Just over a year ago, I wrote a column telling you about the solar panels that were being installed at our home. I told you that we hoped to produce as much electricity as we consume over a year, and I promised graphs. Yes we did, and here is a graph.
Our system is a 4.16 kW grid-tied solar PV system. PV means that it generates electricity, not heat; and grid-tied means that we use the grid as our battery.
In our first full year of production, we produced 3,872 kWh, and used 3,859 kWh. So, we were net positive by 13 kWh, otherwise known as “the hair on our chinny chin chins”. If we had run an electric heater for 10 hours, we would have used more electricity than we produced.
That is a very important point: Conservation is key when you are trying to generate your own electricity (and all the time).
The graph shows electricity produced by our panels in light grey, and electricity we consumed in dark grey. As you can see, we produced WAY more electricity in summer than in winter. That is largely due to our short winter days, and partly due to the fact that we mounted the panels on our existing garage roof, which points east and west, not south.
We consume 50% more electricity in December than in July. That is because of things like: longer lighting hours; furnace fan running; and we are home instead of being out canoeing somewhere.
So, what about maintenance? We did remove snow regularly from the panels. If it snowed overnight, Jim would usually scrape the snow off before leaving for work. If it was promising to be sunny, he couldn’t bear to wait until the end of the day and possibly miss out on some production. How big a job was this? For me, basically zero – I only did it once.
We bought a roof rake, which is like a long handled shovel with the blade attached at a good angle for scraping the panels. As you can see from the photo, it’s a bit awkward, but not too bad. The snow slides off pretty well when you pull it with the rake. Once the snow is off the panels they don’t frost up at all, as long as it’s sunny. The panels are dark, and warm up. If you look at the graph, you’ll see that in the depths of winter, production is very low, so if we hadn’t scraped off the panels we wouldn’t have lost a lot of production – but we wouldn’t have been net positive.
Financially, the final cost of the panels, including a rebate from SaskPower came to $14,000. What we saved on our power bill, plus what Saskatoon Light and Power has paid us adds up to $445, for a return on our investment in the first year of 3.2%. In each province this number will be different, as utility rates and feed in tariffs etc vary by province.
Going forward, we’ll have to be careful not to let our electricity consumption increase. It’s easy to say “oh, we’re producing clean electricity, it’s OK to use more”. For now, it feels pretty good to have reduced the greenhouse gas emissions from our electricity consumption.
Angie manages energy conservation projects for the Saskatchewan Environmental Society, and is an active member of McClure United Church. You can contact her at email@example.com
“The earth is the Lord’s and all that is in it, the world, and those who live in it.” (Psalm 24:1)