After years of research, watching the industry and pricing, and keeping a close eye on financial incentives and subsidies, I finally decided it was time to install a solar photovoltaic array on my house roof. I already use the sun to heat my pool water for free - why not harness some free electricity for my family as well and cut our bills down quite a bit?
Typically known as solar PV, this means the type of solar panels that produce electricity to offset usage in the home to bring down my power bills. My home is fairly large based on square footage, and has numerous add-ons that add to my power draw such as a pool pump that runs 8 hours per day in summer, a secondary pump which runs the cleaner, three HVAC systems (one for each floor including basement), two refrigerators, a preschooler who requires a lot of laundry, and a shop/garage where I often work that has it's own small mini-split HVAC system to heat and cool. My wife and I both work full time jobs from home, so we also use two computers and 4 monitors plus associated devices (radio, speakers, fans, lights, A/C during the day, etc). I do as much as possible to keep the house "tight" and reduce usage where possible. A few years back when I first became interested, I interviewed several companies and picked one that was clearly the most experienced and knowledgeable. They were eventually the company I chose to do the installation which is happening now.
Some things I've done
before considering this solar PV array to reduce energy usage or save the energy I'm already using include:
- Renewed and upgraded my attic insulation to a solid R-39 rating
- Sealed off all penetrations from 2nd floor ceiling into attic including adding foam around all can lights, checking for penetration and sealing up everything we found
- Adding an insulated box around the attic pull-down stair
- Re-insulating all knee-walls (partial walls) in attic that may have to do with heat transfer between conditioned space and unconditioned space
- Had a whole house energy analysis done to check for air leakage, HVAC duct leakage, and much more
- Changed all high or medium use bulbs to either CFL, CCFL, or LED
- Tinted the windows to increase heat rejection
- Set thermostats at 76-78 at most times to reduce HVAC usage
- Set outside lights on timers to avoid wasted energy
- Unplugged appliances or devices that are not frequently used that draw "phantom" power
- STILL TO DO: Take my "kill a watt" meter around the house and find any last devices drawing power that shouldn't be and unplug them
Here's my past 12 months of energy usage so you can get an idea:
Note that last summer we had my daughter at home and in the basement a lot so the HVAC got used a lot more than it does now (I have it programmed to stay OFF at night now) and that it was low on freon, increasing usage unknowingly.
So what's involved? We're installing 27 Bosch 245W (DC) solar panels on my roof, in two sections (one facing rear, one facing side). The ridgeline between them is actually the ideal direction to face, but they are at good enough angles that they'll produce great output. There is an inverter on the side of my house that converts the DC power from the panels into AC power I can use. What happens is that it actually spins my meter backward when it makes power and only charges me for anything I use above what I produce.
In the summer I'll be covering roughly 25-40% of my actual usage with the panels and in spring/fall/winter, closer to 50-60%. Here's a chart similar to above, but I've added estimated monthly production in total kWh and the % of my usage that this covers (note: this is just kWh production versus usage, not cost - since my cost structure goes way down, and since my main usage is during the day when production is highest, even if I'm only producing say 30% of what I need overall, this still means my bill could be 50% less than what it used to be):
Here are the nitty gritty details about my system including payback numbers and "time to break status quo":
Summary showing estimated yearly production and other details:
More details about the system:
Time to break status quo. Status quo (red line) is what I have now (same as every other house) - just keep paying for electricity when you use it. The green line (with solar PV array installed) shows that, after the initial hit of the $31k spent, you quickly get back the tax credits and Progress check, so you start at -$13k or so in the hole, but make that up quickly not just with other tax credits but with offset power savings AND by being on a new rate schedule for the power you do use, which now costs less than before. I'll explain below.
Cash payback chart. Conservatively around 9 years, but faster if I use less power and manage my peak power usage wisely (will explain below).
There's a big outlay up front to get started and get the system up and running, but you can see that I'll get a big $5300 check from Progress right away, then when I do my taxes in March or April, another $13k or so in tax credits, so that at least helps cut a lot of the cost down very quickly. My power bills will also go down immediately which will add up quickly. You can see that after Progress, Federal, and NC incentives, my actual cost for the entire system on a cash basis (not including time value of money) is only about $8600. The system should last 30 years or more. We'll be living in the house at least another 20 years, so it's a wise investment. Energy rates go up by a few % every year and some years by more so when you figure this in, it makes even more sense.
The numbers shown are tax
credits not tax
deductions meaning you take your end of year total tax due and take those numbers right off the bottom line, not before figuring your tax. It's a big difference.
One more thing you need to know is the new Progress rate schedule I'll be on once I'm on net metering, meaning use minus production equals my billed amount.
Right now, we're all on a straight residential rate schedule. Current rates as of today (Aug 24, 2012) are 10.73 c/kWh of usage all day, every day.
When the new system is installed, I'll be on a NEW system with peak and off peak rates. Peak rates are charged at 6.377 c/kWh of usage and are as follows:
April 1 - Sept 30: 10am - 9pm
Oct 1 - March 30: 6am-1pm, then 4pm-9pm
Several holidays are also excluded from this such as New Years Day, Good Friday, Memorial Day, Independence Day, Labor Day, Thanksgiving Day and day after, and Christmas day. When any of these fall on a Sunday, the Monday after will be considered "off peak."
All other hours are off peak and are charged at 5.003 c/kWh of usage.
On top of this, there's a peak demand charge of $5.02 per kW for all on peak usage. This means they take the maximum number of kW you use during any 15 minute period during the month and multiply that by $5.02 and add that as a surcharge to your bill. So if you have a lot of high demand devices (say, multiple HVAC, clothes dryer, oven, etc) coming on all at the same time, this could easily drive your peak demand surcharge through the roof and diminish an otherwise reasonable bill. Therefore I will be installing simple control circuitry on my main two HVAC systems to prevent them from turning on their compressors at the same time with the upstairs given priority. Each HVAC compressor can easily use 2-3kW by itself, so just keeping them from coming on at the same time can save me $10-15 per month on my bill with no other changes.
Here are some photos of what's been done so far. The inverter and conduit has been installed and the brackets to hold the rails are about 90% done. Tuesday they'll finish up the last 2 rails, after moving the 2 vent pipes you can see in the photos, and lay all the panels in place. From there it has to be inspected by the city and then Progress has to come out and swap out the meter for the new one that can spin backward (in effect - nothing is really spinning as it's digital). Then we can turn it on and check how well it's making power.
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