A little background

First I am not a professional, I have not been certified in any way. Everything I’m saying is based on reading, watching, and messing around. I did have a class in High School on electronics that included a module on home wiring in the late 70s, I graduated High School in 1980, so that should put that in some perspective. 

I first ventured into home power backup as a reaction to the 2012 derecho that caused an extended 7 day blackout. At the time I thought I was well prepared because I had many UPS systems in the house and could power computer, charge phones, and run internet connection for short intervals allowing us to remain connected to the world. What I learned from this event was UPS systems are useful but will not help if the system up stream also loose power for more then 24 hours. The ISP (Comcast at the time) didn’t have backup for its nodes of the network. Cell towers don’t stay up and so all the modern communications stuff become bricks even if you have local power. Nothing I’m discussing here solves the communication issue but it will keep the fridge cold and the house comfortable.

Generator

My first bite at the apple was a generator, manual transfer switch, and an external generator inlet on the outside of the house. This would allow me to select critical circuits, refrigeration, lighting, communications, portable heat, and fans to power for as long as the fuel lasts. I selected an Liquid Propane (LP) generator at the time because LP doesn’t age like gas and I don’t have to rotate the fuel regularly. I know me and know that would not get done like it should. I wired a generator inlet from the back of the house to the transfer switch and wired 8 critical circuits into the transfer switch. We have not had occasion to make use of this for more than an hour since setting it up. 

Rooftop Solar

In 2019 we installed 9.5KW of grid tied rooftop solar. Grid tied rooftop solar is not useful in a power outage. The solar inverter will only provide power if the gird is active exporting any power not used at the house. The rooftop solar only reduces the amount of electricity that we import from PEPCO.

Whole House Battery

In 2025 we installed an EcoFlow Ultra Delta Pro X (DPUX) inverter/battery system with 24KWh of battery storage and a Smart Home Panel 3 (SHP3). I added 3.25KW of solar to the DPUX system with “portable” panels setup in the back yard. The DPUX in combination with the SHP3 provide 20 millisecond switch from Grid to Battery for the whole house in the event of a power outage. The SHP3 replaced my homes original main electrical panel. This also retired the manual transfer switch. 20 millisecond is fast, and fast enough for most household items. However my FIOS fiber interface would reboot when the house switches from Grid to battery or back so I have retained my UPS systems for computer and Audio Visual equipment as a buffer. 

What does the EcoFlow setup get me that I didn’t have before. 

• Automatic switch from Grid to Battery
• Whole house. I can prioritize circuits in the configuration of the SHP3 and I can turn circuits off and home with the app on my phone.

• The batteries can charge from rooftop solar (when the grid is up), backyard solar (independent of the grid), my generator, or the grid.

  

Power arbitrage

As a result of having solar we have time of use rates from Pepco. There are three different rates from Pepco, on-peak, int-peak, and off peak. The times very in winter and summer, but what the battery lets me do is minimize on-peak, and int-peak electrical import from Pepco. This small savings adds 

up over time and can produce a return on investment that pays off the EcoFlow system in 5 to 7 years. Any Pepco customer can get time of use rates you don’t have to have solar.

About Our House

My house was built in 1970 and is 1750 square feet of conditioned interior space. We do not have gas in the neighborhood so heating is by electricity or fireplace only. We also upgraded our HVAC to a Geothermal Heat Pump which normally only pulls a maximum of 1300 watts unless it is using the emergency backup power. Our water heater is a hybrid unit independent of the Geothermal. We have two electric cars one charges at 7.9KW and the other 11KW. I have derated the wall chargers to 7.9KW since the DPUX supports a max of 12KW and can easily be over drawn if something else is on while the 11KW car is charging. I don’t normally charge the cars on the DPUX, but have experimented with charging during the day to push excess solar into the car rather than importing everything from the grid. I also schedule the cars to charge in a standard interval so they are rarely both charging at the same time. 

Starting From Scratch

My current thinking is to go hybrid. Start with battery inverter setup that can power your home. Focus on the inverter and transfer switch capacity first. I favor something like the Smart Home Panel 3 from EcoFlow. There are other brands but I like the modular battery that I can upgrade without calling an electrician. 

Options:

• Generator circuit with service lockout and external generator inlet.
• Manual transfer switch with selected emergency circuits external generator inlet or internal.
• Smart panel with battery backup, automatic transfer switch.
• Whole house generator with automatic transfer switch