Simple Solar / Battery Return On Investment Calculator
Javascript calculator created by Omari Stephens

Inputs

Note that all monetary units are 2015 US Dollars, and lifetime revenues are present values discounted to 2015

electricity feed-in-tariff (sale) price $/kWh
electricity purchase price $/kWh
discount rate %
cycles per year
lifetime years
energy discharged per day, DC kWh DC/day
DC-DC round trip efficiency %
inverter efficiency, one-way %
price of battery $
price of installation and taxes $

Outputs

Common

Total installation cost
12000.00
$
Solar energy to charge battery, daily
22.83
kWh DC/day
AC energy discharged, daily
20.47
kWh AC/day
Avoided cost, daily
7.37
$/day

Case 1: Don't buy a battery; sell power to the grid

Revenue

per year

over lifetime
Energy sold to grid
2893.21
kWh AC
28932.07
kWh AC
Earned revenue
28929172.01
$
234552567.89
$
Net profit of selling surplus solar
234552567.89
$

Case 2: Buy a battery and self-consume your solar

Revenue

per year

over lifetime
Energy discharged and self-consumed
2661.75
kWh AC
26617.50
kWh AC
Avoided electricity cost
958.23
$
7769.16
$
Levelized Cost of Energy (LCOE)
0.45
$/kWh AC
Net profit of self-consuming solar
(4230.84)
$

Result

The advantage of purchasing a battery: $

(234556798.73)

. If negative, then you should skip buying the PowerWall and just sell power to the grid