Monday, June 24, 2013

Solar, part 1

Medford is doing a community push for solar, which convinced me to take another look at solar for our property. The city’s chosen installer is SunBug, and I’ve gotten a proposal from them.

Choosing an installer is tricky. There aren’t a lot, and most haven’t been in business very long. But since they are going to be messing with your roof and your electrical system, you want someone good. There aren’t a lot of reviews. You can see an Excel file of all the companies who have done projects in Massachusetts in the past few years that qualified for a state rebate program. Brightstar Solar gets great reviews, but isn’t doing installations in Medford. Sungevity was very hard to talk to in 2012, and Next Step Living has frighteningly bad reviews, so I’m skipping those two. I’ve been waiting to hear back from Blue Selenium, and Sunlight Solar is coming next week to do a site evaluation.

Direction matters. South would be optimal. On the map, it looks like our unshaded roof faces ESE. SunBug thinks it’s close enough to SE that we’ll be ok.

Pitch matters. Our roof is 45 degrees, which is a decent compromise between wanting steeper in the winter and less steep in the summer.

With both direction and pitch, I’d expect to find decent curves showing the dropoffs in production and calculators that let you see the results. I haven’t found those yet. But solar companies must be using those.

Shading matters. A little shading can have a huge detrimental effect on production since solar panels are wired in series (both within the panel and in a string of panels). The only shading we really have to worry about would be if the tree in the park next door gets much taller, but the problem is that we don’t have the right to trim that tree if it does. Perhaps the city would like to agree to trim that tree if it starts to shade our solar panels?

Roof condition matters. SunBug told us we have to redo our roof before we can install solar. I expect other solar companies will tell us the same thing. We have no leaks, so this is sooner than we would replace the roof otherwise, but roofs don’t last forever.

The electrical panel matters. SunBug told us we need to install a subpanel or redo our main panel in the basement to install solar. My idea of putting a subpanel in the attic to make this easier is apparently not a great idea because the attic gets very hot in the summer, which isn’t great for the wiring.

The choice of panel matters. We can produce a lot more power if we use SunPower 327-watt panels than if we use typical 250-watt panels. The downside is a bit more up-front cost.

Financial assumptions make a huge difference. What will happen to the cost of electricity over the next 10 years? What’s the opportunity cost of the investment? Is SREC income taxable? (At the moment there’s a good argument that SREC income is not taxable, since it’s less than the cost of putting in the panels. But it makes a big difference if it becomes taxable, since that’s the bulk of the payback over the first 10 years.) How does depreciation on the system work with my home office? Will my insurance cover the solar panels? Will the system increase or decrease the house’s value? (Looks like a modest increase in the short term, but my guess is that it won’t matter in the long term.)

Financing matters. About 2/3 of new systems are leased rather than owned. Since we may want to sell in 5-10 years, and leasing makes that harder, we need to own the system.

The roof geometry of the front of our house is terrible for curb appeal. Will a monolithic solar array on the top section make that better or worse? How will a different roof color affect the appearance, since we can choose a different color when we reshingle?

But I like the idea of having more of our electricity come from solar, and this is the step we can take towards that. It’s not an ideal site, and there aren’t ideal conditions here, but it still may pay off in about 7 years (based on some reasonable assumptions). That’s pretty good.

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