Runtime evidence · sourced load
A furnace blower draws 233 W while running. 11 stations clear the capacity, inverter, and startup checks at that load.
By the BatteryRank Engineering Team
01 · Runtime ladder
Nominal capacity × depth of discharge × inverter efficiency ÷ sourced average draw.
| Capacity class | Estimated runtime | Evidence |
|---|---|---|
| 300 Whstep 1 | 1 hr | Furnace blower (1,000 CFM ECM) load · 2026-07-20 |
| 500 Whstep 2 | 1.6 hr | Furnace blower (1,000 CFM ECM) load · 2026-07-20 |
| 1,000 Whstep 3 | 3.3 hr | Furnace blower (1,000 CFM ECM) load · 2026-07-20 |
| 2,000 Whstep 4 | 6.6 hr | Furnace blower (1,000 CFM ECM) load · 2026-07-20 |
These are comparison projections, not a promise. Temperature, inverter behavior, cycling, and the individual station's measured delivered capacity can change real runtime.
02 · Reading the numbers
A gas furnace burns gas for heat and uses electricity only to move air, which is why a modest battery can keep a house warm through an outage that would defeat any attempt to heat electrically. The blower modelled here is an ECM — an electronically commutated motor that ramps up smoothly and holds about 233 W per 1,000 cfm of airflow.
Assuming every furnace has an ECM blower. Older PSC blower motors draw substantially more and start abruptly, and they are still extremely common. Check the furnace label before planning around this figure. The second mistake is the same one as with well pumps: a furnace is hardwired, so a transfer switch or interlock is part of the project.
The 233 W figure comes from a DOE test of a compliant ECM unit at 1,000 cfm. Your furnace moves whatever air its blower is set for, and its label lists the actual amperage. Igniter and control-board draw are separate and brief.
03 · Passing stations
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Critical-load fit
Why it fits
6,967 W above the plan's running load (7,200 W continuous output)
Main compromise
4,800 W below the highest output reserve across 11 eligible models
Best all-round fit
Why it fits
75.6 BatteryRank score — the highest of any station that fits this plan
Main compromise
4 points below the highest-scoring eligible model across 11 eligible models
Maximum useful reserve
Why it fits
89.7 projected runtime hours
Main compromise
2,560 Wh below the largest sourced expanded reserve across 11 eligible models
This ordered data view is separate from the three recommended buying strategies above.
Runtime uses each linked model's sourced capacity and output data; open its dossier for provenance.
Solar effect
Computed with this model's sourced solar-input limit and BatteryRank's published harvest assumptions. Check the solar method → · Model sources →
04 · Evidence record