Boiler Sizing Guide
The #1 cause of boiler inefficiency, short-cycling, and premature failure in Greater Vancouver is incorrect sizing. Bigger is not better — a properly sized boiler runs longer, modulates lower, and lasts decades longer than an oversized one.
Quick sizing reference for BC homes
Approximate guidance only — every job requires a real heat-loss calculation.
| Home Profile | Approx. Heat Loss | Combi Boiler Suggestions | Heating-Only + Tank Suggestions |
|---|---|---|---|
| Vancouver West Side, ~1,500 sqft heritage | ~45,000 BTU/hr | NCB-150E, SL 20-160, ECO Tec 110 | NHB-80, V-10, ECO 110 |
| East Van bungalow, ~2,000 sqft | ~55,000 BTU/hr | NCB-180E, SL 20-160, Alta 120 | NHB-80/110, V-15, ECO 110 |
| Burnaby split-level, ~2,500 sqft | ~70,000 BTU/hr | NCB-210E, SL 28-175, Alta 150 | NHB-110, V-15, Aspen 110 |
| Surrey/Langley new 2-storey, ~3,500 sqft | ~85,000 BTU/hr | NCB-240E, NCB-240H, M160CN, SL 33-225 | NHB-150, V-20, Aspen 150 |
| West Van executive, ~5,000+ sqft | 120,000+ BTU/hr | NCB-300H, Q205SN | NFB-200H/250H, Aspen 250, Vitodens 200-W |
| Strata building per unit | Project-based | Cascade — IBC HC, Viessmann Vitocrossal 300, Brute Elite | Commercial cascade |
Why sizing correctly matters
30%
Gas savings potential
A right-sized condensing boiler can save 20-30% versus an oversized non-condensing unit.
2x
Service life
A right-sized boiler can last 20+ years; an oversized one short-cycles and may fail in 10.
$2,000
Rebates
FortisBC and CleanBC rebates require properly-sized, certified-installed equipment.
Common sizing mistakes
We re-size for accuracy, not for guessing.
Sizing by square footage alone
Ignores insulation level, window quality, ceiling height, climate exposure. A poorly insulated 2,000 sqft home and a well-insulated one can have very different heat loads.
Replacing "size for size"
The old boiler was likely oversized — most pre-2010 installs were 50-100% larger than needed. Replacing same-size perpetuates inefficiency.
Oversizing for DHW only
Combi units must size for the larger of heat load OR DHW flow demand — but the heat load typically determines the modulation range needed.
Ignoring modulation ratio
A 200,000 BTU boiler with 5:1 turndown can only modulate down to 40,000 BTU — too high for many spring/fall days, causing short-cycling.
Forgetting altitude
Higher-altitude installs (above 2,000 ft elevation) need derated gas pressure. Affects North Shore, Burke Mountain, Heritage Mountain homes.
What we factor into a heat-loss calculation
Our free in-home assessment uses CSA F280 methodology.
Get a real heat-loss calculation — free
Don't guess. We come to your home, measure properly, and recommend the right brand and model for your specific situation. No obligation.
Right-sized boiler. Lower bills. Longer life.
Call GasBoilers.ca — A CanroHeat Division — for expert installation, repair, replacement, maintenance, and emergency service.