Can someone critique my back of the napkin ROI on adding a Battery to my Solar system.
I have a 15Kw Enphase system (new)
I live in NH with Eversource at $0.24 / KWh
200 Amp service.
Eversource offers 75% NetMetering (I think, I get mixed info on how it’s calculated). No off peak rates.
Most batteries are around 92% efficient (round trip).
You can think of NetMetering (for me) as 75% efficient (round trip).
Roughly 1 battery for $10K with a capacity 10Kwh.
NetMetering is unlimited Batteries for $0K with unlimited capacity and for unlimited storage time and 0 loss.
The battery is 17% more efficient than NetMetering. With a cap of 10Kwh a day.
So let’s guesstimate that 6 month of the year I over produce.
That’s 10Kwh * 30 days a month * 6 months
1800 KWh. But we are only saving 17% so I’d save 306 kWh (by storing in the battery vs the grid). That’s being optimistic.
Now multiply that by electric utility rate. 306 * 0.24 kWh = $73/yr savings.
$10,000 / $72 = 136 years to break even
I use about 30 KWh a day. Probably could cut that back to 10 kWh during a power failure. House is all electric (geo thermal heat). So 1 day of backup. It would cost a fair bit more to allow for true off the grid mode during power failure and I have a manually switched generator.
I have a 15Kw Enphase system (new)
I live in NH with Eversource at $0.24 / KWh
200 Amp service.
Eversource offers 75% NetMetering (I think, I get mixed info on how it’s calculated). No off peak rates.
Most batteries are around 92% efficient (round trip).
You can think of NetMetering (for me) as 75% efficient (round trip).
Roughly 1 battery for $10K with a capacity 10Kwh.
NetMetering is unlimited Batteries for $0K with unlimited capacity and for unlimited storage time and 0 loss.
The battery is 17% more efficient than NetMetering. With a cap of 10Kwh a day.
So let’s guesstimate that 6 month of the year I over produce.
That’s 10Kwh * 30 days a month * 6 months
1800 KWh. But we are only saving 17% so I’d save 306 kWh (by storing in the battery vs the grid). That’s being optimistic.
Now multiply that by electric utility rate. 306 * 0.24 kWh = $73/yr savings.
$10,000 / $72 = 136 years to break even
I use about 30 KWh a day. Probably could cut that back to 10 kWh during a power failure. House is all electric (geo thermal heat). So 1 day of backup. It would cost a fair bit more to allow for true off the grid mode during power failure and I have a manually switched generator.