4000 and  £6000 and will cover around 21 square meters of your roof. The more electricity your system can generate, the higher the initial installation cost, but the savings will also be higher in the long term.


It is safe to say that solar panels cost isn’t cheap. Nevertheless, after you have covered the solar panel installation cost, you start saving and making money. Continue reading to find out on how to regenerate your investment from solar panels cost.

What Types of Solar Batteries are Available?

There are six basic types of batteries you can choose from, depending on the amount of energy you generate.

  • RV/Marine/Golf Cart: these batteries are only suitable for small systems, such as boats and campers. They have a short life cycle, since they are not designed to sustain many continuous cycles, but they are the best option for a small system and a limited budget.
  • Flooded: these industrial type batteries are designed to last longer and are reasonably priced. Since they release gas while charging, they must be placed outside or in a ventilated room.
  • Gel: unlike flooded batteries, these type does not release gas and can, therefore, be placed inside. That also translates into better performance, since the batteries maintain a constant temperature.
  • Absorbed Glass Mat (AGM): they are probably the best batteries on the market since they do not release gas, are leak-proof and perform better. They last longer and have a higher quality compared to gel batteries. Of course, they are also more expensive. Since they are the most secure batteries, they are even used for aeroplanes and hospitals.
  • Li-Ion: The majority of new home energy storage technologies, such as the , use some form of lithium ion chemical composition. Lithium ion batteries are lighter and more compact than lead acid batteries. They also have a higher DoD and longer lifespan when compared to lead acid batteries.  However, lithium ion batteries are more expensive than their lead acid counterparts.
  • Saltwater: A newcomer in the home energy storage industry is the saltwater battery. Unlike other home energy storage options, saltwater batteries don’t contain heavy metals, relying instead on saltwater electrolytes. While batteries that use heavy metals, including lead acid and lithium ion batteries, need to be disposed of with special processes, a saltwater battery can be easily recycled. However, as a new technology, saltwater batteries are relatively untested, and the one company that makes solar batteries for home use (Aquion) filed for bankruptcy in 2017.

Different types of batteries can influence how much a solar battery storage system costs. Choose the one that fits best with your budget, energy needs and the size of heating areas to maximise your investment.

How Do Solar Batteries Work?

When the sun is shining, solar powers will produce electricity that you can use to power your home. The excess energy is fed to the batteries. As soon as they are fully charged, the excess power is sold to the grid. During dark hours, the batteries will provide you with the free, clean power stored before, and if it runs out you will automatically be reconnected to the grid. That may happen during the winter, but good storage systems usually store 100% of the energy you need during the summer, and 70% in the winter. You can find solar batteries suitable for any power need: from solar powered boats and campers to hospitals, you can choose systems of many different sizes. It is important to keep in mind that batteries need special care. They should be kept at a constant temperature, with low humidity, which is why indoors types are the best performing option. Moreover, the batteries usually work best when they are fully charged, so you should not discharge them too much (that is, below 20%), to preserve battery life.

What Are Solar Batteries?

Solar batteries are storage tanks that store the solar power generated during the day so that you can use it when the sun goes down. This translates into almost total independence from the grid (usual batteries can cover 70-100% of your energy needs) and even higher savings on energy bills. Moreover, you won’t have to worry about power cuts and expensive or inaccessible power in remote areas. The batteries work as emergency energy storage systems, which can be particularly helpful for companies who are strongly affected by power cuts but can be a huge help to anyone. Just think about how your food spoils in the fridge due to long power cuts. The batteries can be used as an emergency backup for days since they are recharged continuously by the sunlight.

What Is the Lifespan of a Solar Battery?

The average lifespan of a solar battery storage system is around 5 to 7.5 years for lead-acid and 11-20 years for lithium-ion batteries. However, all batteries are vulnerable if they are over-discharged or exposed to extreme weather conditions.

How Do Solar Panels Work?

Solar cells or photovoltaic cells (PV) (comes from the Greek; photo meaning “light” and voltaic meaning “electricity”), convert sunlight directly into electricity. A solar panel is a group of cells connected electrically and grouped into a frame. Many solar panels put together will form a solar array.

PV cells are made of special materials called semiconductors (usually silicon). When light hits the solar cell, part of the energy absorbed and electrons from the atoms in the semiconductor material are released. When electrical conductors are attached to the positive and negative sides, thus forming an electrical circuit, the electrons can be captured in the form or electric current (electricity). This current, together with the cell’s voltage (which is a result of its built-in electric field or fields), defines the power (or wattage) that the solar cell can produce.

How Does Solar Energy Work?

Solar energy is energy provided by the Sun. When converted into solar power, it can be used for heating or electricity by private households as well as businesses. Solar power is generated by a) a surface that collects solar energy and b) a method of converting the captured energy into electricity or heat. There are two main methods of converting solar energy into solar power:

  1. Direct or photovoltaic (PV) conversion. In this case, you would use solar panels (or solar PV) for generating electricity.
  2. Indirect or solar thermal conversion. In this case, you would use a solar thermal collector to generate heat. This is also known as solar water heating.

Can Solar Power Be Stored?

The sun produces insane amounts of energy, generating more power in one hour than the Earth would need in an entire year. Many scientists think solar power is the solution to our dependency on fossil fuel. This view is shared by ZEROhomebills.com as well. Even though many companies and homeowners are installing solar panels on their roofs, the trend is relatively slow but with an increasing trend year after year. That is because solar panels are still not economically accessible to everyone, and using solar power may not seem like the best choice for everyone.

Would you like to know if going solar is for you, take a minute to send us an inquiry. We will do our best to design you a solar package that fits best your requirement. This service is free and without obligation.

For instance, people who only use electricity in the morning and evening may find it inconvenient to install a solar system that only works during the day. In that case, they would still be producing electricity and selling it back to the grid, but the power they would actually be using is still the old, “diamond-priced” one provided by energy companies. Therefore, you would still benefit from a solar panel installation but your home would not fully rely on solar energy. If that concerns you, there is a simple solution available to you: solar batteries.

Does a Solar Panel require Maintenance?

Great news! Solar panels require very little maintenance. You should always make sure they are not blocked with dirt from trees or any other substances that could keep the sun away from them. As panels are generally positioned with some angling, rain will always help to wash the dirt away. Moreover, solar panels should last for around 25 years, but the inverter might need to be changed before; typically between 5 and 10 years.

Can I store the electricity generated by my PV system?

Yes you can. In majority of the cases the electricity generated is either used during the day in the house, or it is automatically exported back to your electricity provider who will pay you for this. In past years battery storage and energy storage products faced a significant drop in price. Both Li-Ion batteries and the conventional lead acid batteries are more an more affordable for households; therefore allows homeowners to store the excess energy for a later use. The battery storage systems available have a lifespan of 10-20 years.

What is the Average Lifespan of a Solar Panel?

Solar panels installed today will produce a reasonable amount of solar energy for about 30 to 40 years, without the need of replacing them. Two our our main suppliers LG and Panasonic are so confident that give 25 years of product guarantee for their solar panels.

How Much Roof Space do I Need for my Solar Panels?

On average, you need 100 square feet (approximately 9.5 sqm) of space to generate 1 kW of solar energy. Considering that a typical household uses around 40-50 kilowatts of electricity per day, it is safe to assume that to supply all of your electricity or heating needs with solar energy, you may need up to 500 square feet (approximately 46 sqm) of roof space. However, already harnessing 20 kW a day from solar energy systems cuts the energy bill in half.

Do Solar Panels Work in Bad Weather?

Solar PV panels can collect solar energy all throughout the year, whether it is spring, summer, autumn or even winter. However, the conversion of solar energy from solar panels is reduced when there is no direct sun exposure. This means that during cloudy days, solar panels work at 50% of their total capacity and on extremely cloudy days, this number may drop to 10%.

Are solar panels very expensive?

While the use of solar energy has been growing exponentially in the last twenty years, the prices of PV cells have been dropping. Currently, the price of each PV cell is 99% lower than it was in 1976. Moreover, because solar energy is such an environmentally friendly solution, many governments are offering grants and incentives for the installation of panels. Based on current average electricity costs, and assuming modest inflation of energy prices, the payback period should be between 8 and 10 years.