As long as I produce as much as I consume during the course of a month, I'm only paying the power company $32/month for the base meter charge.
So if I consume say 200 kWh a day (which would be a constant draw of 8,333 Watts, enough to power 90 1660Tis 24/7), then my monthly power bill would only be $32 and I would not have to mess with batteries and their associated maintenance cost. Of course in order to keep the power bill at $32/month, I would also need to produce an average of 200 kWh per day. On cloudy days and during the winter I would produce less, so during months where that was the case, I'll have to pay the shortage at a rate of $0.12.
Still, if my average production is only say 100 kWh, I would have to pay the power company for the other 100 kWh, and my net kWh rate would be $0.06 which, while not free, it still pretty good.
My long term plan is to continue to add solar panels that are grid tied, until I reach a point where I can leave all my rigs running 24/7 and only pay the power company $32/month since I will produce as much as I consume. If I turn on all my rigs and ASICs, I draw 20,000 watts, which is 480 kWh a day. At $0.12 per kWh, that works out to about $58/day, or about $1,730/month. I was doing that for many months back in the 2nd half of 2017 and the beginning of 2018. It was not a problem since I was earning as much as $500/day and the power cost only represented a little more than 10% of that.
Fortunately solar panels continue to drop in price. Right now I can get 360 Watt 72 cell panels for $170 each, which is $0.47 per watt. In quantity, the cost goes down to about $150 a panel, or $0.42 per watt.
String inverters run about $0.10 per watt. Racking is about $0.20 per watt, so the grand total comes to around $0.75 per watt. So a 100,000 watt system would cost about $75,000 in material if you do all the installation work yourself.
Once you start getting past 50,000 watts or so, you are going to run into issues with a residential grid tied system unless you ensure you always have enough miners running to keep the power you push back into the grid below, say 20,000 watts. I did have the POCO upgrade my transformer from a 25 kW unit to a 50 kW unit last year, so I'm good for now, but as I expand towards a 100 kW system there will be trouble if my Internet connection went down for example and all my rigs went idle. But I'll worry about those issues when the times come.