# Question about solar DC to AC amps

New UserPosts: 11Registered Users
I'm just doing some research and wanted to know about the amperage transfer.

Lets say I wanted to go 100% off grid

That my old service was 200 amp 240/120v from grid

That my photovoltaic/Wind was 48v

Now If I went with a pure sign wave inverter/inverters to equal my old 200 amp service @240/120
And that somehow "not likely tho" that I drew close to the 200 amp AC what would
the DC amperage be at that point in time??

Dom

• Super Moderator Posts: 5,070Super Moderators
Re: Question about solar DC to AC amps

240 volt * 200 amps =48,000 watts
48,000 watts @ 48 volts= 1000 amps.

The equation always stays the same, regardless whether it's ac or dc.

V*A=Watts

W/A=V

The idea of a 48 KW inverter set for a residential application boggles my mind.

The reality is that I would suspect unless you have electric heat or lots of A/C loads you would rarely use more than ~1/2 of the ampacity of the panel, say 24 kws.

Tony
• Solar Shotgun Posts: 10,309Solar Expert ✭✭
Re: Question about solar DC to AC amps

it's even more mind boggling to store any power in batteries for the times solar or wind isn't present in order to maintain said 200a service. it is actually rare that people approach the full service rating and even if they have popped the main breaker a few times, the power that is normally drawn is by far much lower than that. anybody that draws that much consistently needs to do the number one requirement for renewables and that would be to learn how to conserve power. it's far easier and cheaper to save a watt than create it.
• New User Posts: 11Registered Users
Re: Question about solar DC to AC amps

I thank you both for the reply Like I said it was just for my knowledge
I know for a fact I don't use anywhere near the 200 amps.

And yes agreed cheaper to conserve than to make and that's what we do.

I was just having a huge brain fart from the DC to AC knew it was 48000W on the AC side just couldn't figure out the DC side lol.

Once again many thinks for the help/jump start of my brain
• New User Posts: 1,280Solar Expert
Re: Question about solar DC to AC amps

200 amp service does not mean you will use a sustained 200 amps.

If you want to totally replace grid you have to meet the peak requirements and average power consumption (at your highest consumption time period.)

In my case, in Florida, the killer is central air conditioner. July through September it accounts for 55%-60% (>30kW-Hrs per day) of my monthly consumption. My central A/C, when running draws 3800 watts. 500 watts is air handler (blower), 3300 watts is compression and condenser fan. My programmable thermostat shows it runs between 8 to 9 hours a day during the summer with highest duty cycle between 3 pm and 6 pm.

I measured the start current on the compressor with closed loop hall-effect sensor. I was blown away to find it draws 120 amps rms from 240vac. Startup last for 400 msecs. I have two SW5548plus's series connected that runs the A/C. I have two SW4048's that run the rest of house.

You can put a little artifical intelligence into load management. For example, do some load sheading when A/C request startup. Knock off range or hot water heater (assuming electric). A little of load management can go a long way to cut down peak load current.
• New User Posts: 814Solar Expert
Re: Question about solar DC to AC amps

I look at the figures give on many of these posts from USA and see that it appears a normal house has a input capability of 200 amps .. at 110v???
Here in Australia your inlet to house has a 50amp fuse and we only have 240 v.. but change that to your 110v and its still only about 120 amps..
But have never in all my life myself known of it or any friend that has found that inadequate.

We have a general store(small) connected to our house and use total 600kwh a month thats a bit more than many friends I know use.
We have 2 large refrigerators 5 small freezers 1 large chest freezer 400w projector TV. used about 3 hrs most days.
No lightinng is grid supplied as it is solely provided by solar power. but only runs to total load about 200w.
No AC but ceiling fans on a lot of day and night.
• Just some guy Posts: 23,909Super Moderators admin
Re: Question about solar DC to AC amps

Actually, the typical north American home is 120/240 Split Phase 60 Hz AC (or 117/234 VAC)... Think a center tapped 240 VAC transformer. 240 across the outer two taps. 120 VAC between each outer to center tap.

Older homes (built in the 1950's--like my parents' home) where 30 amp 120/240 VAC. 125 amp and 200 amp services seem to be common now (I am not an electrician):

30 amp * 120v = 3,600 watts per phase (2 phases)
30 amp * 240v = 7,200 watts (older home)
125 amp * 240v = 30,000 watts
200 amp * 240v = 48,000 watts

Of course you cannot use maximum power--NEC (National Electric Code) only allows 80% of rated power. And it is unlikely that all of the loads will add up to nameplate rating of the service panel (excluding starting surges for motors, etc.).

In a temperate climate--it is pretty easy to run relatively low electrical usage... Our family tries to be somewhat energy efficient (read "cheap") and we average around 200-250 kWhrs per month (family of four, natural gas for heating/cooking/hot water/etc.).

The typical American Energy Star rated fridge/freezer is probably around 30-60 kWhrs per month. The older ones could have been 5x that amount (some of this stuff has really been improved).

Through in A/C and Electric Heating--1,500-2,500+ kWhrs per month seems to be normal.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• New User Posts: 1,280Solar Expert
Re: Question about solar DC to AC amps

U.S.A., country of conspicuous consumption.

While visiting the Carribbean islands, I noticed the houses had #10 wires coming in from the power poles.

Here in U.S. its #00 or larger. 150A @ 240 vac is usually minimum these days.
• Just some guy Posts: 23,909Super Moderators admin
Re: Question about solar DC to AC amps

I don't know... We have already talked about / seen residential 3 phase power from Poland, and 3 phase 40 amp x 400 volt = 48,000 watt service from Norway...

I guarantee my machinist friend would have loved to have three phase in his home for use in his home machine shop.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset