This. I had this grand plan to convert (almost) everything to electric and then install solar but it would take roughly 16 years to pay back the solar install based on our current electricity bill. Then I’ve tried to rationalize it based on added resale value, which, where we’re located, might command a small premium to the install price, but even that seems questionable and we don’t have any plan to move.
It seems like there are two justifications for solar if you’re on the grid. Either you want to do right by the environment (totally good, though very pricey, reason to do it!) or your electricity costs are very high. If there are others I’d love to understand them. Maybe if you’re a prepper (not making fun) then that’s another reason.
Someone on a forum I'm on has a solar setup because they have poor grid reliability. Solar + battery + transfer switch provides them with good availability.
It's way easier to capacity plan with a fuel based generator though. My 35kW generator can go at least several days on a 500 gal propane tank, regardless of weather. Potentially indefinitely if propane delivery is available, but I lose phone service when the power is out beyond 4 hours, so I'd have to venture out to get signal to call, and if power is out for more than a few days, the weather is probably pretty bad and delivery may not be available.
With a solar + battery system, handling potential multiday outages, I'd be concerned about my winter where there's less than 9 hours of daylight and it's often mostly overcast, and I'm running my heatpumps to warm the house. But if I have solar/battery capacity to make that work, I'm going to have way too much capacity for most of the year.
Solar + battery for grid backup makes more sense in places with shorter duration outages and were peak electricity use is in the summer rather than the winter.
Good point on grid reliability. It’s almost like our grid is too reliable because although we probably have an outage once or twice a year it’s so short duration that we don’t even lose perishables in the fridge or freezer <knocks on wood>. But certainly a great reason to do it if you’re blacked out for days multiple times per year.
With the way prices are dropping for solar and batteries I would recommend doing the calculation again 3-5 years from now as with the current cost trajectory specially if it is just 20-30% more expensive. I think even prices for electric appliances will drop as more people start to use electric appliances like heat pumps etc as they will also enjoy economies of scale and labour cost drop as more installers get used to working with them.
It’s a good call. One thing I struggle with, especially given recent times, is that the trades seem like they’ll only be getting more expensive so even though the material costs may drop the tradespeople will eat up that savings. It’s great for those professionals, of course, but as of late you would’ve been better off doing any project “yesterday” that requires a tradesperson rather than waiting until “tomorrow” (perhaps with the exception of when lumber prices were insane a couple of years back).
> If there are others I’d love to understand them.
In the past year or two we’ve had an eight day power outage, five day power outage, multiple 1-2 day power outages, and who knows how many hour-ish interruptions and gasoline or propane for the generator get expensive and inconvenient running it for long periods of time.
Our main limit to how long we can comfortably survive without power is that we’re on well and septic. Without power the pumps for both aren’t running so we have no running water and no sewer. We have bottled water on hand to at least cover drinking, but if we were to just shit in a hole outside we would basically just be dumping raw sewage into our water.
Local power generation and storage is very interesting to me.
Your comment nicely demonstrates the pitfalls of looking at everything through a financial lens. The point of backup power isn't as a financial investment, but rather providing your personal convenience/comfort/protection. So yes, buying a generator is spending money.
Financially, most likely he could have an even higher "ROI" with a much smaller solar battery (sized for the daily use of time shifting), plus a generator for long term outages. Unless your grid rates are such that you can buy electricity off peak, charge the battery, and then profitably sell it back to the grid (effectively operating your own small time distributed grid storage), sizing a battery to provide for multiple day outages is cost prohibitive.
The point of adding solar is you don't need a battery sized for multiple day outages, just enough to get you through the night. And instead of a generator which you need to spend money to maintain every year and otherwise just depreciates, you get solar panels which make you money every day.
If you have net metering, then buying a sizeable battery bank is in the same category as buying a generator - a depreciating asset mostly going unused.
If you don't have net metering, then you get bitten by needing to massively oversize your solar array to still fill the batteries on the worst case dim winter days, so that you can make it through the next night (likely powering necessary heating loads). That overproduction is then wasted on peak days unless you can find something clever to do with the excess electricity.
I'm sure there are other scenarios with time-varying electricity rates, but I'd think that calculation would be much closer to general time shifting with the backup power as an added benefit, rather than revolving around the backup power.
I think it would be interesting to consider partial or hybrid solutions, which may vary by climate zone. I.e. a solar battery setup that can cover typical day/night cycles with a tuned amount of excess, with some "survival" mode where you conserve battery charge for longer outages.
You'd need some pre-planning to segregate different circuits to do partial transfers and/or some smart appliances which can operate in reduced power modes. In the survival mode, maintain a critical baseload of lighting and food storage, perhaps even with some freeze-proofing heating mode that does not hit regular comfort targets. Use high-load equipment only when there is excess solar input beyond what is needed for battery maintenance etc.
You could also provide the right kind of exterior input to allow a portable generator to be added to the system in an emergency situation. This could support higher peak loads or recharge batteries when solar input is insufficient.
No heating loads, it's a natural gas furnace. Loads are just lights, furnace blower, and other ancillary loads.
It's not exactly the same as just adding battery backup, because the marginal cost of adding battery backup to a solar inverter is far lower than getting an inverter for just backup purposes, and solar allows a smaller battery.
It seems like there are two justifications for solar if you’re on the grid. Either you want to do right by the environment (totally good, though very pricey, reason to do it!) or your electricity costs are very high. If there are others I’d love to understand them. Maybe if you’re a prepper (not making fun) then that’s another reason.