It would probably increase my overall homemade power average about 5% to 10%. So to 85% to 90%. As much power as it takes to charge my EV to drive it about 1,200 miles per month (local driving charged at home), and even given the fact that that charging the EV is my most power consuming "appliance" for my home (even more than AC for the home in the summer and heating the home in the winter), there's still one very important fact about charging the EV. That's the fact that I usually can postpone charging until the sun comes out. I can't ever do that with my HVAC and water heater.
For example, in the past 366 days (leap day Feb 29 adds a day in my DB query report so that it pulls 366 days instead of 365 LOL) from May 15, 2023 to yesterday May 14, 2023, we consumed 21,366 kWh, with only 4,136 kWh having to be pulled from the grid. Thus, homemade power gave us 80.6% of our power.
Of the 21,366 kWh we consumed, 4,560 kWh of that was for charging the EV. That's to drive us 14,593 local miles (1,216/month average). Still, the 4,136 kWh for charging the EV is 19% of our overall power demand, which is large. But I don't have to charge the EV every day. The EV's range when charged to 80% is usually around 230 miles (more or less, depending on the weather and if we have to run the EV's AC or heat, and assuming local driving miles which has some highway 75mph driving). Since we average driving it about 50 mph per day, we can charge it to 230 miles on a good sunny day with free power, then charge it more on future days only if the power is free or if we drive it extra and have to charge it on the constant powered circuit (which may or may not be free, but is always powered). My wife asks for a floor of 120 miles range. So 230 mile range top to 120 floor = 110 miles we can drive the EV on bad weather days before we decide to put the EV on the constant powered charger. That's 3 days in a row of bad weather driving before charging the EV means charging it from the grid. I can't do that with my other major appliances like the HVAC or the water heater.
As it stands now, my main hurdle from being 100% energy independent is winter. In my December power statement, only 53% of my power use was homemade. January was 44% and February was 62%. And January was a low local driving month (about 150 miles charged at home). So I can't blame the EV for January being only 44% homemade power -- it's about running the HVAC a lot (a few nights we had single digit low temps) while getting little sun. Last winter looked similar, except the numbers moved to other months (depending on which month has the cold spells). The other months out of the year are over 80% homemade power. March was 84.8% and April was 95.8%. Looking at last year every non-winter month (not December - February) my homemade power ranged from the high 80's to high 90's with the lone exception being November being "only" 81.6% homemade power.
If I was to try to improve on that, my next step would be to take down the sheetrock from my walls and add insulation. And replace my windows with triple-paned windows. Then study the power throughput for a year to see if I need more solar or batteries or both. (Probably more solar, since I'm looking at some days in the winter that failed to charge the battery stack, with some of those days being multiple days in a row -- too many days to expect a battery stack to hold enough power to get through unless I made the battery stack ginormous to hold power from the prior week).
But if I was to go that far, I'd probably opt to downsize instead, something my wife and I will probably have to do one day anyway. I can have a house constructed to spec with better insulation and windows, and both the refrigerator and hybrid water heater closer to the HVAC so that the heat from the fridge can be sucked in more efficiently by the HVAC during winter months, and the cold air byproduct from the water heater can be sucked in during the warm months (more efficiently than what I have mine doing now, considering that the water heater is some distance from the HVAC).
I'd also need more inverter capacity for the very few times our home is using more than 18kW AC power (i.e. hard cold spell means HVAC using 10kW, while we're running the hot tub at maybe 4kW, while the dryer is running, etc.). That doesn't happen often. But since I never tell my wife that solar restricts her power needs and wants, it happens a few times.
Thanks for the time and effort, particularly winter issues and your location vs locations further North where winter conditions could be four to six months long.
As an aside the local electricity provider is building a large solar array to add to their renewable numbers in a State where such a build should be considered borderline insanity, if ROI was a consideration.
Give me a nice clean coal fired power plant any day to what some environmentalist falsely believes is possible from so called renewables. Especially in northern regions.