East+West roof may now be "better" than southern exposure ?

[ImInPhxAZ]

E/W let's you cram more daily kwh production into a smaller inverter too, keeping it running near peak longer. Less of a curve and more of a wide plateau. It's a valid strategy when the needs call for it.

[bcroe]

I have a house with an east/west facing roof. PVWatts predicted 20% less production due to facing east (versus south). I had an 8.4kw array installed on the east roof, and it is working decently, considering the orientation (18.1 mW-hrs over 36 months in Minnesota, or 6 mW-hrs/year).

I started driving an electric car, so my power use went up by about 3 mW-hrs last year (but my gasoline bill went down $100/month). Now I'm looking at the west roof of my house, and realizing that I could install a second array, and it would pay for itself. Despite the penalty for not facing south, I could produce 60% more power than if I had a north-south facing roof.

Obviously, the payoff for east/west is slower than south-facing, but if it means that you can produce 60% more, then having an east-west roof could be an asset, and not a liability. It depends on your needs and priorities. (for example, in my case, east/west facing payoff is still faster than a solar garden membership).

I don't know the configuration, AC and DC ratings of your system. But with a string system, a string or 2
on the west side could be tied directly in parallel (with fuses) to the existing inverter. That, because the 2
sides will peak at different times, and avoid clipping by the inverter. How many can be added in parallel
depends on peak separation, controlled by the angle towards E and W (probably limited by the roof).
Bruce Roe

[J.P.M.]

Too bad the sun doesn't shine at night when you can charge an EV from solar at your home.

Yea, but the Almighty compensated for that by giving some of humanity a fairly reliable and infinite storage facility called the grid.

[SunEagle]

Be careful. If you have super off peak rates available (say from 0000 hrs. until 0500 hrs. for example) and you charge an EV between those times, and at what may be very low rates, adding PV for the purpose of offsetting what might be a very low cost to fuel an EV may not be cost effective.

As an example only, @ $0.05/kWh for an examp[le super off peak rate, and at 3 miles/kWh for EV mileage and 12,000 miles/yr., ~ $200/yr. "fuel cost". Back of envelope: 6,000 kWh/yr./8 kW array ~ 750 kWh/yr./STC kW --->>> 4,000/750 = 5.33 STC kW array will be needed for saving $200/yr. At, say, $3.00*.7/installed STC W ~ $11,200 for a 5.33 STC kW array that will offset $200 in EV "fuel cost"/yr. 11,200/200 ~17.9 yrs. using the moron payback method.

Moral of the story: Check what you'll be paying to charge the EV.

Too bad the sun doesn't shine at night when you can charge an EV from solar at your home.

[J.P.M.]

Be careful. If you have super off peak rates available (say from 0000 hrs. until 0500 hrs. for example) and you charge an EV between those times, and at what may be very low rates, adding PV for the purpose of offsetting what might be a very low cost to fuel an EV may not be cost effective.

As an example only, @ $0.05/kWh for an examp[le super off peak rate, and at 3 miles/kWh for EV mileage and 12,000 miles/yr., ~ $200/yr. "fuel cost". Back of envelope: 6,000 kWh/yr./8 kW array ~ 750 kWh/yr./STC kW --->>> 4,000/750 = 5.33 STC kW array will be needed for saving $200/yr. At, say, $3.00*.7/installed STC W ~ $11,200 for a 5.33 STC kW array that will offset $200 in EV "fuel cost"/yr. 11,200/200 ~17.9 yrs. using the moron payback method.

Moral of the story: Check what you'll be paying to charge the EV.

[SunEagle]

An East / West array will always be much better then any array with North facing panels (if you live above the Equator).

The % difference between which way the panels face is dependent on not only the Sun's path but also the type of weather you get in the morning or afternoon.

Clouds and Fog will reduce the % production even if they face South.

[specialgreen]

I have a house with an east/west facing roof. PVWatts predicted 20% less production due to facing east (versus south). I had an 8.4kw array installed on the east roof, and it is working decently, considering the orientation (18.1 mW-hrs over 36 months in Minnesota, or 6 mW-hrs/year). When I had the array installed, I was wishing I'd bought a house with a south-facing roof.

I started driving an electric car, so my power use went up by about 3 mW-hrs last year (but my gasoline bill went down $100/month). Now I'm looking at the west roof of my house, and realizing that I could install a second array, and it would pay for itself. Despite the penalty for not facing south, I could produce 60% more power than if I had a north-south facing roof.

Obviously, the payoff for east/west is slower than south-facing, but if it means that you can produce 60% more, then having an east-west roof could be an asset, and not a liability. It depends on your needs and priorities. (for example, in my case, east/west facing payoff is still faster than a solar garden membership).