GRID-TIED SOLAR SYSTEM – FREQUENTLY ASKED QUESTIONS
Some questions come up regularly when people are considering installing a grid-tied solar system. So we took the initiative to group them on this page.
10kW grid-tied solar system- Écosolaris project – summer 2017
Can I disconnect from Hydro-Québec ?
Although many people would like to disconnect from Hydro-Québec’s network (especially when rate increases are announced :), it is rather ambitious to think of doing so unless you have an energy-efficient house. The main challenges we face are the uneven periods of sunshine, the power required by some energy-consuming appliances and the space required for the installation of solar panels.
Uneven periods of sunshine
At certain times of the year, especially in winter, the sun may be out for several days. It is therefore necessary to provide for the use of batteries in order to store energy that will be used later, which adds a significant cost to the system.
The power required by some energy-consuming appliances
The heating system, the water heater, the stove, and the dryer, when powered by electricity, require a very high electrical power, which poses a particular challenge for a solar system.
Space required for installation of panels
The number of solar panels needed to produce as much energy as a small house that has not been built to the highest standards of efficiency can be as high as 80. Knowing that a panel is about 3.5 pi x 5, pi (1m x 1.5m), the necessary roof space is very important.
So, what is the best way to proceed ?
The best way to proceed is to remain connected to the Hydro-Québec grid while producing some of its electricity through solar panels. To do so, all you have to do is register in Hydro-Québec’s net metering program.
How a solar system connected to the Hydro-Québec grid works ?
The operating principle is very simple. Solar panels produce direct current that is converted by one or more AC inverters before entering a circuit breaker in the home’s electrical panel.
Will Hydro-Québec buy the electricity generated by my solar panels ?
No. The electricity that your solar panels will produce will be consumed immediately by the appliances in your home and the surplus will be returned to the Hydro-Québec grid, which will credit them for future consumption through its net metering option.
For example, some projects come up with the concept of “net zero” which, on an annual basis, produces as much electricity as it consumes.
Can I produce more than I consume ?
No, the production of your solar system must not exceed the consumption of your home. You must use your surpluses within a maximum of 24 months otherwise they will be lost.
Will I need batteries ?
No. It is not necessary to use batteries in a net metering system. This is the advantage of this kind of system. The use of batteries increases costs significantly.
So, why use batteries ?
In the event of a failure of the Hydro-Québec system, a solar system without a battery storage system stops producing for safety reasons.
The addition of a battery storage system to the solar system, such as the Tesla Powerwall, for example, makes it possible to palliate to a temporary lack of electricity, a bit like a generator.
In the future, the use of batteries will also allow to save money by reducing power consumption from the grid during peak periods during which electricity rates will be higher. Hydro-Québec is currently working on a variable rate program to which consumers can subscribe on a voluntary basis.
What is the power consumption of my house ?
Power consumption is expressed in kWh. You can find the electricity consumption of your home on your Hydro-Québec bill.
In the example below, the power consumption is 25 590kWh on an annual basis
What is the power of the solar system that will fully fill my consumption ?
Simply divide your annual electricity consumption by 1200, which is, on average, the annual output in kWh of a solar system with a power of 1kW, inclined at 45 degrees and facing south in Quebec
In our example:
25 590/1200 = about 21 kW
How many solar panels does that represent ?
Simply divide the power of the system into watts by the power of the panel model that will be used.
Example using 300W panels:
21kW * 1000 = 21,000W / 300W = 70 panels
Conversely, how to determine the annual production of a solar system of a given power?
To do this, simply take the power of the system in kW and multiply it by 1200. This value is true for a solar system located in Quebec, facing south, and whose panels are inclined at 45 degrees.
Example of an annual production of a 5kW system in Quebec:
5kW * 1,200 = 6,000kWh
For a more precise value, it is possible to use a calculator like PVWatts which makes it possible to estimate the annual solar production according to the particular orientation of your house and the angle of your roof.
Here are the steps:
- Enter the city of residence:
- Confirm the weather station used
- Indicate the power of the system, the expected installation angle of the solar panels or the angle of the roof and the price of electricity
The calculator will tell you how much energy the system should produce as well as the estimated annual savings.
What is the lifespan of solar panels ?
Solar panels have a lifespan of more than 25 years. Solar panel manufacturers also guarantee that the power of their panels will be equivalent to 80-85% of their original power at the end of this period.
Should the solar panels be cleared from snow ?
This is a personal choice. Depending on the angle of the panels a greater or lesser amount of snow can accumulate on them. The snow will eventually disappear after a few days depending on the outside temperature and sunshine. Of course, this process will be speeded up if you do the snow removal on your own but the panels need to be easily accessible.
Does a photovoltaic system require maintenance ?
No. No special maintenance is necessary.
What is the difference between a microinverter and central inverter system ?
The solar panels produce low voltage direct current electricity that must be converted into 240V alternating current in phase with the Hydro-Québec grid. There are two approaches to achieving this result.
A small device, fixed behind each solar panel is responsible for converting the current produced by panel to 240V, in phase with the Hydro-Québec network
- High flexibility in positioning panels with multiple orientations
- More efficient than central inverter when some solar panels are shaded
- No appliances to install inside the house
- More expensive for installations with multiple solar panels
A number of solar panels are connected together, in series, to create chains. A single unit installed in the house is responsible for converting the current from the panels to 240V.
- Less expensive for systems with a lot of panels
- Less flexible in positioning panels with multiple orientations
- Less efficient than microiverters when some of the solar panels are shaded
- Space required inside the house