4 ms·

48h is less than 5 kWh of batteries, one quarter of what the parent post proposed as the absolute minimum.

• Syonyk 5y ago
  It will depend somewhat on the area, and you can trade panel area for battery pack capacity to a reasonable extent - but you either need a lot of panel area to power you on dark days, or you need a lot of battery to ride through those periods. Out here, at least, we'll have a week where my 5kW of panel on my office produces less than 1kWh/day, often rather significantly less. The problem is that after 48h, then... what do you have? You need to have either enough panel area to both run loads and charge the batteries, often in dim conditions, or you need a lot more battery. Doing reliable off grid power takes a lot more than most people who haven't dealt with it assume, especially if you're dealing with serious winters and don't want to light a generator. I'm basing my estimates off what it would require for me to run 2.4kWh/day, year round, without generator, on my office system - and it takes a LOT. I have 5kW of panel, 10kWh of battery, a typical winter day load of around 3kWh (base loads + minimal compute loads for a work day), and I still require a couple gallons a year of gas to run this reliably. Depending on the winter, I go through 3-5 gallons of propane for heat as well, though I've been trying to move to kerosene - more efficient, as I can run a lantern as a combined heat/light plant on my desk, and heat my hands, which are the only real constraint on cold temperature work in there. I know those numbers sound somewhat nonsensical for a 100W load, but I literally make a living in an off-grid office...