Newbie here, Off-grid or On-grid for my needs?

NCSolarGarage

New Member
I'm looking to DIY a solar set up for my house/workshop but I'm unsure if I should go fully off-grid, or keep it grid-tied. I've done plenty of reading over the past few years, many youtube videos, etc. I guess the internet knowledge means I'm about an expert now, right? Hah!

Anyway, I'm building the system out of hobby, and the learning experience of DIY. My property is approx 1.5 acres, house is 1600sq ft ranch, I have an in-ground pool, and a 2400sq ft metal building. The house will need to power the heatpump, dryer, water heater, pool filter, among the other usual loads. I also have a tesla I need to charge for approx 50mi/day (I currently only charge on 120v). Without the car, the house averages 13-25kwh a day. The metal building is on a separate meter, and where I plan to roof mount the solar panels. The shop is insulated with a heatpump that I only use when I'm working on projects, which is the main load in there. I also keep my 50A tesla charger in here should I need a 'top up' for a longer drive. I do need to power a lift, and a car chassis dyno, but these are infrequently used.

The shop is about 150ft from the house, PVWatts estimates about 15kw will fit on the shop roof and produce roughly 20k Kwh/yr.

I don't know if I can take the house completely off grid and wire the panels solely to the house? I live alone, and don't mind 'juggling' the loads if need be. Or if I should supplement some of the power to both house and shop while keeping both on-grid, or take the shop off-grid and supplement extra power to the on-grid house, etc? I certainly need to decide this before equipment, so therein lines the issue. Suggestions?

Thanks for the wonderful forum!
 

Rednecktek

Solar Enthusiast
Be aware that in a lot of places there's "Grid Tie" where you are plugging your solar system into the existing grid to DRAW extra power, there's "Grid Tie" where you're JUST feeding power into the PUD (Like the local companies selling 4Kw roof installs to all the neighbors in town), and there's "Grid Tie" where you're actually feeding power back to your PUD AND able to draw from your system if there's an outage (Think Tesla's PowerWall type setup). Most of the latter versions require permission from the PUD and county, inspections, certified installers, permitting, etc to jump through before they'll let you do it.

If you can fit 15Kw of panel and only generate 20KwH per year, that's only 1.3 hours of sun per year. There's something wrong with that math or you live in Scotland. :p

If you want to be able to run completely off grid you're going to need to get some SERIOUS battery banks installed. A good rule of thumb is 3 days of no sun, which in your case would be 75KwH of battery Don't forget to factor in not only the cost of the equipment, but where you're going to physically mount all the things. Those batteries are going to have a significant footprint and you don't want to scratch the car.

Speaking of the car, that's 11Kw right there for your charger, bringing you up to 36+Kw of power. Not unreasonable, you'll be looking at something like the 6KW Split Phase inverters to provide the 220v supply you need anyways for the heat pump, dryer, etc.

So yeah, if you've got the budget then the next step is to track down your county office and the PUD office and figure out what hoops you have to jump through to connect it up to the grid. Pick out your basic hardware (Which SCC, how many panels, what size and length of wire, how many batteries of what kind, etc.) and doodle together a plan. Then come let the folks here look it over for whatever it is you missed, because we ALL have missed something in our first systems before. 😩
 
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