How Much Solar Power Do You Need?

The second question customers often ask us at Suncatcher Solar is “How many solar panels will I need?”.  The first question is usually “What will solar power cost?” but we need to answer the second question before we can answer the first.

Solar panels come in many sizes.  They can be used alone or combined to make up a solar array. To figure out the size of array you would need for your home you will need to know how much electricity you use and how much sunshine is available where you live.  Saskatchewan has excellent conditions for solar energy.

How Much Electricity Do You Use?

electrical meterIf you already have electricity from an electrical utility, this will be an easy question to answer.  Take a look at your utility bill and find the current and previous meter readings.  The difference between these readings is the amount of power that you have used between the two dates of the readings.  The amount of power will be a number of kWh.  Looking at the dates for which this reading applies, you can calculate what your monthly or annual electrical usage is.  Most homes use in the range of 600 – 1200 kWh per month.

If you don’t have electricity yet and are planning to use a solar power system instead of connecting to an electrical utility, you will need to estimate what you are going to use by doing a load analysis.

Now that you know what you need for electricity, it’s time to see how much power a solar panel can produce and how many of them you will need.

How Much Electricity Does a Solar Panel Produce?

Solar panels derive their power from sunlight.  The brighter the sunlight the more power the panel produces – up to its rated capacity, which is given in Watts.  When you buy a solar panel you will see that the panel size is given as, for example, 10 Watts or 100 Watts or 240 Watts.  Combining ten 100 Watt panels into one system will give you a 1000 Watt – or a 1 kiloWatt (kW) solar array.

If you have full sun shining on the array for one hour (1 Sun Hour), the array will have produced one kiloWatt-hour (kWh) of electrical energy.  This is the same unit as the electrical utility charges you for on your electrical bill.

Solar Array

The average number of sun hours per day for your area can be found on a global solar insolation map or you can focus more closely on a map of your own area.

World Map of Sun hours


What Size of Solar Array Do You Need?

Multiply the daily energy in kWh from the map by 30 days/month – this will give you the sun hours available.  Then divide the kWh per month that you are being billed by the electrical utility by the monthly sun hours available. This will give you the size of the solar array (in kW) that would generate enough electricity to meet your monthly bills.

The actual size of solar array you decide to invest in will depend on a few other factors as well:

  1. Space for solar panelshow much space you have for panels a large array can require considerable space and may need to be ground mounted if there is not enough suitable roof space available.  For a roof mounted system measure the dimensions of clear south facing roof space (length of the roof and height to the peak or to obstructions such as a row of vents.
  2. whether you are doing a stand alone system or a grid-tied system– an off-grid, or stand alone system, will have to be large enough to supply all your needs, even in the winter, but a grid-tied system can be smaller since the electrical utility will supply any shortfall.
  3. whether your local electrical utility offers net metering or feed-in tariffs – net metering is a program that credits you for extra power you produce against future bills from the utility.  The best size of system is one that will provide most of your electricity so that you effectively offset your electricity bill.  Feed-in tariffs actually pay you for the electricity you produce, usually at a premium rate, so for this type of program it may be worthwhile to invest in a larger system and use the production as a source of income.
  4. your budget – sometimes it’s not possible to purchase the optimum size due to budget constraints, but you can always start with a smaller system and add on later as you can afford it.  In the meantime, the system you have installed will be saving you money.
Call us toll-free at 1-877-441-2355 or send an email with your electrical usage and space you have available for solar panels and we will give you a free estimate.

Solar Power Mounting Options

Solar panels take space – 400 to 1200 square feet or more, depending on how much solar electricity you want to generate. If you want to get top solar production in Saskatchewan, the panels should face due south and at an angle to best capture the sunlight.  But what, exactly, is that angle?  The sun moves across the sky during the day, constantly changing position.  It is also much higher in the sky during the summer than it is during the winter.

1.  Solar Trackers

Solar Trackers

Solar Trackers

A system that tracks the sun would be an ideal solution.  However, a tracking system needs a massive mount to accommodate all the panels and a complex control system to make the tracking automatic.  This makes the system expensive and the moving parts will require maintenance.

Solar panels have come down in cost so much that it is far cheaper to buy more solar panels and put them on a mount that is fixed at an angle that provides a good compromise.  Typically, for the 30% extra power production that you can get from a tracker, you could easily buy 50% more solar panels if you have the room for them.

Solar trackers do make economic sense if you are short of space or if there is a reason to squeeze maximum production out of a fixed size of solar power system.  This is the case, for example, in Ontario, Canada where the feed-in tariff pays a premium rate for systems up to 10 kW.

2. Roof Mounts

Solar Power on House Roof

A roof clear of obstructions is best for mounting solar panels

The least expensive way to mount your system is directly on your roof.  The mounting system fastens to the roof trusses and provides rails on which to mount the panels.  The rails keep the panels a bit above the roof itself to provide ventilation for the panels.  Solar panels are more efficient at lower temperatures, so ventilation is important.

A simple roof mount is the way to go if you have enough south facing roof space at an angle approximately equal to your latitude.  If this is a grid-tied system a lower angle can also work well since you usually produce a lot more power in the summer when the sun is higher in the sky.  With grid-tied systems you can usually feed that extra power back for credits in the winter or sell it back to the utility.

Ballasted Solar Mount for a flat roof

Ballasted Solar Mount for a flat roof

If your roof is flat, or just doesn’t have  a steep enough slope, the roof mount angle can be adjusted to compensate for that.  This adds some expense, but can significantly improve the production.  Ballasted roof mounts, that don’t require any roof penetrations, are also available for flat commercial roofs where the possibility of leaks is a big concern.

Keep in mind that you also want your solar array to be free of any shading.  Watch for dormers or trees or a roof on a more southerly part of the house that might shade your panels.

3. Ground Mounts

Ground mounted Solar Array

Ground mounted Solar Array

Perhaps you have no suitable roof space but lots of room on the ground.  This is often the case on acreages and farms.  A ground mounted array is the second most economical choice.

A rack for the panels is set up at a suitable angle and mounted high enough above the ground to account for snow cover.   The racks require more material than a sloped roof mount, so this adds some expense, as does the screw pile foundations.

Ground mounted arrays have their advantages.  You can more easily choose a good location with minimal shading.  The array is also easily accessible for cleaning and clearing off any snow cover that accumulates on the panels.

4. Pole Mounts

Solar Panels on a Pole Mount

Solar Panels on a Pole Mount

Another alternative for smaller solar power systems is one or more pole mounts.   These are like a tracking mount but without the expense and complexity of the tracking system.  Pole mounts are more expensive than ground mounts but can be manually adjusted for seasonal angles.   It is also easier to select a good location for a pole mounted array.

The limitation with a pole mount is that you don’t want to mount too many panels on one pole.  The array of panels is like a sail in the wind, so the larger the number of panels you mount on a pole, the more massive the pole and foundation will need to be.  The other alternative is simply to use more pole mounts but each mount will need a pole and concrete foundation, with its attendant costs.

Contact Us for help in choosing the best solar mounting system for your home.