Measuring solar power
Power is measured in watts. A kilowatt (kW) is 1,000 watts of power. A megawatt (MW) is 1 million watts of power. Watts measure the rate of power at a moment in time.
Kilowatt-hours (kWh) measure the amount of energy used over a specific time period, in kilowatts per hour. Electricity used for powering home electronics and small or large appliances, whether for just a few seconds or for most of the day, is measured in kilowatt-hours.
Total electricity consumption for a home appears as kilowatt-hours on a monthly utility bill, for example, 600 kWh. A homeowner is responsible to pay for this usage at their current electricity rate, usually shown as cents/kWh.
Likewise, micro-generation from a home solar power system appears on a monthly utility bill as kilowatt-hours. When it occurs, micro-generation shows as a credit on a utility bill as cents/kWh.
Sizing home solar power systems
The exact number of modules or panels required for a home solar power system depends on a household’s annual energy consumption, the amount of sunlight a home receives, available roof space, and the size or power of each solar module (in watts), among other considerations.
Solar power systems are sold as a measure of the capacity of energy they can generate in kilowatts, for example, a 5-kW system. This means that all the solar modules or panels together add up to 5 kW. This could look like a system of 20 solar modules, each with 250-watts of power: 250 W x 20 modules = 5,000 W or 5 kW.
The size of the solar power system needed depends on how many kWh of electricity a home uses in a year and by how much a homeowner is looking to offset their usage from the grid. The greater the energy requirements, the larger the solar power system needed to offset this usage.
In Alberta, the
Micro-generation Regulation stipulates that customers can generate enough power to meet some or all of their annual electricity consumption, but not more. When a customer generates more power than they need at any given moment, they’ll receive a credit on their bill from their retailer—at their electricity rate—for every (kWh) sent back to the grid.