FAQs

Enphase Microinverters versus Solar Edge Power Optimizers?

This is a tricky decision. Experts are split on what is better:

Advantages of the Solar Edge System with Optimizers:

-          Microinverters (and inverters in general) have a much higher potential for failure during the expected 30 year system life than do solar panels. With a central inverter it is much easier to replace just the one central inverter when it fails (maybe after 15 years) than to replace a bunch of Microinverters that are sitting under the hot panels on the roof and probably will fail at different times, each time requiring someone to climb on the roof, remove the panel(s) and replace the Microinverter(s). Solar Edge Optimizers try to do the best of both worlds, negating shading losses from individual panels and thus optimizing the system performance, but keeping the heavy lifting of converting DC power to AC to the one central inverter. They contain less electronics and generate less heat, and therefore should be more reliable then Microinverters (we will know for sure over the next 30 years).

-          Solar Edge comes standard with panel level monitoring, on the Enphase this is a $250 upcharge.

• Solar Edge has an inverter system called Storedge designed for integration of a battery back-up system (such as the Tesla Powerwall). People considering integrating a battery at a later time can get the specific inverter designed for this (Solar Edge 7600A-USS), and later add the components needed to add a battery. This solution avoids needing a second inverter to control the battery and probably provides some small conversion efficiency advantage compared to adding a battery backup system to the Enphase Microinverter system.

The advantages of the Enphase Microinverters are as follows:

-          You do not have a big central inverter that you have to find space for to mount it

-          You have 240V AC coming from each panel, which is considered safer than ~500V DC coming down from the roof to the inverter

-          It is easier to add more panels to the Microinverter system. With a central inverter you are limited by how many panels are on each string, and how many strings and maximum power the inverter can take.

Both systems provide:

-          Optimized system performance in shaded conditions over an old fashioned string inverter

-          Rapid shutdown functionality as required by the new NEC electrical code (i.e. the system at the panel will be powerless within 10 seconds when the disconnect switch is activated to protect firefighters).

-          Similar efficiency if you add the optimizer and inverter efficiencies together.

Update as of 7/2022: Read this for a more up-to-date comparison between central inverters and microinverters

10. When do I need to make a decision?
To get the valuable SMART MLP rebate, it's important to move forward as soon in 2019 as possible because there is a limited about of money set aside by the state for Belmont residents. Due to the expected high demand, you should sign up for a free, no obligation site assessment as soon as possible. This will help to determine if your site is feasible for a solar electric system and what the expected cost would be.

11. I have some shade. Can I still participate?
Yes. Even if the shading on your house reduces your system's output below 80% of ideal, you may still choose to participate. Your solar consultant will talk you through the pros and cons of doing so.

12. How can I evaluate if solar is an option for my home?

• Google Project Sunroof provides a quick evaluation of your roofs suitability for solar, how big a system you can install and what your approximate costs and payment options are (Note: this is only available for a part of Belmont so your house might or might not be included)
• PVWatts is a solar calculator developed by NREL, the National Renewable Energy Laboratory, that can provide a good prediction of your house's solar potential and expected costs.

13. What if I rent or own a rental house or a condo?
Renters cannot install solar electric systems, but owners of rental property can. Since each situation is different, you should explain your situation to the installer so they can come up with the best solution. DOER Solar Guide to Condos provides in-depth advice how condo owners can go solar, including how to deal with condo-associations.

14. Can I get more information on SMART MLP?

See Massachusetts Department of Energy Resources (DOER)  draft SMART MLP details.  Final details from DOER are forthcoming.

15. When will I receive the SMART rebate?
Immediately after the installation of your solar array is complete.

16. Does this program offer solar hot water?
Yes, see NeighborhoodSolar.org for details.

17. What is the effect on my property values and taxes?
Imagine two identical homes next to one another, one with solar and one without. It is not hard to imagine that the house with solar would sell for more because it costs less to operate. An article in the New York Times describes a California study that found the premium paid for homes with solar electricity was roughly $5.50/watt, or about $17,000 (which was roughly the installation price of the panels, at the time). A follow-up study from Lawrence Berkeley National Lab described in this article found that among the California homes studied, the resale value increased about $5,900 for each kilowatt that the home’s solar array could generate. You can access the full study here. Although the experience of the California market may not apply exactly to the Belmont market, it does seem likely that the solar panels will add to a home's value. Although solar panels may affect the value of houses, they will not affect property taxes. Under Massachusetts law, solar panels are exempt from local property taxes for 20 years after they are installed.

18. What regular maintenance is required?
Your solar electric panels should be mostly maintenance free over their 25+ year life. You can hose down the panels once or twice a year, but since most panels are tilted, this is not really necessary, as Mother Nature does this for you with rain and snow. Removing snow is not recommended since you risk damaging the panels. It is better to lose a few days of production in the winter (when output is low anyway) than to damage the panels. In any event, snow slides off the panels much easier than the roof because the surface is smooth tempered glass and as soon as part of the panel is exposed to the sun, it starts to heat up and the snow melts off (so be careful what you place beneath your solar panels). Snow guards ($45 per panel that touches the snow guard) are an optional adder which we recommend if this is a concern.

19. Will my solar panels produce electricity during a power outage?
No. The solar electricity is wired separately into your electrical panel, and for safety reasons, is designed to automatically disconnect in the event of a power outage. When grid power is restored, the system will automatically reconnect and synchronize to the grid and your solar electricity will come back on.

20. What is the impact on my carbon footprint?
A 5 kW system should produce about 6,000 kWh of emissions-free electricity per year. This is the equivalent of 3.4 acres of US forest or driving nearly 10,000 miles LESS per year.

21. How about the energy required to manufacture the solar equipment?
According to information published in the magazine Solar Today in June 2012, a solar electric system in Massachusetts generates the amount of energy required to make and maintain it in 0.9 to 2 years. The energy life-cycle analysis was estimated by the Brookhaven National Laboratory.

22. Is solar really viable in New England?
Absolutely! Our available sun power here in New England is about 80% of the sunniest parts of the Southwestern US and is much greater than anywhere in Germany, one of the leading solar countries in the world. (Germany is about as sunny as Alaska!)

23. If we only get 80% of the sun in New England, how can it be viable?
Economic viability is a function of the available sun power and local incentives. Massachusetts is one of the most "solar-friendly" states in terms of economic incentives in the form of SRECs and tax credits. Homes with good solar potential should pay for themselves in 5 to 7 years and generate financial returns in excess of 15%. Homes with less sun have longer payback periods and lower returns but solar can still be a great investment in these situations. In the past, south-facing roofs were generally the rule for solar installations, but nowadays solar panels can be effective on east, south and west-facing roofs.

24. What about the cold?
Colder operating temperatures are actually better for PV! Although it may intuitively seem that the Arizona desert is ideal for PV, the intense heat decreases the efficiency of the modules. Cooler temperatures mean higher efficiency.

25. Will I still generate electricity on a cloudy day?
The electricity production will not be as high as on a sunny day, but your system will still generate electricity because there will still be some irradiance. Under a light overcast day, panels might produce about half as much as under full sun.

26. What happens with my solar array when it snows?
When it snows, the snow may cover the solar panels and affect the production of your system. However, in most cases enough sunlight will still be able to penetrate through to the modules, warming them and melting the layer of snow that is on them. Snow typically clears from your solar panels much sooner than other parts of the roof.

27. Is there a leasing or power purchase agreement option available?
Equipment leasing is an arrangement in which the solar installer owns the panels on your roof and you pay a monthly flat fee to “rent” the panels and receive all of the electricity that the panels generate. Under a power purchase agreement (PPA), the installer again owns the panels and you pay for the electricity generated by the panels each month (which will vary by month). In both of these arrangements, the installer receives all of the tax credits and SMART rebate. Leases and PPAs may be good options for people who cannot take advantage of the tax benefits (e.g., are retired and do not have a large tax bill).

Experts who have studied this issue have concluded that if a homeowner can take advantage of the tax credits and rebates, it is more financially advantageous for him/her to own the system.

28. What is the status of Belmont Light’s policy on emission-free renewable energy facilities?
Belmont Light recently updated its tariff and policy on emission-free renewable energy facilities. The current tariff is effective on December 1, 2015 and is available here. Belmont Light’s tariff differs from full retail net metering offered by investor-owned utilities such as National Grid and Eversource.
Under Belmont Light’s policy, solar energy generated and immediately used onsite by host customer will not result in any charges to the customer. Any solar energy generated by host customers and fed back into the system of Belmont Light will be credited to the host customer’s account at a rate that currently is $0.11 per kWh. After December 31, 2017, this rate may be adjusted, as described in Section 1.06 of Belmont Light’s current policy.  Host customers will pay for all electricity delivered by Belmont Light to the host customer, at a rate reflecting the host customer’s applicable tariff.

29. What if my roof is not suitable to for solar PV? Can I still participate?
Yes, yeloha.com, a solar sharing service, is available. Also, members of BGS are exploring community solar. Your roof may also be suitable for solar hot water.

30. What else can I do to reduce my carbon footprint?
There are four easy things you can do right away. (1) take advantage of a Belmont Light grant to weatherize your home, and (2) go to the Mothers Out Front website and sign up for clean energy. (3) Also, consider an electric vehicle.  See BelmontDrivesElectric.org (4) contact Belmont Light about their heat pump options.

31. Links to additional resources
Massachusetts Clean Energy Center has a number of valuable informational resources for solar on their website. They also administer the PTS (Production Tracking System) for recording solar production used to mint SRECs, the new MassSolarLoan program financed by DOER, manage community Solarize campaigns and many other state programs that support renewable energy in MA.

• MassCEC Solar Information Website
• Establishing the Value of a Solar Home
• Residential Guide To Solar Electricity