Further thinking about what you'll actually get, it looks like a decent average price per kWh of installed home battery backup is about $1,000/kWh. So if we got $10k of batteries installed, you're looking at 10kWh of energy you can store.
Let's say you're in California, which has a pretty decent swing in energy prices available to the home consumer. You'll see prices swing between $0.27 to $0.65/kWh. You've got a 10kWh battery pack, so you can arbitrage something like $0.38/kWh * 10 kWh = $3.8/day, assuming you get a full charge cycle and ignoring efficiency for simplicity's sake. $114/mo. So assuming you didn't have any loans and you're ignoring opportunity costs on that $10k, your break-even is in ~88 months or ~7.3 years.
After a decade of ~$114/mo, you'll have offset $13,680, assuming you always used a full charge and you experienced no other maintenance costs and bought it cash on hand and that energy prices didn't change and had a perfectly efficient inverter to charge and discharge the batteries and the batteries still had 100% charge capacity the whole time. The 10-year CD, which you could just forget about for a decade, stands at $17,310.
And this is for one of the few markets in the US that really offers that big of a time of use plan other than "free nights and weekends***" (with pages and pages of fine print and other fees) For instance, I just looked at a time of use plan available to me here in North Texas. 9AM-4PM I'm billed at $0.068 for the generation, $0.050029/kWh plus a flat $4.23/mo for delivery. Outside of that window I only pay the delivery cost. But that means I'm only really able to arbitrage $0.68/day with a 10kWh setup. That's 490 months or a hair over forty years to break even.
Let's say you're in California, which has a pretty decent swing in energy prices available to the home consumer. You'll see prices swing between $0.27 to $0.65/kWh. You've got a 10kWh battery pack, so you can arbitrage something like $0.38/kWh * 10 kWh = $3.8/day, assuming you get a full charge cycle and ignoring efficiency for simplicity's sake. $114/mo. So assuming you didn't have any loans and you're ignoring opportunity costs on that $10k, your break-even is in ~88 months or ~7.3 years.
After a decade of ~$114/mo, you'll have offset $13,680, assuming you always used a full charge and you experienced no other maintenance costs and bought it cash on hand and that energy prices didn't change and had a perfectly efficient inverter to charge and discharge the batteries and the batteries still had 100% charge capacity the whole time. The 10-year CD, which you could just forget about for a decade, stands at $17,310.
And this is for one of the few markets in the US that really offers that big of a time of use plan other than "free nights and weekends***" (with pages and pages of fine print and other fees) For instance, I just looked at a time of use plan available to me here in North Texas. 9AM-4PM I'm billed at $0.068 for the generation, $0.050029/kWh plus a flat $4.23/mo for delivery. Outside of that window I only pay the delivery cost. But that means I'm only really able to arbitrage $0.68/day with a 10kWh setup. That's 490 months or a hair over forty years to break even.