Solar First Look

How we calculate

Our reports are built to be auditable: every number comes from a calculation you can follow, using data with a named source. AI is used to read electricity bills and to flag changes on rebate pages, never to produce the financial numbers.

1. Your roof

We use Google’s Solar API (building insights), which models the sunlight reaching each part of your roof from aerial imagery and 3D surface data, including shading from trees and nearby buildings. It returns roof sections (area, pitch, direction), possible panel positions and the yearly DC energy each panel position would capture. We only accept high- or medium-resolution imagery, and check that the building found is the one at your address.

2. Production

  • Google’s Solar API estimates how much sunlight each panel position receives over a year, in DC kWh, using 3D roof and surroundings models. We convert to AC with Google’s 85% factor (inverter, wiring, soiling and other losses).
  • We subtract a further 3% (1–6% across scenarios) for snow on the panels in winter.
  • Panels lose about 0.5% of their output each year.
  • We analyse 25 years, a common panel warranty length. Panels often last longer, which would improve the result.
  • Future savings are discounted at 4% a year, roughly what a low-risk investment might earn instead.

The month-by-month pattern comes from PVGIS (European Commission Joint Research Centre), NSRDB satellite data, for the nearest of ten BC and Alberta cities. As an independent cross-check we compare Google’s estimate for your best panels with PVGIS and Natural Resources Canada figures; if Google’s is higher, our pessimistic case uses the reference figure.

3. Your electricity use

From your bill (read by AI, then checked by our code and shown to you) or figures you enter. Twelve months of data gives a high-confidence estimate; a single bill gives a low-confidence one, and we widen the range in the scenarios.

4. Bills with and without solar

For each of 25 years, we calculate your bills both ways using your utility’s full rate structure:

  • BC Hydro: Residential Conservation Rate (tiered) with Self-Generation Service (RS 2289). New solar customers since 1 July 2026 are on RS 2289: production above use in a billing period earns 10¢/kWh as a credit against Energy Charges only. BC Hydro does not say whether unused credit carries forward; we assume it does in the expected case and that it is lost in the pessimistic case.
  • FortisBC (electric): Residential rate with Net Metering. FortisBC banks surplus kWh and settles the balance once a year at its power-purchase rate, which it does not publish on its net metering page. We value any year-end surplus at zero, which is conservative; the suggested system is sized not to produce more than you use.
  • ENMAX Power (Calgary): Rate of Last Resort energy + ENMAX Power D100 delivery. Energy rate is the 2025–2026 Rate of Last Resort, which ends 31 December 2026; the 2027–2028 rate had not been published when this was checked. Most Albertans are on a retailer contract with a different rate: your bill’s rate is used when we can read it.
  • EPCOR Distribution (Edmonton): Rate of Last Resort energy + EPCOR residential delivery. Energy rate is the 2025–2026 Rate of Last Resort, which ends 31 December 2026; the 2027–2028 rate had not been published when this was checked. Most Albertans are on a retailer contract with a different rate: your bill’s rate is used when we can read it.
  • FortisAlberta: Rate of Last Resort energy + FortisAlberta Rate 11 delivery. Energy rate is the 2025–2026 Rate of Last Resort, which ends 31 December 2026; the 2027–2028 rate had not been published when this was checked. Most Albertans are on a retailer contract with a different rate: your bill’s rate is used when we can read it.
  • ATCO Electric: Rate of Last Resort energy + ATCO Electric D11 delivery. Energy rate is the 2025–2026 Rate of Last Resort, which ends 31 December 2026; the 2027–2028 rate had not been published when this was checked. Most Albertans are on a retailer contract with a different rate: your bill’s rate is used when we can read it.

Savings are the difference. Fixed charges are never counted as savings. In Alberta, we estimate how much solar you use directly (it avoids delivery charges) with an hour-by-hour model of an average day’s solar output against a typical household load shape, on bright, average and dull days. That shape is generic, so the share is a key uncertainty and varies across our scenarios.

5. Costs

  • Installed price per watt (DC), before incentives: our low / base / high range is built around published Canadian averages and widened because prices vary a lot between companies and roofs. It is not a quote.
  • Small systems cost more per watt because of fixed costs (permits, electrical work, connection); we use a minimum installed price of $8,000.
  • A string inverter typically lasts 10–15 years. We include one replacement in year 13 at $0.30 per watt. Microinverters often carry 25-year warranties, which would remove this cost.
  • An allowance of $75 a year (rising with inflation) covers monitoring, occasional inspection and minor repairs.
  • BC exempts solar panels, and inverters and wiring bought with them, from PST; most quotes already reflect this.

6. Incentives

We include an incentive only if it is open, we’ve verified its amount rule from the official source, and it applies to your utility or municipality. We always show results with and without it, because approval is never certain.

7. Choosing the system size

We evaluate every panel layout Google suggests for your roof and pick the one with the best value today (net present value, with potential incentives) that doesn’t produce more than you use in a year.

8. Scenarios and the verdict

Pessimistic: higher installed price, 10% less production (or the independent reference if lower), more snow loss, slower price rises, lower use and unused export credit lost. Optimistic: the reverse. The verdict follows fixed rules: worthwhile if it pays back within 15 years and still breaks even in the pessimistic case; borderline if it pays only in the expected case; unlikely if only the optimistic case pays; not worthwhile if none does; not suitable if the roof is too small or too shaded.

Limitations

We can’t see your roof’s condition, structure or electrical panel; imagery has a capture date; installed prices vary; rates and rules change. An installer must verify everything on site.