Preparing for future solar panels
whitenack
| Posted in Green Building Techniques on
Building a new home and want to install solar panels at some point in the future. They won’t be in the budget initially, when the house is built, but I want to prepare for them and make sure I don’t miss something during the construction process that I will have to redo.
The panels will not go on the roof, they will go out in the yard or on an outbuilding or pergola, so I don’t have to worry about running wires from the roof to the basement. However, do I need a particular type of breaker panel? Do I need to spec certain equipment?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
If it's going to be on a roof, among other things the roof has to be verified strong enough to handle the additional weight. It's cheaper to get this part right from the get-go than to bring it up to snuff later.
A couple of decent checklists for solar-ready building:
https://www1.eere.energy.gov/buildings/residential/pdfs/rerh_pv_guide.pdf
http://www.nrel.gov/docs/fy10osti/46078.pdf
Thanks Dana. I'm not ready to build the structure that will hold the panels. I'm just checking to see whether my home infrastructure need to be specific items or if the solar parts are all independent and added later.
Clay,
If you have a mechanical room near your electric meter, leave room on the wall to install disconnect boxes and the inverter. If you know where your future PV array will be located, remember to include a plastic conduit through your foundation for the future buried cable.
Presently the electrical code allows you to backfeed your PV output into your breaker panel at up to 20% of the breaker panel's rating. So if you have 200 amp service you can backfeed 40 amps of PV through the panel, or 9600 watts of PV. If you have an idea of how large of a PV system you will want and if will be larger than 9.6kW, you may want to either have a larger electrical service installed or make other provisions for how the PV energy will enter the electrical system. It would be worth talking to a dealer/installer to get info on what is required locally and what you need to do to be ready. At a bare minimum, follow Martin's advice above.
When we were planning and in the process of our house build, we (like you) wanted to get solar, but weren't sure when it would work out financially. We solicited advice from solar installers and relevant contractors, but it was hard to comprehend even the basic details due to our inexperience. So, it might be helpful to hear from someone who has been in your shoes. Apologies if this is too basic for you.
Solar PV systems can be installed in houses with no foresight, but some planning will definitely make it easier. As others have said, it would be worthwhile talking to your preferred installer and having them talk you through the entire process and what needs to be done to prepare.
If you're going ground or accessory building mounted:
-make sure you have space on your land with unobstructed southern exposure...without lots of trees in the way so you don't have to clear cut your land...as part of giving you a consult or quote, installers will use a solar evaluation device to analyze your solar potential (and any shading issues)
-conduit will need to be run from the installation to your house, make sure you don't have ledge near the surface or other obstacles that will complicate the trenching
If your mechanical area (and breaker panel) is in the basement, you may not have to do much planning because (I'm assuming) the inverter and relevant conduit/wires/etc can just be installed on the basement walls without worrying about wood framing and finish work. Based on our system, the conduit/wire from the panels will run to the inverter and then into your breaker panel.
You should look into your local and state regulations/incentives/rebates/policies that relate to solar. As an example, in order to get a rebate from our utility (in exchange for giving them our RECs), we had to install a separate meter that only recorded solar output, this had to be installed on the exterior so it could be read anytime. Not a big deal, but would have been nice to prep for this small meter enclosure and additional wall penetration (conduit).
If you think there is any chance an off roof mount won't work out ($ issues, site conditions), give some thought to whether panels can be installed on your roof and where the conduit would pass from the panels to the basement.
Thanks for the replies everyone.
Thanks for the response Brian. That sounds like us exactly. We are sure an off-roof solution will work since we are building on farmland with lots of clear area.
Jim, what size electrical service do you recommend? This location has no gas, so everything will be electric and I don't want to run out of room. Would 300 amps be silly overkill? 400 amps?
You would need to estimate your electrical usage and the proportion you hope to offset with your PVs and figure your electrical service requirements from there. We live in an old farmhouse with 100 amp service so my back-fed PV production is limited to 20 amps, and that is adequate for us, but we are real energy tightwads. We do have an electric car and mini-split heat pumps for spring and fall heating but rely on wood heat for the really cold weather.