There is an old line in the energy world: the cheapest kilowatt-hour is the one you never use. It is true, and it is why many people save more by fixing the house first and adding solar second. This guide walks through what to do and in what order, as of late 2026.
Why the order matters
Solar is priced by size. At the time of writing, installed cost for a grid-tied system runs roughly $2.50 to $3.80 per watt before incentives (CAD), so every extra kilowatt you do not need saves a few thousand dollars. If a house wastes a lot of energy, you need a bigger system to cover it. Trim the waste first, and the system you buy can be smaller, so you pay less and still end up with the same comfort.
What an audit looks at
A professional energy audit walks through the house and measures where heat escapes and where equipment wastes power. Typical steps include:
- A blower door test, where a fan pulls air out of the house to reveal drafts
- Thermal imaging, where a camera shows cold spots in walls and ceilings
- An insulation check of the attic, walls, basement and rim joists
- A look at heating and cooling equipment: age, type and condition
- A check of windows and doors for seals, glazing and gaps
- A review of appliances and lighting and what draws the most power
You get a report, often with a list ranked by cost and benefit. Some provincial programmes still ask for an audit before paying a rebate, so confirm the current rules with Natural Resources Canada or your utility.
Things you can do yourself this weekend
Not everything requires a specialist. These are cheap and effective: seal gaps around windows, doors and plumbing with caulk or weatherstripping, add door sweeps, swap the last old bulbs for LEDs, set the water heater thermostat to a sensible temperature and insulate exposed hot water pipes. A programmable thermostat, clean furnace filters and switching off devices that sit in standby all day also help.
Bigger projects, in a typical order of payoff
| Step | Why it comes here |
|---|---|
| Air sealing | Costs little and helps comfort a lot |
| Attic insulation | Often the best value per dollar |
| Basement and wall insulation | Worthwhile, more disruptive |
| Windows and doors | Expensive, so do them when they wear out |
| Heating upgrades, including heat pumps | Biggest change to the electricity bill |
A worked example
Imagine a 1970s two-storey house that uses 14,000 kWh a year, much of it electric heating. After air sealing and attic insulation, the owner trims winter use and lands at 12,000 kWh. Using the rule of thumb that a kilowatt of solar in southern Canada often yields roughly 1,100 to 1,400 kWh a year, the original target needs about 10 to 13 kW, and the new one about 8.5 to 11 kW. That is a couple of kilowatts less, which at the cost range above is a saving in the thousands of dollars. An audit may cost a few hundred dollars, so it often pays for itself on paper, and you keep the comfort gains.
Do not stop at the current number. If you plan an electric vehicle or a heat pump, your use will rise, and a good installer will help you plan for that. Our panel sizing guide shows the arithmetic, and heat pumps and solar together covers the electrification side.
Where solar fits in
Once the house is tighter and more efficient, look at your usage again. That new, lower number is what you size solar against. Then run it through a payback estimate: the solar payback guide shows how rates and system size change the answer, with payback often quoted around 8 to 15 years depending on province and rates.
Finding programmes and an auditor
Audits are sometimes subsidised, and some incentive programmes require one before you do any work. The federal grant and loan that once helped fund retrofits are no longer open to new applicants as far as we know, so look at provincial and utility offers, and use our incentives checklist to confirm what is current. Choose an auditor who is independent of any company that sells windows, insulation or solar, so their advice is not tied to a sale. Ask for their qualifications and a sample report.
What to expect on audit day
Plan for two to three hours at home. The auditor will want access to the attic, basement and mechanical room, and will ask for a recent year of electricity and heating bills. Close windows, and expect the house to be depressurised for the blower door test, which is noisy but harmless. Afterwards you should get a written report with the leakiest areas and a ranked list of fixes. Keep it: some provincial offers and any installer will ask to see it, and a second audit after the work confirms what you gained.
A quick mindset shift
Think in three steps: reduce, replace, generate. Reduce waste with sealing and insulation. Replace old equipment with efficient models. Then generate power from the sun for what remains. People who follow this order tend to have smaller bills and fewer regrets.
Ready for the generating part? Start with the roof checklist, and browse the solar basics hub for the next steps.
Quick answers
Should I do an energy audit before installing solar?
It is a smart first step. Cutting waste lets you buy a smaller, cheaper solar system for the same comfort.
What does a home energy audit include?
Typically a blower door test for drafts, thermal imaging, an insulation check and a review of heating equipment, windows and appliances.