It was a big dumb cloud

Don't worry I'm not going to upload a graph like this every day. But I could, I mean it's my blog and all, but I won't. The mystery of that huge dip in the first day's graph has been solved. it was likely just a big dumb cloud. Today's graph is much more uniform and at a better 5 minute resolution.

I'm really happy with the data logger (an SMA webbox).

My First Solar Production Graph

Our system is still in testing mode, but now we've hooked up the webbox data logger and so I can get data out of it. I had knocked up a script to hit it every minute and get data but it crashed halfway through the day. Luckily the built in webserver and ftp server had all the data I needed for today's production and here's a graph.

That dip is interesting, I'll be interested to see if it's there in tomorrow's data too. It could be a tree shading the panels at that time of day, who knows. Looking at the data, the voltage of the panels is constant. I'll be looking into this more.

We made over 28kWh in one day!

Solar panels installed!

Well it only took two days to install the solar system. Everything turned out great and we're really happy with it.

The system got turned on for the first time today which was also the day the building inspector would sign off on our permit. While it was on for testing we generated 10kWh of power which is worth about $2 or $4 depending on which tier of power you are offsetting.

We're allowed to offset the power we use at night or on cloudy days but not sell back more than we end up using. There are no batteries, the electrical grid is effectively our battery. If there is a power outage, our inverter notices and refuses to output any power (to stop us electrocuting people working on restoring power).

Now we just need to wait for the utility company to come out and give us a fancy smart meter (for time of usage billing) and to bless the system and we'll be allowed to leave it on all the time.

From 20110607solarinstalled

The coolest thing was seeing our electric meter running backwards while the system was running!

Solar Power System Ordered

We've ordered Solar Power Panels to be installed at the new house. We've always wanted solar power, but at the old house most of our south facing roof was taken up with the panels that heat the pool water by pumping pool water through them. There is a little roof space over the smaller bedroom, but nothing big enough to put a solar power system on.

Our new house is a different story. I thought the main part of the roof was all south facing, but if you look in Google maps on the satellite imagery the long part of the roof is south east facing and the smaller roof over the bedroom and office is south west facing. Where we are south west is best because it's less likely to be foggy in the afternoon so that's where the panels are going.

I talked to 3 companies to get their bids on the job and we chose the one we liked that had a good deal and seems to know (and explain) their stuff the best.

Here's the specs of the system we ordered:


Total System Size: 4.320 kW DC Power (STC) / 3.746 kW AC Power (CEC)
Estimated Annual Production: 6,530 kWh 
PV Panel Description: 24 x Schuco USA LP Model: MPE 180 MS 05 
Inverters: Qty. 1 - SMA America Model: SB4000US (240V)

Initially it was only going to be 22 panels, but since the inverter is a fixed cost I asked if we could max it out with panels to reduce our cost/kW even though that meant a slightly slower return on investment since the extra electricity we would be replacing would have been cheaper than the solar. I also got a webbox which will allow me to upload and archive my data easily.

Getting at my data and not depending on an external service was a key factor in our choice of system. I had looked at microinverters from Enphase. Microinverters are an inverter for 2 panels so there would be a lot of inverters up on the roof. This makes adding extra capacity (for a plug in car?) at a later date much easier. But this thread in the forums taught me that my data would be held captive by Enphase and I'd have to pay $1/panel/year forever to upload and view my data which little protection if they end up going out of business.

This week we should see the permits issued and the equipment ordered and hopefully install will happen later next week and then it'll get turned on when PG&E takes their sweet time in turning it on. The credits and tax rebates make it an attractive offer that will hopefully pay for itself in 6-7 years they say. I'll be happy if it pays for itself in under 10, it should work for at least 25 with the only maintenance being panel cleaning and replacing the inverter after 12 or so years.

We did look into leasing the system, but it just didn't offer the return on investment we wanted and seemed as if we were mostly just giving our roof and sun over to someone else to make all the upside on it. It'd be a good option if we couldn't afford the system, but luckily we can.

After looking at this I've also been considering putting a solar pool pump at the old house. But since it's so expensive I'll likely only seriously look into it once our current pump dies.