Congratulations on your decision to go solar.
It’s a little more complex than going “as big as you can afford”. Most utilities will give you next to nothing for your excess power. Why spend more money on panels than you need or can afford? Also, do you plan to buy outright or lease? I purchased my system and calculated my ROI to be about six years, plus I’ll get some residual value of my purchased system when I sell the house.
If you lease a system and want to move and sell your house with leased panels, the new buyer will have to agree to assume your lease in most cases. Could be a deal breaker, maybe.
Unless you’re excited about doing all the research yourself, you probably need a consultant or a company that can visit your site and make all the calculations, specifically taking a look at current, annual needs and then factoring in future consumption for your Model 3. I “gas” up my Model S about once a week, so I use about 300 kWh per month. On average, my system generates a little over 1,000 mWh/month. Edison recently went from four tiers to three, and I’m almost always in the .16/kWh tier even in the summer when my “net” usage for the month never goes above 500 kWh/month. I’m grandfathered on NEM 1.0 billing, which officially closed on 7/1/17 to new customers much to SCE’s delight. My system over-generates power in the spring, fall and a little bit in the winter. I consume the excess during the summer months.
The farther north you go, the more extreme the sun angles are in winter and summer. Instead of buying more panels that are installed at a fixed angle, maybe consider buying fewer but on a two, or even three axis mounting system. Gets more expensive but captures maximum solar winter and summer. But, how much property do you have, can you mount on the ground, etc,? If I was younger, I would certainly be looking at two or maybe three of the new Tesla Powerwalls (
Tesla Powerwall ) but I’ll probably die before the N. Koreans, Chinese, Russians take down the national grid or the apocalypse arrives.
I have a large property and mounted my fixed angled system on the ground at about 20º elevation. It would be well over 40º elev. up where you lived if you did a fixed angle. In addition to having the extra space for ground mounting, the panels are less expensive to service and clean. Panel maintenance hasn’t been an issue at all but ease of cleaning and cost is also a factor. My cleaning company charges $70 for washing and rinsing with DI water. Panels mounted on the ground are more efficient on hot days, when temperatures start to rise because you have ambient air ventilation on the underside of the panel. On the roof, you’re lucky if they’re a few inches off the hot asphalt or concrete tiles. Roof top temperatures can be 30º-50º warmer than the ambient ground temperatures.
Call your insurance company to talk about insuring your system or make sure it’s covered (generally under “other structures” clause). My system is covered for $50K beyond the replacement value of the house. If you mount on the roof, make sure your liability insurance would cover any worker that goes up there to service or clean them that isn’t covered with workers comp. Before signing any contracts make sure you see your chosen’s company insurance coverage documents, covering not only damage to your roof and home but also ALL workers for falls or injuries. There are lot of rogue, fly-by-night companies out there so read as many reviews (that you can believe). The market has weeded a lot of them out.
So my system is comprised of 24 LG MonoX (monocrystalline) panels. (Know what kind of silicon you’re being sold.) The system is rated at 6.6 kW. I used a 7.6 kW inverter, which allows for a little growth, maybe another four panels. My wife and I are empty nesters, we run the 5-ton air-con 24/7 for five months of the year in a 2,600 sq. ft house. Last month’s bill was a mandatory charge of $1.09 varies between $1-$9/month. The system was $28K installed. Got back $9K from fed and state tax credits, which came off the bottom line and is real money in your pocket via refunds the year after you install. I figure we saved $10K in power bills during last three years, so break even is about 36 months out. I'm ashamed to say I don't worry about leaving a light on here or there.
I’m sure there’s more to mention, and a lot of this doesn’t matter or apply to a system that is leased. Would I do it again? Hell yes, and if I was 30 years younger I would build my own house totally off the grid!
