I’ve been so excited to share this information! I love graphs and data and I’d be lying if I said that the solar panel data wasn’t one of the things we were most excited about when our panels were installed. Below I’ll share some of the ways that we monitor our system.
This is a great resource to understand how solar panels work, so if you have a moment, check it out!
In order to understand what we’re measuring there are defintions for the terms used to measure output:
- Watt (W): The watt is a method of measuring the rate of energy transfer of an appliance. A one watt lightbulb, for example, will change one joule of electrical energy into light energy (and some heat/sound) every second. It is a measure of an appliance’s power*
- Kilowatt (kW): 1000 watts is called a kilowatt, written as kW. It is also known as (103) watts*
- Kilowatt-hour (kWh): The unit used by many electrical utility companies is the watt-hour (Wh); which is the amount of energy used by [a] one-watt load drawing power for one hour. The kilowatt-hour (kWh), which is 1,000 times larger than a watt-hour, is a useful size for measuring the energy use of households and small businesses. A typical household uses several hundred kilowatt-hours per month**
Examples of some of our monitoring data:
- Figure A: This graph shows an almost perfect solar generation day
- Figure B: And a bad solar generation day! You can see where the sun came out when the power generation increases.
- Figure C: This is a representation of our solar panel array and the power ( in watts) that each panel was generating at 3pm today!
- Figure D: This is recent data from our electrical utility provider. The bars above zero mean we consumed power that day and the bars below zero mean that we earned credit.
A couple questions that we’re often asked:
How much will solar panels cost?
This is driven by many different factors though ours was about $2.30 for each watt that the system is able to generate.
How much energy will the system produce? Is it the same in summer and winter?
Our system is 7.4 kW (7400 watts) made up of 20 panels that can produce between 450 and 1200 kWh per month, depending on the intensity and duration of sunlight we receive. For example, a full day of sunlight in December may generate 10 to 15 kWh because the days are shorter and the angle of the sun is lower than in the summer such that there is less light directly shining onto the panels. On a sunny day this month (June) we are generating approximately 45 to 50 kWh per day.
To put this into context, our average daily energy use is 25 to 30 kWh so we’re currently selling about 20 kWh back to our electric utility company on a sunny day. This 20 kWh is then registered as a credit to us with our electric utility provider. We can then use the credits in the fall and winter when our panels are not generating as much energy.
We still pay for a portion of our power usage most months. Our strategy with solar panels was based on our utility provider’s program of stepped rates. If we exceed a certain threshold of usage then we begin to be charged more per kWh. The goal of our panels was to keep us out of this higher rate usage for the year rather than generating enough for all of our power needs.
How much will it save?
This is a difficult question as we are not generating free power at this time. We estimate that, at current rates, the panels will have generated enough power to pay themselves off in 15 to 17 years. This calculation is influenced by our energy provider’s rates, how much power we generate, and interest rates if you consider time value of money. The panels should last for about 30 years in our climate therefore we should be generating free power for many years after our payback period ends. Until the panels have paid for themselves we think of it as fixing the price of a portion of our power bill which reduces our exposure to price increases.
Was the installation complex?
In our city and province we were required to have the solar panels installed by a licensed installer who had obtained proper permits. As we are tying into the power grid there are a lot of risks if the installation is not done correctly, therefore this is not a do-it-yourself project.
We were told that our solar panels could be installed on our roof in one of two ways: a hole in the roof made to bolt the panel racking to the structure, or ballast (heavy weights) would be used to hold the racking down. We opted to bolt the panels to our roof and our provider offered a warranty for their work.
Are there any government programs or rebates available for solar panel installation?
There are no rebates or tax incentives available in our jurisdiction at this time for the installation of solar panels; however, depending on where you live you may have access to government programs that encourage creation of clean energy.