Do a Home Energy Audit Before You Electrify

There's a sequencing rule in electrification that saves more money than any equipment choice: fix the envelope before you size the equipment.

The logic is direct. A heat pump is sized to your home's heating and cooling load. Reduce that load and you buy a smaller unit — one that costs less, draws less electricity, and may keep your total electrical load under a threshold that would otherwise force a service upgrade.

Do it in the other order and you've bought and installed equipment sized for a house that no longer exists.

What an audit should produce

An audit before electrifying is not optional detail — it produces the load calculation that sizes the heat pump. Sizing equipment to a leaky, under-insulated version of the house means buying capacity you would not need after basic envelope work, and paying to run it for twenty years.

How much does a leaky envelope cost?

Your heating load is the rate at which heat escapes. It comes from:

• Air leakage — conditioned air escaping and outside air entering through gaps
• Conduction — heat moving through under-insulated ceilings, walls and floors
• Duct losses — conditioned air lost from leaky ducts, especially in attics or crawlspaces
• Windows and doors — both leakage and conduction

Every one of these is fixable, and fixing them is generally cheaper per unit of load removed than buying equipment to serve that load.

The compounding effect on electrification

This matters more for electrification than it did for gas, for two reasons.

Heat pumps are sized more tightly. An oversized heat pump short-cycles, dehumidifies poorly in cooling mode, and runs less efficiently. Right-sizing depends on knowing the real load. See oversized HVAC problems and heat pump sizing.

Load reduction is electrical capacity. A smaller heat pump means a smaller circuit and a smaller contribution to your load calculation. In a house that's close to the capacity limit, envelope work can be the difference between needing a service upgrade and not. That makes insulation an electrical strategy, not just an energy one. See electrical capacity for an all-electric home.

It also reduces the need for resistance backup heat in cold climates, which is the single largest peak load in many all-electric homes. See all-electric heating in cold climates.

Can you do your own energy audit?

Free, an hour, and it finds the obvious problems.

Feel for drafts on a windy or cold day — around windows, doors, outlets on exterior walls, attic hatches, where pipes and wires penetrate walls, and at the rim joist in the basement.

Look at attic insulation. Is it even? Does it cover the whole area? Is it compressed? Can you see the tops of joists across large areas?

Check the attic hatch. Very commonly uninsulated and unsealed, and it's a large opening at the top of the house.

Inspect ducts in unconditioned spaces — attics, crawlspaces, garages. Look for disconnected sections, gaps at joints, and missing insulation.

Look for daylight around door frames and at the garage-to-house door.

Check bath and kitchen fans vent outside rather than into the attic.

Score your baseline with the home energy score calculator.

What does a professional energy audit include?

Two things you can't do yourself:

Blower door test. A calibrated fan depressurizes the house and measures total air leakage. This turns "it feels drafty" into a number, and — used with a smoke pencil or thermal camera — locates exactly where the leaks are. It also gives a before/after measurement so you know the work did something.

Thermal imaging. An infrared camera shows missing insulation, thermal bridging and leakage paths inside walls you can't open.

Many audits also include combustion safety testing on existing gas appliances — checking for backdrafting and CO. That's worth having regardless, and it's especially relevant if you're partially electrifying, since removing one appliance can disrupt shared venting. See orphaned water heater venting.

Many utilities offer subsidized or free audits — check your utility's programs. Start with utility rates.

Which envelope improvements pay back fastest?

1. Air sealing. Usually the best return per dollar. Sealing the attic plane, the rim joist, and penetrations around plumbing, wiring and ducts.

2. Attic insulation. Heat rises; the attic is where it leaves. Relatively inexpensive and often the largest single conduction improvement.

3. Duct sealing and insulation. If ducts run through unconditioned space, losses can be substantial — and it's conditioned air you already paid for. See ductwork problems and cost.

4. Basement and crawlspace treatment. Rim joist sealing and insulation; crawlspace encapsulation where appropriate.

5. Wall insulation. More invasive and more expensive, but significant in older homes with empty cavities.

6. Windows and doors. Often the first thing homeowners think of and usually the worst value per dollar for load reduction — though weatherstripping and caulking around existing windows is cheap and worthwhile.

One caution: don't over-tighten without ventilation

A tighter house exchanges less air with outside, which is the point — but it also means indoor pollutants and moisture accumulate more.

If you're doing substantial air sealing, plan for mechanical ventilation. This matters more if any combustion appliances remain, since a tight house can affect their draft. A professional audit should flag this, and a good contractor will raise it unprompted.

See home humidity control and indoor air quality after electrification.

Then size the equipment

With the envelope improved, size the heat pump to the new load — via a proper load calculation from your contractor, not a rule of thumb or a match to the old furnace's capacity.

The old furnace's size is particularly misleading: gas furnaces are frequently oversized, so matching it perpetuates the error into equipment where oversizing costs more. See heat pump sizing BTU and what size air conditioner do I need.

When to skip ahead

If your furnace has already failed, don't sit in a cold house to insulate first. Instead:

• Have the load calculation done anticipating the envelope improvements you commit to making
• Do the envelope work soon after
• Accept that you may be slightly oversized in the interim

That's a reasonable compromise. What isn't reasonable is sizing to the leaky house and then never doing the envelope work.

The bottom line

Envelope work before equipment, because every unit of load you remove is equipment you don't buy, electrical capacity you don't need, and running cost you don't pay. Do the free walkthrough first, then a professional audit with a blower door before any major heating purchase. Air sealing and attic insulation are the best value; windows usually aren't. And if you tighten the house substantially, plan the ventilation.

Baseline with the home energy score calculator, size equipment with the heat pump sizing calculator, or read the home electrification roadmap.