We’ve had our solar panels operating for more than a year now. So far they’ve required no effort to maintain and after we built up a surplus of power exported over the spring, we haven’t had any electricity bills over the minimum connection charge. It all just works. I’ve put together a pair of graphs from our PECO bills.
This first graph shows our net electricity usage, note the date listed is when we were billed, so the electricity usage indicated is from the previous month. In the year we had 4 months where we used more electricity than we produced – the two darker months near the winter solstice and the two warmer summer months closer the fall equinox. Over the course of the year, we’ve used less electricity than we produced, although it should be kept in mind this doesn’t include natural gas for our furnace (everything but our HVAC is electric). So we’re not yet carbon neutral.
When we installed the solar panels, we also installed a single Tesla Powerwall battery. The battery has been set to discharge up to 50% under normal operation (it also operates when the power goes out). This graph shows the fraction of energy drawn from the grid in 2022 compared to 2021 (this does not include electricity exported in 2022, this is not net energy use in 2022 like the first graph, its only the imported amount). If we let the Powerwall discharge further, we could probably cover our energy use at least half the year, but it likely wouldn’t be sufficient at the end of summer or during the winter months for us to go completely off-grid. More battery capacity wouldn’t be sufficient, because as the first graph showed, we don’t generate enough electricity those months.