Typical last mile battery runtime (protecting against power cuts)

Sun Feb 5 06:56:06 UTC 2023

On 2/4/2023 9:31 PM, Mark Tinka wrote:
>
>
> On 2/5/23 07:02, Roy wrote:
>
>>
>> My all electric house is in a rural area.  The generator that came 
>> with the place is a 20KW Onan,  The bad news is in can't handle the 
>> house.  I think it is the Aux Heat on the heat pump that is the 
>> problem.  I have to also power the well pump and the septic pump.
>
> Is your house single or 3-phase?

Single phase.  The house is 200A service and the barn is another 200A 
service

>
> I'd be curious how much horsepower your well and septic pumps require. 
> The most I've seen is 15hp @ 11kW, but that is pretty massive for an 
> average home, even an off-grid one. Typical requirements would be in 
> 0.75kW - 5kW range, which is a wide range.
>
> Do you know how much power the heat pump requires?

I don't know how much the pumps require.  The water well is about 100 
feet from the house and the pressure tank.

The septic pump has to pump uphill to the drainage field.  Distance is 
about 250 feet and elevation gain of 100 feet or so.

The heat pump doesn't seem to be a problem but the aux heat is on two 
20amp 220v circuits.   There is a switch on the fan enclosure to disable 
the aux heat.

Another biggie is the electric hot water heater.

On 1/30 it never broke 32 degrees and the house used 145KWHR (average 
was 6KWH).  Thank goodness I am not far from the Columbia River and the 
BPA has a major substation about 5 miles away so I pay less than 10 
cents per KWH

Over 2022, I lost power about 8 times.  The longest outage was 15 hours.

>
> I'd struggle to see how a 20kW generator struggles to to run a home, 
> unless you've also got heated floors, saunas, steam baths, water and 
> space heaters, electric stoves and ovens all running at the same time 
> :-).
>
> Mark.