While many homeowners like the idea of making their own electricity, there’s a lot more to solar panel installation than just bolting photovoltaic panels onto your roof. In fact, solar panels only account for 25-30 percent of the total cost of going solar. It’s actually a complicated process requiring planning, technical know-how, and expensive electrical equipement to create a whole system that’s compliant with stand electrical code and is safely and reliable.
If you’re considering installing solar panels on your home, let’s look at the five important things you need to know about so you can better understand how residential solar energy systems work.
1) Do I Need an Inverter?
Solar panels generate Direct Current (DC) power. Household power is Alternating Current (AC). An inverter converts the solar panel’s DC power output into AC power, maintaining the AC voltage at 110 volts at a “clean” 60 cycles (Herz) per second.
Inverters are rated in terms of watts and must be correctly matched to the panels’ output voltage (or battery if so used). Inverters lose a small amount of power as heat. This can affect their efficiency (the same holds for the other equipment in the system), eating up a few watts you’d prefer to use on something else.
To protect your investment in your system and appliances, inverters should be equipped with sensors that can shut it off during if there is a fault. They should also generate AC current in a pure sine wave, as this will provide clean power to sensitive home electronics.
Important features like these alone can substantially add to an inverter’s price. The most common residential-sized inverter is 5 kilowatts and can cost $2,000 to $4,000. New inverter technology uses micro-electronics that attach to each solar panel, enabling the output of each to be optimized.
2) Grid Tie-In or Grid with Backup?
Basically, grid-tie-in systems let you take advantage of both your solar panels while keeping a connection to your utility company. The problem? When the utility power goes out, it shuts down your inverter in order to prevent it from feeding electricity onto the power lines, which could endanger utility line workers.
Battery backup systems have the added convenience, cost, and complexity of deep cycle batteries, with an average retail price range running $400 to $600 per battery. Many battery backup grid-tied systems include an inverter with a transfer switch that shuts off contact with the utility lines.
Battery backup systems also require controller/regulators. These regulate the voltage and current coming from your solar panels to your batteries to prevent them from overcharging and being damaged.
3) What’s a Safety Disconnect?
For safety, solar power systems commonly require several power disconnects. One is a 600 volt DC fuse (not a circuit breaker) housed in the combiner box. The voltage can be that high because solar panels are usually wired in series which adds all the panel voltages together by the time it reaches the combiner box.
Two other disconnects are at the battery connection (regulator) and the AC output connection to the electric service panel (aka —the household fuse box).
4) How Much Sun Do I Get?
Where you live and where you place your panels have a direct effect on the amount of energy your solar array can generate. How much sun your region receives – called “insolation” – depends on the angle of the sun relative to your area.For example, the insoliation value of central Pennsylvania is 4.0 to 4.5 kWh per square meter per day, while the Texas Panhandle region gets 5.5 to 6.0 kWh per square meter.
Where you place panels also matters. Is the area shaded by trees, shrubs, or other buildings? What is the optimum facing direction and tilt for your longitude and latitude?
5) How Many Panels Do I Need?
The answer to this depends on your insolation and how much of your electrical usage you want covered by your solar array. First, you’ll need to know your usage in watts. If you are putting your system on your roof, then the size of your roof will determine the kind and number of panels your can mount. NREL provides an online PV Watts calculator to give you an estimate on how much solar (and wind) energy is available in your area.
As a rule, the cost per kilowatt-hour goes down as you increase the size. A 5kW system will wind up costing less than a 3kW system because you might be installing higher wattage panels for the 5 kW, but it’s the same number as a 3kw and so the same amount of labor. Plus, you may wind up buying the same-sized inverter and other controllers.
Also try to increase the energy efficiency of your home and lifestyle. Reducing your usage will let you get more value out of your solar installation.
One Easy Answer: Keep it Simple
Transitioning your home to solar is complex stuff. That’s why you should also carefully consider the company you want to perform the installation. Are they licensed to do electrical work? Are they bonded and insured? Are they up to date on electrical building codes and can wrangle the neccesary permits and inspections. More importantly, are they familiar with the state and federal tax incentives that can help save you a substantial amount of money?
Direct Energy Solar is a full-service solar provider. Our premier customer service supports the customer’s entire solar experience — from the individual Project Lead assigned to each customer project to monitoring installed systems when they’re up and running. Our solar experts personally visit your home to measure and assess your roof before we present a proposal. Each installation is custom designed and put in place by North American Board of Certified Energy Practitioners (NABCEP) certifed technicians.
Direct Energy Solar is committed to the belief that the way to spread solar power is to keep your home’s solar installation simple. We want our customers get the most out of their solar panels — from the most energy they can generate to the most electricity savings and the most beneficial environmental impact.