Experimenting with Solar PV
Prompted by a telemarketing call I talked to the sales rep and updated some notes on home solar power systems.
What they were offering seemed reasonable, maybe very slightly higher than you could find by shopping around, but they offered a 40 month payment plan.
For more detail see this page.
I have recently added 2 panels and have been watching the output. We’ve had fine, overcast and rain in that time.
I’m still thinking that to seriously go solar you need at least 6x your daily average KWh use in solar. So for 1KWh average consumption (24KWh per day), you need at least 6KW of solar capacity. Our roof area facing north-ish is large enough for about 4KW.
I’m still not sure about battery capacity but would lean towards at least 5 days of capacity, x2 would be best because you shouldn’t discharge below 50% if using lead-acid batteries. That’s a lot of battery, maybe 120KWh – the biggest and most expensive part of the system.
Staying grid-tied means you can top-up from the grid. Many grid-tied systems don’t have battery storage, so they have to sell excess KWh units back to the grid usually at a low rate or loose them, which all extends the cost recovery period. If there is no load on a solar system, there is no generation and no cost recovery. From what I’ve seen, grid-tied systems with batteries, may not provide power when the grid is out because they are not allowed to back-feed the grid. So, for most people who go to work during the day and use power morning and evening, I think the low-end grid tied solar is a bad investment.