UPS Backup - Basically a generator backup

[martinman]

I'd like to build a battery backup system that essentially replaces a generator system for use during power outages and emergencies. The solution i've gotten quoted are for critical load which are very costly. About $40k+ for 14kWH system (battery, solar, inverter, install, etc.) -- my average monthly consumption is ~28kWH here in Michigan.

I'd like to build a DIY system that:

Must have (for emergency / power outage use)
* can run kitchen (new refrigerator, 5-6 outlets, LED lights, stove (gas))
* can run Deep freeze in the basement
* can run Furnace (which we just had replaced this year -- 220)
* can run computer / laptop / network / charging stations
* Can be charged by the grid during "normal" times
* Can charge via modular solar panels that I can setup if out more than 24 hours.

Nice to have:
* Maybe a few outlets in entertainment area.
* Will last atleast 24 hours with nominal use.
* Can automatically swap back and forth when power goes out.

14kWH is probably way overkill for me right now. So, i'd like to start small and grow into a system. Maybe buy 1 battery with the ability to add more down the road.

Is this a feasible use for solar/battery? Or should I just go buy a gas powered generator, skip the furnace, and buy a modular heater?

 

[BentleyJ]

To adequately address your question, the electrical consumption information you posted above needs some clarification. You monthly average is certainly NOT 28kWh since that would be less than 1kWh per day. Please include the following.
Avg. MONTHLY electrical usage, for both winter and summer.
PEAK electrical usage in kW & do you have any inductive motor loads like an AC Condenser or well pump.

 

[Hedges]

You can wire a "generator" inlet to your breaker panel, interlocked to main breaker with 120/240V 30A recessed plug.
That would let you hook up a portable generator, or a battery/inverter. You manually turn off excessive loads like furnace.

There is a range of sizes of inverter/battery, and some PV panels can extend run time. All-in-one "generators" with batteries and inverter are available from Costco and elsewhere. Good for phone/internet, maybe refrigerator for a day or so. Larger inverters and batteries can get into big bucks and can power window or central A/C, but should have enough PV to keep them going.

As Bentley says, you need to determine your loads. Max continuous kW, motor starting surge kW, total kWh/day.

PV is a good investment if all the power is used for a number of years. Batteries are becoming competitive. But neither makes financial sense or half a dozen brief outages per year, except small and just powering communication gear (where data is more important than paying $2/kWh for a small amount of power.) So many people to grid-tie PV, if they have net-metering available. Backup capability adds cost, but PV pays for itself.

"Modular heater"?
Just avoid issues with carbon monoxide and fire hazards.

Running heater fan is feasible. Running electric heater is not, except by generator. Gas water heater with water loop to radiator might be good.

 

[martinman]

@BentleyJ : Good catch, I mis typed. I was looking at my monthly DTE bill and mixed things up -- my *daily* use is 28kWh with critical load estimated at 1/2 of that.

Would I be better off with a ecoflow or blutti and pull it out when needed? Otherwise, a 48v LiFePower4 and growwatt would be similar in price, but I'd get way more capacity with the DIY approach.

 

[Hedges]

Any packaged solution or small battery will provide you as much power as the battery holds. Have you determined if that gives you enough run hours? I think it could make your morning coffee and keep the internet on, but likely not run furnace blower during an extended outage. In other words, it will last through an outage where you could have just used candles for illumination and otherwise "roughed it".

Large expensive battery bank, or large somewhat less expensive PV array, would get you through longer outage.
Generator with propane (never goes bad) would be lower cost way to power furnace blower or A/C for occasional use.

 

[MiSh]

I'd like to build a battery backup system that essentially replaces a generator system for use during power outages and emergencies. The solution i've gotten quoted are for critical load which are very costly. About $40k+ for 14kWH system (battery, solar, inverter, install, etc.) -- my average monthly consumption is ~28kWH here in Michigan.

I'd like to build a DIY system that:

Must have (for emergency / power outage use)
* can run kitchen (new refrigerator, 5-6 outlets, LED lights, stove (gas))
* can run Deep freeze in the basement
* can run Furnace (which we just had replaced this year -- 220)
* can run computer / laptop / network / charging stations
* Can be charged by the grid during "normal" times
* Can charge via modular solar panels that I can setup if out more than 24 hours.

Nice to have:
* Maybe a few outlets in entertainment area.
* Will last atleast 24 hours with nominal use.
* Can automatically swap back and forth when power goes out.

14kWH is probably way overkill for me right now. So, i'd like to start small and grow into a system. Maybe buy 1 battery with the ability to add more down the road.

Is this a feasible use for solar/battery? Or should I just go buy a gas powered generator, skip the furnace, and buy a modular heater?

Another question is how big is your budget? You stated $40,000 is too much. Is $20,000 doable? $10,000? If you want to put in the time and effort I'm sure you could build something very nice, including lithium batteries, for 10-15 grand that will back up your required loads for at least a day or more. I wanted almost the exact same things you did and got so hooked on research and learning about solar that I built everything myself and became addicted! It's now my hobby. I love anything involving being self sufficient and solar related.

 

[martinman]

I'd like to grow into something by starting as cheap as possible (but with high quality components). A battery for $2k and inverter combo $1k -- maybe add some panels $1k, then a contractor for aspects of grid charging and planning. I'm just getting started, but in my head I think i can build something capable for between $3k-$5k.

 

[ePowerBank]

Hello @martinman. I'm also in Michigan, and like some, interested more in power backup than daily solar. I'm surprised you didn't have Sump Pump in your listed backup items. Below is my DIY approach which I think you may have a hard time finding for cheaper.

I'm about 1/2 way through a DIY setup which includes:
- Two NG generators (240V), about 3KW ea for NG rating ($1600)
- Sungold 6KW 48V inverter (UL listed) ($1100)
- Signature Solar EG4-LiFePo4 48V 100AH 5.1KWh battery (one for now) ($1500)
- Interlock switch (main panel) IMPORTANT
- Sense power monitoring ($250)
- Upgraded gas meter (~$300)
- NG manifold with Quick Connects & 3/4" Flex Lines (~$500)
- NG Conversion kits for generators (~ $400)
Total DIY cost approx $6000

I figure the 5KWh battery is just enough to get me through an evening of running a few LED lights and a bit of HVAC heater as well as 3 fridges, if I don't want the noisy generator running all night. It will be easy I figure to add another battery down the road if need be. Like you, I'm about 30kwh per day, and roughly 10kwh during evening in winter, could get by with less I think.

I used a product called Sense to monitor my power usage, not to hard to install and very informative for monitoring or managing power consumption. Even has $50 extra sensor option to monitor backup or solar power scenarios.

For my setup I have what I call active (automatic) backup for my sump pump, and passive (manual) backup for the house.
The key to my setup is that the Inverter and Generator(s) needed to be 240v (split phase) so I could feed both legs of my panel. I have a fully finished basement which includes a sub panel, so combined I have about 50 breakers with 2 panels have distance between them, hence, I don't like the Critical Load box solution. I also installed some $100 UPS units that my IT and satellite routers plug into, along with a higher end TV. No losing Wifi with a silly 1 minute outage.

I have option to run 1 generator for less fuel, or both if it's needed, not to mention MUCH quieter and they're NG. I needed to upgrade my NG meter and added a manifold in the garage with a couple of quick disconnects. In all, I think it would be hard to have this much back up for the $$. I also like option that I can take this with me if I move. And, owning additional properties it's nice to know the open frame generators are someone portable at about 100lbs ea.

Check out my plan here... let me know if there's any questions.