Once you’ve had a sip of the solar Koolaid, it can be tempting to just run out into the world, screaming loudly and waving your credit card around. However, making your home grid-independent is a big decision. It’s a big financial commitment and can take many years to give you a return on investment. It also means having to educate yourself much more than the average large purchase demands.
Solar energy is also developing at a rapid pace, which means the there’s always a strong pressure to hold off until the next big thing comes out. This article is meant to help you become aware of the most important factors.
Buy Now or Wait?
Think about the infrastructure that’s in and around the typical home. We are all still using electrical infrastructure that’s decades old. Because infrastructure is so entrenched, it takes a long time for it to change.
Deciding if the best option is to go solar now or later can be hard, because the technology is under strong active development. However, commercial panel efficiency has recently taken a major leap into the above 20% realm. The problem of increasing solar panel efficiency is not an easy one. If you buy a solar power system now it will probably last up to 20 years, by which time a worthwhile improvement will probably be on the table.
Standalone or Grid?
One of the first and most important decisions you’ll have to make before committing to a solar installation for your home is whether you want to be cut off from the grid completely.
For people who live in parts of the world where there isn’t always enough sunlight to power everything you need, falling back on the grid might be the only option available. Alternatively, you could use a fallback generator that kicks in to help smooth out the power flow, but that’s much more polluting, expensive, and inefficient than grid power.
On the other hand, if you get so much sunlight that there’s more power than you can use or store, you can actually sell your excess electricity back to the utility. This is not a way to make money, but it does offset the cost of having to rely on the grid from time to time. In other words, if you sell your unused solar energy to the grid during sunny times, it helps maintain cost neutrality during (literal) dark times.
If you decide to stay connected to the grid, it also means you don’t have to use battery power backup. You can use the grid to act as a backup when there’s not enough power coming from the sun. A hybrid grid solution can also be cheaper, given that battery storage is one of the larger costs.
I have written a more detailed article on solar panel types elsewhere on the site, so I do recommend you go read that for a more complete picture of solar panel types. If you don’t have time for that, this is the basic recap.
There are three types of solar panel cell that are relevant to us as consumers at the moment. These are monocrystalline, polycrystalline, and thin-film photovoltaic cells.
Monocrystalline cells are the most efficient and have the longest lifespan, but they are the most expensive. Polycrystalline panels are slightly worse on every metric, but are substantially less expensive. Thin-film cells are the cheapest yet, but they also have the worst efficiency and lifespan.
The bottom line is that if you go for cheaper, less efficient panels, you’ll end up needing more panels to get the same amount of power. Panel cost and area need to be balanced along with how much space you have and where you can get the best sunlight. At the moment, most people are likely to go for polycrystalline panels for home use, which makes sense. Thin-film PVs are getting better all the time though, so watch out for them in the future.
For example, thin-film PV technology is being used to coat building windows – generating power and keeping the inside of the building cool. Who knows how the technology will be implemented in the future? Because thin-film PV technology can be sprayed onto a variety of surfaces, it could make up for relative inefficiency by just covering every possible surface.
Sizing Up Your Requirements
It’s one thing to say you want to add solar power to your home, but how much solar power should you add? That depends on a number of factors, but you can start by calculating how much power you actually use at the moment. I have a more detailed article on various ways to approach this problem in this article, but let’s start with the main points.
The simplest way is to add up all the power that every appliance in your home uses per hour. Then you need to determine how many hours per day you use that appliance. Add all that wattage together and you’ll know what capacity of storage you need. Then you need to attach enough solar capacity to put that much wattage into the solar storage solution every 24 hours.
This is just a rough description of the calculations that have to happen before you bite the bullet. In the main article you can find the detailed process. You’ll also see that you need some additional margin in order to make up for efficiency losses and, of course, days when you’ll need a little more juice.
Price Per Watt
Different people have different reasons for going solar and/or grid-independent. For many it’s about being free of government infrastructure. Others care mainly about being eco-friendly. Then there’s the financial angle, where solar power will save you money.
Depending on where in the world you live and where your grid power comes from, it may not actually be cheaper to go solar. Even if it is cheaper, it will take many years to recoup the cost of your solar installation. Not to mention the fact that you’ll have to replace the various components again and again as they reach the end of their lifespans.
Regardless of why you actually want solar power, you need to give some thought to how much you are paying per watt. It’s not hard to Google the latest cost figures. Every year the price goes down, so have a look at what solar energy costs per watt to generate and compare that figure to how much you are paying for grid-based power. As I pointed out, solar is not a purely financial choice. However, in your particular case it might be worth waiting a few years until the cost per watt comes down to where you are comfortable with it.
Remember to factor in any money you get from selling your electricity to the grid and also any tax incentives you may get, which we’ll talk about next.
Just as with electric cars, many governments in the world want to incentivise its citizens to go green. The main way they do this is by offering tax incentives. You get to take some percentage of the money that you have spent on going solar from your taxes. Alternatively, the people who sell solar equipment may get a subsidy on solar products with every sale. However it is done, the end effect is that you get to pay less money to go solar. That has an effect on what you end up paying for each watt generated.
Be sure to get the details on any government incentives before you actually buy anything, since it might only apply to particular products or require that you do some paperwork upfront. If you do things right you could save a fortune.
A solar power installation in your home consists of various components. The main ones are the solar panels, the batteries, and the inverter that turns DC power into AC power. Each one of these components comes with an efficiency rating. That is, how much of the energy that comes into that component makes it out again as usable energy. If something is 90 percent efficient and you put 100 watts into it, you’ll get 90 watts out and 10 watts of waste heat, at least in theory.
The best commercial solar panels have an efficiency of up to 24%; that’s under ideal test conditions. Different battery technologies have their own efficiency ratings and you can read all about them in my article on solar energy storage. Finally, a good inverter will have an efficiency in excess of 90%.
In general, the better and more efficient power sources will cost more money, but are worth it in the long run. Sometimes the extra efficiency does not make financial sense over any period of time, but your specific installation needs that level of efficiency to work properly. For example, if your roof space was very limited, then paying more for monocrystalline solar panels makes sense, because you need as much wattage per square meter as possible. Likewise, more efficient batteries might be worth the cost if you don’t have the space for a cheap but inefficient solution. Only your specific situation will determine what’s right in your case.
In case you haven’t noticed yet, the sun moves in the sky over the course of the day. Well, actually it’s US that move relative to the sun, but from our point of view it rises in the East and sets in the West.
Solar panels only produce their maximum power if the sun strikes the panel at the right angle. If your panels are in a fixed position, then they will only work at their peak for a small sliver of every day. That’s actually fine for people living on parts of the world with very strong sunlight. If you live in a location where this isn’t the case, then you might want to consider using a solar tracker.
Solar trackers are add-ons for solar panels that make sure the panel is always facing the sun at an optimal angle, the same way a sunflower turns to face the sun over the course of the day.
Solar trackers come in active and passive varieties. Active trackers use sensors, motors, and other electromechanical components to move the panel so that it’s facing the right way. This is a fast and efficient way to track the sun, but increases cost, complexity, and the chances that something will break. The more moving parts you put into something, the more likely it is to fail.
Passive trackers don’t have any of these failure-prone parts. Instead they use heat, fluid dynamics, and gravity. Liquid is moved from one side of a panel to the other by the sun’s heat. It works pretty well, but it’s not as fast or as accurate as active tracking. Very cold weather can also affect the performance of passive trackers.
Roof or Ground Mounted?
When you install a wind turbine, you have to put it really, really high up. Mini residential turbines have to be about 10 meters above ground. When it comes to solar panels, you’re trying to catch light – something that moves at the speed of, well, light. So having an extra few meters in elevation doesn’t make any difference to your power.
Still, most of the installations we see are on people’s roofs. This makes sense for a number of reasons, the main one being that this is the only place anyone has space for them. However, roof-mounted panels come with their own problems; not least of which is how hard and dangerous it is to access them for maintenance or repairs.
Ground-mounted solar panels are actually a more generally attractive idea if you ask me. They can cost a little more, because you have to build some foundations, put in longer wiring, and so forth. However, in the long run you can actually save money and a lot of hassle.
Not every roof is at the right angle or location, relative to the sun. You can also only put as much solar paneling in place as the existing roof allows. With a ground-mounted system, given that you have the space for it, you can overcome these issues. You can learn more in the main article on the subject.
Inverters are central to solar power in the home. They convert the DC current that solar panels create and turn it into AC current. The classic way is to use a central inverter, but in the last few years solar panels have been fitted with micro inverters. Each panel has its own small inverter. This allows fine tuning of performance and even increases lifespan. Any new home solar panel installation should have micro inverters on the list of options.
If you need power off the grid or when the power goes out, then you’ll need somewhere to put that energy for when you need it. That means getting a battery backup system. These days there are all sorts of choices to make. This is probably the most complex aspect of solar power in the home, which is why I have a longer dedicated article on the subject.
The nutshell version here is that the most popular choice is deep-cycle lead acid batteries. You can get a few varieties of these, but for most people “AGM” lead acid batteries are the best all-round choice. Lithium batteries like the Tesla Powerwall are, however, on the rise, despite still being very expensive. Weirder technologies like flow batteries are also becoming a viable alternative. These use the flow of a special liquid and have the amazing ability to be completely discharged without any damage.
I really recommend you read my main article on solar storage, because there is a lot of info to go through and you will kick yourself unless you consider all the options.
Warranty, Insurance, and Lifespan
When you make a major purchase like this, you don’t want to lose your money. So first of all you want to make sure that you get components with good warranties. That means a warranty that matches the expected useful lifetime of the component in question. Thanks to modern manufacturing standards and materials, you can get more life out of your equipment than the manufacturer is willing to cover. Solar panels can last a long time and the latest units with micro inverters can last up to 25 years.
Be sure to read the terms of the warranty carefully and consider taking out insurance to cover your solar panels being damaged by hail, accident, or theft. It can be an expensive thing to replace out of pocket!
While it would be nice if solar power installations in your home were a fire and forget solution, the truth is that maintenance has to be done over the lifespan of the system. Different components need different types and frequencies of maintenance.
The solar panels themselves can get gunked up by dust and other substances settling on the surface. So giving them a clean when their output starts dropping is one obvious form of maintenance. If you are using a solar tracking system then the mechanical components may need to be oiled and checked at regular intervals, in line with manufacturer recommendations. Inverters may need to be checked from time to time in order to make sure none of the capacitors are swollen or otherwise damaged. Depending on what type of battery backup technology you choose, you may also have to inspect your batteries regularly and make sure they are still working properly.
The cost of this will depend on who does the maintenance and inspection work. If you learn to do much of it yourself, you’ll save a bundle of money over the years. Otherwise, it’s best to pay someone to do it for you. It might even be a condition of your warranty and insurance that inspections and maintenance are done by a qualified professional. Speaking of which. . .
I strongly advise against installing any of this stuff yourself. A lot of the red tape concerning solar installations center on qualified people doing the work. Yes, labor costs can be significant, but it’s better in the long run. Also, if something goes wrong, you can make a claim against the guarantee on labor. You can’t do that if you mess things up yourself!
A professional installer will survey your home and also give you great advice about many of the points I discussed above.
Armed and Ready
These are the most important core issues and facts that you should be armed with before laying down money on any solar panels. I know it is a lot to take in, but the last thing you want to do is be stuck for decades using the wrong, sub-optimal solution. Measure twice, cut once!