220v connected to solar-battery-inverter

quiquequique Solar Expert Posts: 252 ✭✭
I'm almost sure what the answer will be but I'll ask anyway:

Is it common practice to connect any of the big 220v powerhogs (A/C, water heater, clothes dryer, electric stove) to a battery fed inverter system?

I've always told my clients no because of the cost of the battery bank and inverter as well as solar panels. I've also just told them to replace:

Electric heater with a solar one
Electric stove with a gas one
A/c with a solar one
Clothes dryer with a clothes line :)


  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: 220v connected to solar-battery-inverter


    See? You were right! :D

    First you'd need an inverter capable of 240 VAC (XW, Radian, etc.). Then you'd need to be able to accommodate the Watts (water heater = 3500 Watts, stove = 12,000 Watts). Then you need batteries enough to handle the current and Watt hours without going flat in an instant.

    Not to say that it isn't possible (ChrisOlsen has a whole electric house off-grid) but it's not the cheapest/easiest way to go.
  • BB.BB. Super Moderators, Administrators Posts: 32,007 admin
    Re: 220v connected to solar-battery-inverter

    And "it depends" is also a good answer... The newer Mini-Split AC/Heat pump systems with the "inverter" controller have been seen to regulate very nicely down to 300 watts start-up/steady state (of course, that is on low heat/cool settings). But if you run 300 watts all "day" long, you can have a pretty nice cool (or warm) home when you get there in the evening. There are some threads here where people are running the old Sanyo units in heat pump mode with snow on the ground (pretty amazing).

    Similar with the new Heat Pump Water heaters--They are ~2-3x more energy efficient than resistive water heaters (the hotter the ambient, the more efficient the heat pump). We have at least on poster here with a GE Geospring water heater that he sets to heat pump mode only (takes ~500 watts) (there is a backup resistive heater) and it works very well for his needs (small household as I remember).

    So--Even for "smaller" battery based systems, these units appear to be giving propane/grid electricity a run for their money... Even solar thermal water heating systems are having a hard time bettering the cost/benefit ratio of solar PV + heat pump house/water heating.

    So--less black and white... More gray to the picture.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: 220v connected to solar-battery-inverter

    To run an electric water heater, and especially a stove, would require a HUGE off grid solar system. Now if your client has just won the million dollar lottery, then they might be looking for a place to blow their winnings, but other than that? Nope.
  • RandomJoeRandomJoe Solar Expert Posts: 472 ✭✭✭
    Re: 220v connected to solar-battery-inverter

    Don't run the main house AC off-grid, but I do have a mini-split AC unit (9000 BTU) that I run off-grid. I have 2000W in panels, and can *just* run the mini-split along with my usual afternoon loads on sunny days. Won't cool the entire 1700 sq ft house by any means but keeps my office comfortable even on 100+ days, and a strategically placed fan can help temper other areas a bit. (I'm on the utility company's variable-rate plan during June-Sept so keep the main AC off 2-7PM no matter what.)

    I'd LOVE to get one of the inverter heat pump mini-splits so I could run cooling over a longer portion of the day (like right now - had to turn off the mini-split since I can't produce 1500W in late afternoon - but could easily keep the inverter unit going at 600W or so for a while longer) as well as use it in heating mode in winter. Just haven't convinced myself it's worthwhile though. I don't have any cost-justification for it in my setting! Maybe when the current unit dies, but when I have plans like that the "current" item usually lasts forever... :D
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