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OK, here ya go —

First some background -

1. Until I retired this August, I worked in a very technical field. I spent a LOT of time learning about the technology and the economics of residential solar prior to buying. I essentially told the sales guy “this is what I am buying.”

2. We have a fairly large home, about 4,000 sq feet so our total electrical needs are pretty high.

3. We live in GA and in GA the utilities at the time permitted a maximum of 10kW of production capacity - 34 panels for us at the time, given the wattage produced by the ‘latest’ panels at the time. 34 panels, 10kW produces about 70-75% of our annual power needs, with an asterisk I will explain.

4. GA rules on net metering (selling power back) meant we had NO illusion of “making money selling power back” and also our maximum generating capacity meant we would seldom be in an excess for a month anyways.

So why’d we go solar and what’s the benefits?

1. By producing roughly 70-75% of our own power, ie having our own generation capacity, means that by producing 70-75% of our power, 75% of our electric bill at current usage is FLAT RATE and insulated from increases from the utility. We OWN the power we produce. GA saw 30% increases after Biden was elected, so our increase overall was only about 10%. Hope that made sense.

2. We know that if we had to, we could easily cut our electrical consumption by 30% if we needed to, and produce ‘all’ our power from solar, but we prefer to live the way we want to. Point being we won’t have to face a $600 electric bill when we’re 80, unlike some of our neighbors. Ours can be closer to $300/mo. We chose to finance the system so yeah, we are paying for it for 25 years, but from a cash flow standpoint we are ‘robbing Peter to pay Paul’ - money that would have gone to our EMC bill instead is used to buy the solar system. KEY POINT: obviously solar systems don’t produce power at night, and less during the winter, so even if we did deliberately reduce consumption, we will still have a bill to pay due to nighttime consumption. This is where the battery comes in. Will cover that in a bit.

(REM: with the 30% increase in power prices, the solar system now DOES produce power at a lower cost than the utility sell it, but we did NOT start out that way, and we were well aware of it. WE went solar to flat rate the vast majority of our usage, a hedge against energy inflation. THAT has emerged as a wise decision)

SO about the battery. Think of the battery as a solid state generator, but one you use EVERY DAY/NIGHT. You can forego the battery and just get a Generac, but it’s a LOUSY investment vs a battery because you SELDOM use it. Although they work REALLY well when you do need it. So honestly it’s a trade off between solar batteries and a generator. Let’s get into this a bit deeper.

Every day the sun shines, then panels run the house and charge the battery. AS the sun sets the panels stop producing, and the battery discharges and powers *some* of your house ... until it has discharged to a minimum percentage you select. Operationally, you don’t want to discharge the battery to “zero” in case you DO have an outage and want to use the battery to power the house. We set our minimum to 50% so that in the event of an outage, our battery can run ‘all night’ to power specific circuits - until the sun rises the next day.

Also please think of a battery as a bathtub full of electricity. This is key to understanding what your battery *CAN* do for you. Using the bathtub analogy, let’s say your battery can hold 10 kilowatt hours of electricity. That means in theory it can supply 1 kilowatt of power for 10 hours. BUT ya gotta understand the maximum amperage (rate and flow of electricity) it can discharge, analogous to the size of the drain— how fast can the bathtub drain. For example we have a smallish 10 kWh battery (I’ll explain why) that therefore holds 10 kilowatt hours of electricity, and it can sustain a discharge rate of 34 AMPS at 110V. Our size battery is NOT sized to run 240V circuits. *IF* we had bought a 20kWh battery system with a 68 amp discharge rate then it *could* run 240V circuits, but only until the ‘bathtub’ was empty. In other words, ya ain’t running the oven and cooking a turkey. You CAN however run a modest 240V HVAC system overnight. It is ESSENTIAL you think about what circuits and devices *MUST* operate when on battery backup and design/buy the battery that’ll do the job for you. For us the 10kWh smallish battery, with 34 AMP service, will run 16 select circuits - the fridges and freezers, the air handler for the gas heat, the master bedroom, the kitchen outlets, (including the microwave) the master bath - BUT NO heat pumps, not the oven, NOT the water heaters. Our house has two heat pumps and a gas/AC unit. WE also have a gas range. With this setup we’d keep all our food safe, be able to cook sufficiently, be warm in the master and kitchen. WE also have three fireplaces, one with a circulating fan the battery can run just fine. No hot water from the tap, and no AC except for ‘emergency’ window units we keep in storage and run every once in a while. And no baked goods, except what can be baked on the 110V toaster oven. This is what it’s like for us to run on battery-only. Best to wait til the sun comes back up and shines brightly, eh? ;-)

We have neighbors with a bigger house and a REQUIREMENT to run the HVAC in the master off battery. They have a 20 kWh battery which holds twice as much power and can discharge at 240V, 50 amps — easily running the HVAC in their master. Plus all the essential circuits for fridges, master suite and bath, kitchen etc. Their system is 55 panels + the 20kWh battery.

SO to net out the benefits of the battery:
1. It stores electricity by day and discharges a set portion of it EVERY NIGHT, reducing your electric bill every night.
2. In the event of an outage, it’ll keep stuff running til the sun comes back up, and then the sun powers the house (or most of it in our case) and charges the battery for the next night, and so on and so on. We can withstand an extended outage this way, and never run out of fuel for a Generac. Thus the battery is a SILENT solid state battery.

Just know that batteries are an EXPENSE item, just like buying a Generac. They COST you money, but they provide you the assurance of 24 hour power ‘forever’, and do so silently. AND you get use out of them every day. A Generac means you will run out of fuel eventually.

Finally, because of where we live (rural north GA) and what we are prepared for, we have the solar system plus battery, PLUS a gasoline 5800 Watt generator and a tertiary 1800 Watt dual fuel generator. We also have a small off-grid solar system for the greenhouse that has modest capacity compared to the home system, but COULD be employed for other tasks in a worst-case scenario.

NET: we were realistic about solar going in, it has exceeded our expectations, and we would do it again if needed. Also in retrospect, we should have gone with a 20 kWh battery (it can still be added) for the convenience of powering more circuits on battery, but initial economics drove a different decision.

Ping me with any questions.