My family has a secondary residence (though currently primary during COVID) and would love to put solar on it.
Objective is to be green and to have backup during outages, so grid tied & Powerwalls.
Located in Long Island, NY
Utility has net metering with power banking across months.
Roof is North facing & above the tree line (Google Project Sunroof says we have 850 sq ft of space up there, for reference)
House is oil heat/hot water, and fully electric appliances for the rest.. no cooking gas.
Cooling is via a central air system on 1 level, plus 2 mini splits.
Fall/Winter electric usage has been ~30kWh/day (10kWh/day is EV charging / 20kWh is the house).
Estimating..
Summer usage would be 50kWh/day for 2 peak months based on prior experience.
Unoccupied usage will be closer to 5-10kWh/day based on appliance non-use.
Estimate 100% occupied during summer, 25% occupied remainder of year.
So works out to-
91 summer days at 50kWh/day
205 non-summer unoccupied days at 10kWh/day
70 non-summer occupied days at 30kWh/day
=24kWh/day average year round
I was planning to err on the side of under-sizing to an 8kW + 2 Powerall system.. I would over-generate for 205 days, break even for 70 days and then deduct from my utility power bank for 91 days, and the Powerwall would get me through a day or two of utility outage year round.
Does my math seem off somewhere or are there factors I may be missing?
Objective is to be green and to have backup during outages, so grid tied & Powerwalls.
Located in Long Island, NY
Utility has net metering with power banking across months.
Roof is North facing & above the tree line (Google Project Sunroof says we have 850 sq ft of space up there, for reference)
House is oil heat/hot water, and fully electric appliances for the rest.. no cooking gas.
Cooling is via a central air system on 1 level, plus 2 mini splits.
Fall/Winter electric usage has been ~30kWh/day (10kWh/day is EV charging / 20kWh is the house).
Estimating..
Summer usage would be 50kWh/day for 2 peak months based on prior experience.
Unoccupied usage will be closer to 5-10kWh/day based on appliance non-use.
Estimate 100% occupied during summer, 25% occupied remainder of year.
So works out to-
91 summer days at 50kWh/day
205 non-summer unoccupied days at 10kWh/day
70 non-summer occupied days at 30kWh/day
=24kWh/day average year round
I was planning to err on the side of under-sizing to an 8kW + 2 Powerall system.. I would over-generate for 205 days, break even for 70 days and then deduct from my utility power bank for 91 days, and the Powerwall would get me through a day or two of utility outage year round.
Does my math seem off somewhere or are there factors I may be missing?