Not sure where you live but we can get by on 14.5kw/h per day including two fridges, security systems etc.
We run a 10kw system and it would be a rare day we get less than 15 kWh out of it, seeing as that is 1.5 hours at full load. 30 - 40 kw is more typical, peaking out around 60kw.
That is *very* good data to have, thank you. So on an average day you get about 4 solar hours of light, with a peak of 6 solar hours of light. That matches my observed values here with a much smaller system (~1kw) on a grid-tie/battery reserve.
I've noticed the fridges are the big power pullers (aside from AC, which in a disaster I am not running) not because they pull a lot of juice but because they pretty much always pull it. I should put a Kill-a-watt on the fridge again and see just how much power it pulls in a day, in fact I think I'll do that after measuring the idle current of Antminers (for another thread).
How big is your battery array? Mine currently is 200ah*24v or 4.8kw total. My solar array is about 1.2kw total (single crystal panels so pretty efficient) and my inverter right now is a 700 watt UPS converted to run on external batteries with a Matrix/5000 that can be used if I needed a really high drain load.
If I'm running my house in emergency mode it's about 4kw a day of power used. Which is on the edge for my system: Given I can only generate about 4kw of power a day with the panels I can run for a day with no solar power and even then it would be difficult for me to "catch up" and charge the batteries to 100% with solar alone.
My secret weapon for that is the car: A 1kw 12v battery inverter attached to a car can charge the batteries to full in a couple of hours. Having a hybrid in this case is *really* cool, as you can charge off the hybrid battery and the engine only has to fire up to charge the hybrid pack (which it can do quickly and more efficiently than running 100% just to spin the alternator). A bonus is you have a 10-20 gallon rolling fuel tank that you can also drive (at 40mpg) somewhere to tank up on fuel if needed.
So as long as civilization doesn't completely puke I'm ok. Really. Interesting. Stuff.
Yes in an emergency we would loose the beer fridge, which should significantly reduce our load. As you point out, aircon is the real killer. Our system draws at least 6kw so would be a definite no.
A key is not to fully optimize your panels, don’t point them all due South because that will give you a weak feed on the shoulder periods and a big spike in the middle of the day when you just have to dump it on the grid.
Instead you want 1/3 pointing south east and 1/3 pointing south west and 1/3 south. This allows you to pick up the early morning sun and the late afternoon sun which is much more valuable than the midday sun.
Battery is a Tesla Powerwall 2 with 13.5 kWh with 5% capacity reserved for intermittent grid trips - it comes on in less than a second. Sometimes you actually get more than 13.5 out of it in a day if there is a storm and you draw down and then recharge in the afternoon
Other days it doesn’t get a full charge if it is cloudy and we are running the aircon non-stop - household consumption can peak around 70kw/h per day which exceeds panel capacity even in full sun if we abuse aircon, run the stove, dishwasher, clothes dryer.
Panels cost very little these days, they seem to be halving in price every five years. If you put your system in awhile ago, you might try and see if you can economically add more panels. Of course you will need a converter but if your string inverter doesn’t have enough capacity you could consider adding microinverters which allow you to add panels piecemeal.
You are right about the car but I am more worried about fuel security than power security. We still don’t have an electric car yet and we can’t produce our own fuel. I possibly should go get some fuel canisters but don’t like the idea of storing them in the garage.
Edit: just checked the numbers. Our minimum production in a month was 792kwh and max was 1560kwh. So production doubles in summer.
