Solar Photovoltaic (PV) Panels

Solar Panels on Roof

This entire project began with the announcement of the renewal energy program that the province of Ontario had plan to implement in April of 2009, and the feed-in tariff that was to be offered.  In looking at what the best method to take advantage of the program was from a small scale perspective, we quickly realized that it would be cash flow positive from the solar panel investment, and that it would help pay for some (if not all) of the additional energy efficiency upgrades for the house.  This became the lynch pin in this entire project from an energy perspective as well as from a financial perspective.

We began by looking at lots that were on streets with an east-west direction fronting on the south side of the street that were as wide as possible within our budget, while still fitting our personal requirements for area amenities.  We were fortunate enough that, within a very short period of time, we were able to locate and secure the purchase of a 100′ wide lot in a suburban area of Toronto.  Our next step was to design the house to maximize the roof space available for the solar panels, and in doing so we included four design aspects for this purpose:

  • The first was to specify that the roof pitch for the south facing portion of the roof to be an 8/12 rise (33.7° pitch), which was within a couple of degrees of optimal for our geographic location.
  • The second was to set back the 2nd floor rear wall so that the south facing roof could extend from the top of the first floor all the way to the ridge (see architectural drawings).
  • The third was to use two gable ends instead of a hip roof to maximize the south facing roof.
  • The fourth was to incorporate a tandem garage; this allowed us to add roof space and storage space without increasing the conditioned area of the house.

By incorporating the above design aspects, we were able to design a roof with over 2,300 sqft of area to mount the solar panels, which allows us to mount a 30kW PV system, very likely to be the largest roof mounted residential system in the province.  In comparison, most approved systems for residential mounting in this region has been in the 6kW-8kW range, with many being as small as 2kW-3kW.

We chose to work with Honeybee Solar based on their knowledge, and their willingness to look at source different solutions, and in our case, panels and inverters that will allow us for the greatest payback.  The panels are from CEEG and from Eclipsall, about 15% panel efficiency, while the inverters will be from Aim Energy (local Ontario content) through Honeybee Solar, which provides some of the highest yielding inverters on the market.  In their test site in Southern Ontario, they were able to generate over the course of a year 70% more power on a flat-straight-to-the-sky panel installation than a typical DC installation.  In real world use, we are expecting about 1.3kWh/W of panel, a 25-30% than a traditional string inverter installation.

Our system of about 30kW will cost somewhere in the neighbourhood of $200,000, but the 20 year contract that the Ontario Power Authority offers for a system of this size will pay back $0.713/kWh, and we anticipate we will generate more than $30,000/year.  In a pre-tax calculation, on an annualized basis, this would offset close to a $450,000 mortgage based on a 20 year amortization and a 2.99% interest rate (as of July 2012).

Total production is anticipated to be around 40,000kW/h per year, of which we anticipate about half will be used by the house for daily electrical uses as well as for cooling, and the other half will be used for heating in the winter using a combination of our Daikin Altherma heat pump as well as natural gas.  Our calculation includes the BTU used by burning the natural gas, converted to kWh.

Our near real-time generation statistics can be viewed at http://www.tigoenergy.com/site.php?31_Thornheights.

CaGBC LEED for Homes – Points can be acheived in Energy and Atmosphere, in the renewable energy section (EA 10.1), or exceptional energy performance (EA 1.2) via the ERS/HERS method.

2 Replies to “Solar Photovoltaic (PV) Panels”

  1. I am a bit confused by some of the information on your PV system.
    1. You must mean that you anticipate generating 50,000 kWh per year, not 50,000 kW.
    2. When you say Ontario Power will pay $0.713/kW, this would amount to only $21.39 for an installed 30 kW system. On the other hand, if you meant to say they will pay $0.713/kWh generated, then that number sounds very high. I pay about $0.10/kWh (in U.S. dollars) from Xcel Energy in Colorado, and they pay me only about $0.03/kWh for energy generated in excess of what I use.

    Thanks,
    Lee Dodge

  2. Lee,

    Thanks for correcting me. Yes, both should read kWh; we are being paid at a rate of $0.713/kWh contracted for 20 years. And yes, that’s a lot more than the $0.09-$0.13/kWh that we pay to buy electricity from the local utility. On one hand, the government is encouraging green energy and putting incentives on the generating side, but the downside is that our electricity rates are likely to go up as more people take advantage of the relatively rich subsidies. The government has chosen a production approach of subsidizing output instead of subsidizing on the installation side on a per W of panel basis, and it is this incentive that has made this project possible. We bear the full cost of the equipment up front, and in our case we’ve chosen the most efficient inverters that we can find in order to maximize the production.

    Part of the feed in tariff requirements has to do with local provincial content, so part of the scheme is to be able to generate employment opportunities in the province relating to the green energy sector. And the reality is that we’ve never paid in full the cost of electricity, and only now are we paying for the past generation’s cost through debt retirement charges and such added onto the electricity rates, as well as the subsidies paid through the tax dollar as the real cost of electricity is much higher than what the province has been charging for the past many years. The capital costs are now factored into the FIT rates, whereas in a typical electrical generation project, the capital costs has always been approved and paid for through tax dollars. The rate is also based on size of system; less than 10kW systems are paid $0.802/kWh, and can be as low as $0.443 for large scale ground mounted systems.

    Granted, my contracted rate of $0.713/kWh is still rich, and even more so with the high efficiency inverters I have…

Leave a Reply