- August 25, 2022
- Posted by: AliensFaith
- Category: OBJECTIVE PRESS
|
The property is in Massachusetts. The roof plane of the house is south-facing with an azimuth of 193 deg and tilt of 31 deg. The other panels are on a detached two-car garage with a gambrel-style roof. The data for those roof planes are azimuth 283/103/103 and tilt 22/22/55 respectively. The company who provided this proposal will install panels on the roof plane with 55 deg tilt. It is very close to the ground so there isn’t much risk of physical harm to the installers. This company does employ its own installation crew. The 55 deg roof plane has 95% annual solar access with only the months of Dec and Jan having solar access of less than 90%. TSRF is 63%. The proposal uses two 5000W SolarEdge HD Wave inverters. I’ve also run the proposal with a single 10000W inverter. The two-inverter solution is an extra $1400. I ran hourly production data in pvwatts for the system. Based on pvwatts production estimates I’ll see next to no clipping with the 10,000W inverter and about 5,000 kWh of annual clipping with the two 5,000W inverters. I’m assuming it would be one inverter per structure. From my pvwatts calculations, I can estimate that with a house inverter of 5,000W I’ll see the previously mentioned 5,000 kWh of clipping annually. The garage inverter won’t clip at all. However, the estimates from the solar company show 5,000 kWh (AC) annual production from the two-inverter solution. I assume this effect is due to the 10,000W inverter not being driven hard enough consistently to run at its best efficiency. I’ve wrung out as much efficiency out of the home as I can. It’s an older house (built in the 1930s) but all windows have been replaced with efficient double-hung windows, the walls have been insulted, and I’m working with a local efficiency org to upgrade the insulation in my attic. I’ve put a lot of smart automation to curtail electricity consumption. I’m a few weeks away from installing mini-split heat pumps in the house. The current heating system is gas fired hot water baseboard with indirect domestic hot water off the gas boiler. I’m hoping to use the heat pumps to shed some natural gas usage when outdoor temps are such that the heat pumps can run at decent efficiency. Once the mini-splits are in, I can pretty reliably estimate my annual electricity consumption at 10,500 kWh. With plans to add an EV in the next few years, I estimate that 12,000 miles/year of driving with a reasonably efficient EV should require around 3,400 kWh of electricity to charge at home. This would drive my annual consumption total to right around 14,000 kWh (AC). Since the chosen panels, REC Alpha Pure 405W, should still be generating 92% of their year 1 production in 25 years, I’d need to start with about 15,200 kWh (AC) in order to still be producing 14,000 kWh (AC) in 25 years. Please feel free to second guess any and all assumptions and your thoughts on the proposal. Thanks submitted by /u/rclarkston |
