Grid Inter-Tied Residential Solar Power Systems
The grid-tied solar energy system is the most popular of all the options. This is what 90 percent of our customers choose. And with all the incentives that Washington state offers, it’s no surprise.
Not only do you save on energy costs by 70 to 80 percent with a grid-tied solar system, you’re able to pay yourself back within 7-8 years by taking advantage of all the federal and state incentives available. The system lasts for 25-40 years and, since there’s no moving parts, it never needs maintenance.
So how does the system work with the utility company?
A grid-tied solar power system is directly connected to the home and parallel to the utility grid. These types of systems allow the homeowners to get power from either from the Solar or from the utility grid simultaneously.
Most of the utility also allow net-metering, which allow system owner to send back the access energy to the Grid and get credit, usually at retail rate. Customer can use this credit when there is not enough solar production such as in Winter and or at night when there is no solar production at all.
Any energy that isn’t used by your household/business gets sent to the grid and is immediately used. Your bi-directional net meter shows how much credit you have available and how much you have consumed from the utility company.
The utility company monitors how much you have shared and gives you a credit for that amount each month. Usually it’s in terms of kWh. For example, you might get your utility bill and see you have access credit of 900kWh. If you happened to use energy from the grid the next month, you could use that credit.
In Washington State access energy credit is available to use all year until March 30. On that date, your account goes to zero. Unfortunately, the credits do not roll over.
So, will you be producing access energy that you’ll lose every spring?
No. We take all your household’s energy usage factors into mind when optimizing your system so that it is designed for efficiency. It should not over-produce large amounts of energy credits that you will not be able to redeem.
If you’re planning to increase your energy usage in the future (like adding a pool, for example) we oversize the system to accommodate that. If you know that you’ll be using less energy in the future, we can undersized the system as well.
How many types of grid-tied system are there?
There are mainly two major type of Grid-tied systems, in terms of choice of Inverter (convert DC power to AC), 1) String inverter 2) Micro-inverter are available.
Most residential system with String inverter, usually will have 1-2 string inverters connected to solar modules in multiple strings (1-4) with 6-14 modules in each string. The advantage of these type system is mainly lower cost of material and labor. The disadvantage would be lower production if there is shading and troubleshooting can be difficult and costly if there is an issue with the system.
The other option would be micro-inverter such Enphase inverter or optimizer such SolarEdge. In these types of system every module will have its own inverter or optimizer that sits underneath each module. The advantage of these type system is mainly to mitigate residual shading, with module level monitoring. These systems have additional component and labor, hence the higher cost of system. These systems are easier to modulate for any future upgrade or even add battery storage.
Grid tied systems are the most economical of residential solar electric system, as well as simple to design and install with least number of components.