Solar: Frequently Asked Questions
Table of Contents
How Does Solar Power Work?
How does a solar system generate electricity?
A solar energy system generates electricity through the use of photovoltaic (PV) technology. PV panels turn the sun's light energy directly into electric energy. The electricity generated by a solar PV system works just like the electricity delivered by the utility. After passing through a component called an inverter, the direct current (DC) electricity generated by the solar panels is converted to alternating current (AC), the type of electricity that you access through the outlets in your home or business.
How much electricity will a solar energy system produce?
The amount of electricity generated by a PV system is dependent upon several factors, primarily system size, orientation of the system to the sun and shading issues from nearby building or trees. Typically, a fixed PV system using 100 square feet of solar panels (this consists of four to five solar panels that will generate about 1,000 watts) will produce about 1,100 kWh per year if well oriented with no seasonal shading issues.
What can affect the amount of solar energy received?
The strength of the solar energy (radiation) available depends on the time of year, the time of day, and the latitude of the generation point. The amount of energy generated can be further affected by the amount of dust and water vapor in the air, the amount of cloud cover and any shading of the solar panels, and the quality of the solar modules.
How does electricity get stored for use after the sun goes down?
Grid connect systems direct excess electricity produced during the day back into the local electricity grid. You then receive a credit for any power that your system supplied to the grid. During the night when your system does not produce electricity, you draw your power from the grid unless you have battery storage.
What happens with grid-tied systems during an outage?
The grid connect inverter will automatically shut itself off within a few milliseconds of an outage, to avoid the potential of a dangerous “brown-out” in your home and to prevent back feeding into the grid. Therefore even though you have a solar system during a blackout, you will not have power available. If you want to keep on having electricity available during a blackout then you would need to have back up batteries installed as well, which will add to the cost of the system.
What is the difference between solar power and solar hot water?
Solar panels take light from the sun and make electricity. Solar hot water systems take heat from the sun and heat water. It is easy to remember: Heat from the sun heats the water. Light from the sun turns on the lights.
Investing in Solar
How much does a solar energy system cost?
The total cost for purchasing and installing a solar energy system is based on the system size you require, and the specific details of the layout of your property. Solar energy systems can range from $3 - $7/watt ($3,000 to $7,000 per kW). However, we encourage customers to obtain three or more bids from qualified contractors before purchasing a system.
What is the likely payback on my investment?
Payback time is determined by many factors, most importantly the amount of your current electricity bill. Customers with lower bill amounts typically have a 20-plus year payback period. Customers who have larger bills may see a shorter payback period. BED's Energy Services staff is available to work with customers to help estimate likely paybacks along with the estimated environmental benefits. How long does the system last? The lifespan of a solar photovoltaic panel is approximately 20-30 years, while the life-time of an inverter is approximately 10 years. Check with your solar installer for warranty information.
Will a solar energy system produce enough energy to handle all my electricity needs?
For the average BED residential customer, a PV system will produce 35- 50% of the customer's annual energy needs. The proper size of the system depends on how large an investment you want to make and how much un-shaded roof or ground space are available. Including energy efficiency improvements with the PV project can help to increase the percentage of annual usage that the PV system covers. BED's Energy Services Staff can assist you with analyzing your energy efficiency opportunities and savings.
Will I still get an electric bill?
Yes. Your grid-tied system will produce most of the electricity you use, but typically not all of it. You will have a lower Burlington Electric bill thanks to your solar array.
How am I credited for my excess generation?
When power is supplied to the main grid, the home owner receives a credit on their bill for that electricity. Visit our Solar Billing page for more details.
Getting Ready for Solar
Do I need to be connected to the grid for net metering?
Yes. To qualify for all net-metering benefits, the system needs to be connected to the utility grid. Customers must install a separate generation meter to record the kilowatt hour (kWh) output from the PV array. This requires having a licensed electrician install a separate meter channel, which the customer will be billed for. Currently, residential meters cost about $150 and commercial meters about $350. What is a grid-tied solar power system? Grid tied systems supply solar electricity through an inverter directly to the household and to the electricity grid if the system is providing more energy than the house needs at any given time.
How much roof space do I need for an installation?
For every kilowatt (1 kW = 1,000 watts) installed, a solar system takes up about 100 square feet.
How old can my roof be?
Your solar professional can provide the best guidance. We recommended that the roof be in good shape and all necessary roof replacement or repairs occur before the panels are installed.
Can I increase the size of my solar energy system at a later date?
Yes, provided you have the available roof or ground space.
How do I know if I have a good site for a solar installation?
Qualified solar professionals can tell you if your site has the proper orientation, good exposure to the sun, and an adequate amount of structural support and space for solar panels to be placed. They can also advise you on ground or pole-mounted options.
Who are qualified professionals?
There are many professionals installing net metered systems throughout Vermont. We recommend customers talk with other system owners and ask for references. For a complete list of professional contractors, customer may also want to visit the Renewable Energy Vermont. Do you recommend installers? BED offers the Solar Shopper Program where we have partnered with Building Energy; Catamount Solar; DC Energy Innovations; Peck Solar – A Division of Peck Electric; and Vermont Solar, LLC in an effort to offer an in-depth comparison shopping tool for a fee. Click here or more information.
Who can help me obtain the necessary state approvals to connect my system to the electric grid?
Most professional net metering system installers will assist you with the application process at the Vermont Public Utility Commission. Please ensure that your installer also contacts both the City Electrical Inspector and BED to review the installation and interconnection to BED's system. Installer information is available here.
Where do I submit my application?
Although your chosen installer will typically start the application process, the form can be found on the Vermont PUC website. If BED has any questions regarding your application, we will reach out directly.
What are the steps for getting my solar project approved?
- (Optional/Recommended) It is very beneficial to share system designs with BED to verify proper metering and interconnection before starting the interconnection process. We find that not having to change your design in the middle of the process can save time and potential costs.
- With your solar design ready to go, obtain any required permits from the City of Burlington. All permitting is completed through the City of Burlington Department of Public Works (DPW).
- In addition to permitting, you need to file a Registration/Application for a Certificate of Public Good (CPG) with the State of Vermont. The Vermont Public Utility Commission offers the video "How to file a Net-Metering Registration, Application, and Petition" on this process to help you in the process. Vermont ePUC Rule 5.100 - Construction and Operation of Net Metering Systems governs the registration/application of net-metering projects.
- BED is notified automatically when a CPG has been filed with the state and we will review the CPG at that time.
- With the appropriate permits in place and the CPG filed, you are ready to install the system. If you haven’t done so already, it is a good time to review the interconnection plans with BED so any required changes can be made before installation.
- After the system is installed, schedule an inspection with the Department of Public Works electrical inspector. In addition, you will need to submit a Service Application to BED. The service application notifies BED that you are requesting the installation of a solar meter and/or net-meter at a specific location. Generation meters are only to be provided and installed by BED. In addition, BED will not energize any system without proper inspection from the City of Burlington electrical inspector and a permission-to-energize notice from the inspector.
What Do I Get Credit For?
Understanding Net Metering
Solar customers are billed using a system called Net Metering. A net-metered system is a renewable energy installation (like solar or wind) that you own and is connected to your building and to the electric grid. If a renewable energy system produces more power at any given moment than the property consumes, the extra power will flow into BED’s electric grid and the customer may receive a credit. A special bi-directional meter or net-meter (provided by BED) measures the amount of electricity used from the grid and any excess electricity sent to the grid.
Net metering is the process of measuring the difference between the electricity supplied to a net-metered customer from the electric grid and the electricity generated by a customer's electric generation system (typically, a photovoltaic array).
The timing of when electric power is consumed and generated is an important factor in determining how much of a bill credit, if any, can be earned in a given month.
In the example below, a customer's property used 1,000 kWh during a month when their system generated 600 kWhs. However, the customer didn't use all 600 kWhs when that power was being generated. This is common if, say, the customer isn't home using their appliances or lights during the middle of the day when most solar power is generated. Because of this, we keep two separate running totals: how much unused solar generation you put back onto the BED grid (the green boxes below) and how much of BED's electricity you needed to power your property (the brown boxes below).
The rate BED charges per kWh for usage may be different from the rate we credit customers for their excess generation sold back to us. This is why we have to keep the two separate totals. Learn more on our Solar Billing page.
Where can I go for more information?
Our Energy Services Team is available to explain the net metering tariff in more detail and answer any questions about net-metering systems in Burlington. Contact us by e-mail or call 802-865-7337.
The Vermont Department of Public Service also provides a Guide to Residential Solar that offers a lot of useful information on solar PV systems.