Sizing - Planning Stages

[kromc5]

Hello Everyone,

Me and my wife decided to leave corporate and take a new job taking care of ID individuals at home. While we enjoy the new job they do not understand power failures or turning anything off. We have installed water sensors and other devices to help but our usage is still high. We also buy foods in large bulk now due to prices greatly increasing and even added a new 25cft freezer last month. I cook 24 meals every 4 days to feed everyone and we would like to make sure the two fridges/freezers stay up. They also get upset over power outages since they do not understand the reason which is also a major reason for looking at solar/battery.

Off grid is certainly coming out much less expensive but the sizing calculators are all say 17-20kWh for our usage.
My original idea was
Growatt off grid 18kWh
Big Battery gen 2 8kw x2
CSUN 310W

I wanted to post and see if the math vs our usage is coming out correctly, I would appreciate any helpful feedback on sizing.
Also consider hybrid inverters but many are 3 times the cost or have very low kWh ratings.
Thank you

 

[snoobler]

Rounding.

Worst case is 3000kWh/month in Dec., that's 3000/30 = 100kWh/day. That's a LOT. I have a lot of those days in Phoenix in the summer... sometimes upwards of 120kWh.

Is your intention to power your entire place off-grid?

 

[kromc5]

That was the plan till I tried a few calculators and found my math was very much off. I suspect after further research I may just try to run both fridges and 2 freezers, 2 30 inch tvs, and hot water heater. Due to how the program works if we loose power we have to rent rooms for the ID individuals which is very tiring. If I could have as system that would allow us to at least run the hot water heater when needed, or run the stove to cook that would be a good compromise.

Thank you for the response.

 

[snoobler]

"Essential" backup systems are pretty common. There's some trickery that has to happen, but the items you're proposing are still very high drain.

You've pretty much identified the worst things except for HVAC. This isn't getting much easier.

The fridges/freezers likely use on the order of 8kWh/day unless they are uber efficient modern energy star devices, but you should be able to get the annual kWh use from the manufacturer.

A typical home water heater uses 4500W of 230VAC. Again, manufacturer should have average annual kWh usage. Powering hot water heater and the other listed items simultaneously will require a huge investment in inverters and batteries big enough to survive their use even for short duration.

You might consider instant hot water heaters at critical locations (bathrooms) that are propane powered that could be activated when the power goes out. Also, if you have the option of gas, converting to a natural gas water heater makes a lot of sense. Then you would only have to power the control circuits.

For backup, first consider power by the most energy dense source. Heat is best produced by fire. Electricity is best produced by a stream of electrons. Those come from solar panels, get stored in batteries and converter from one type to another relatively efficiently. Getting heat from electricity is also very efficient, but it takes a crapload of electrons to make heat.

What is an "ID" individual.

 

[kromc5]

"Essential" backup systems are pretty common. There's some trickery that has to happen, but the items you're proposing are still very high drain.

You've pretty much identified the worst things except for HVAC. This isn't getting much easier.

The fridges/freezers likely use on the order of 8kWh/day unless they are uber efficient modern energy star devices, but you should be able to get the annual kWh use from the manufacturer.

A typical home water heater uses 4500W of 230VAC. Again, manufacturer should have average annual kWh usage. Powering hot water heater and the other listed items simultaneously will require a huge investment in inverters and batteries big enough to survive their use even for short duration.

You might consider instant hot water heaters at critical locations (bathrooms) that are propane powered that could be activated when the power goes out. Also, if you have the option of gas, converting to a natural gas water heater makes a lot of sense. Then you would only have to power the control circuits.

For backup, first consider power by the most energy dense source. Heat is best produced by fire. Electricity is best produced by a stream of electrons. Those come from solar panels, get stored in batteries and converter from one type to another relatively efficiently. Getting heat from electricity is also very efficient, but it takes a crapload of electrons to make heat.

What is an "ID" individual.

ID refers to a person that is intellectually disabled, several states started a program where people that are ID can be moved from the institutions to homes where they have more of a normal life. But due to function capacities they do not understand power outages are get upset easily and do not do well in hotel settings. We had a drunk driver take out the transformer box on our street and was a difficult time. I named out street the drunk dump to do how may bottles of beer and liquor that are tossed out. The work is regarding but the gov has so many rules and regulations, not including keep a large amount of food on hand and water on hand. Even a minor outage has to be reported and and after two long power events we do not want to have to get hotel rooms again. I did purchase an inverter generator for the fridges/freezers and it has done a great job and performed well. The goal was to have backup power but when I research generac they were not very expensive but many reported very short run times on 500 gallons. I want to reduce dependency on the electric side as I believe things are not going to get better in the future with more outages and greatly increasing prices. On the hot water side I had to literately break the safety switches off in order to get the water below 110f, the current federal mandate is 120f for safety but the local gov wants it under 110f.

Thank you for the reply, seems like bigbattery so far is the best pricing for the storage side.

 

[snoobler]

Thank you for the clarification. I can completely understand why folks in that situation could be very unreasonable when most people could handle it. Good on you guys for doing the good work.