Well Pump Power Outage: Generator & Backup Power Guide Canada

Quick answer

A conventional private well normally loses active pumping when the pump loses electricity. Your pressure tank may keep the plumbing pressurized for a while, but it cannot refill itself while the pump is off.

There is also a Canadian water-safety wrinkle that a lot of outage advice misses. Health Canada says that pressure helps form a physical barrier against contamination. During a power outage, it advises private-well users not to open faucets, take showers, or flush toilets because consuming stored water depressurizes the system and increases contamination risk.

If your well system loses all pressure or no water comes from the faucets, Health Canada says to have the well water tested before using it. After power returns, flush the lines for a few minutes and make sure any treatment system is operating properly.

For backup power, do not choose a generator from pump horsepower alone. The safe sequence is:

1. identify the exact pump motor and any control box or VFD,
2. confirm voltage and phase,
3. find real running electrical data,
4. find manufacturer starting data, LRA, starting VA/W, or model-specific generator guidance,
5. verify that the backup source can supply the required voltage and motor-start demand,
6. then add the pump to the rest of your outage loads.

Ontario’s current outage guidance gives the practical destination: if you rely on a well-water system, use a backup generator to supply power to the pump. The hard part is sizing and connecting that backup without guessing.

What happens to a well when the power goes out?

A typical drilled-well system has several pieces that are easy to blur together:

• the groundwater well,
• a submersible pump down the well or an above-ground jet pump,
• a check valve and water line into the house,
• a pressure switch, control box, or variable-frequency drive,
• a pressure tank,
• optional water-treatment equipment,
• and the household plumbing fixtures.

When utility power fails, the electrical parts stop. A conventional pump cannot keep lifting water just because the well itself is full.

The pressure tank is different. It stores water under pressure using an air cushion, so it can continue pushing some water into the plumbing without electricity. But every litre drawn lowers system pressure because the dead pump cannot replenish the tank.

The ordinary outage sequence looks like this:

1. Grid power disappears. The pump motor, controls, VFD, booster, and any treatment equipment on dead circuits lose power.
2. Existing hydraulic pressure remains temporarily. The pressure tank may still hold a limited drawdown volume.
3. Using fixtures lowers pressure. Health Canada specifically warns against doing that during the outage because depressurization can increase contamination risk.
4. The pressure switch may call for the pump. Without electrical supply, nothing happens.
5. Pressure eventually falls too low for normal service. If the system loses all pressure or no water comes out, Health Canada says to test before using the well water again.
6. Power returns. The pump can repressurize the system if the equipment is healthy. Health Canada then advises flushing stagnant water for a few minutes and verifying that treatment is operating correctly.

This is an ordinary electrical-outage scenario. Flooding, wildfire damage, a submerged electrical component, a damaged wellhead, or a known contamination event changes the response. Do not energize damaged or wet equipment just because the utility comes back.

Your pressure tank is not a tank full of usable emergency water

A pressure tank’s advertised size is the vessel’s nominal capacity. It is not the amount of water you can draw between the pump’s cut-out and cut-in pressures.

That usable amount is called drawdown. It depends on the tank design, precharge, and pressure-switch settings.

A manufacturer example makes the point. Pentair’s discontinued Simer HT20 is a nominal 20 US gallon precharged tank. Pentair publishes these drawdown values for that exact model:

Source: Pentair Simer HT20 specifications. The model is discontinued and is shown here as an engineering example, not a product recommendation.

The same nominal tank can therefore have different drawdown depending on pressure settings, and a nominal 20-gallon tank does not provide 20 gallons of usable water between pump cycles.

Amtrol’s well-tank instructions likewise tell installers to set tank precharge relative to the pressure-switch cut-in, commonly 2 psi below cut-in for the covered tanks. That is another reason a generic “tank size × percentage” calculator is too sloppy for ReadyHome.

For a Canadian emergency-water baseline, see ReadyHome’s emergency food and water storage guide.

Find the electrical data before you buy anything

This is where well-pump advice usually goes off the rails.

A pump may be described as 1/2 hp, 3/4 hp, 1 hp, or 1.5 hp, but horsepower is a mechanical output rating. It does not tell you everything the generator or inverter sees electrically.

For the exact equipment, look for:

• manufacturer and model number,
• motor horsepower,
• voltage,
• phase,
• whether it is 2-wire or 3-wire,
• any external control-box model,
• any constant-pressure/VFD controller model,
• full-load amps (FLA),
• service-factor amps (SFA),
• locked-rotor amps (LRA) if published,
• real input watts if published,
• and manufacturer generator or alternate-power guidance.

Good places to find those details include the well-service paperwork, pump invoice, control-box label, VFD/controller label, pump manual, motor documentation, or a well contractor’s records.

Do not open energized control equipment just to read an internal label. If the useful information is behind a live electrical cover, stop and use the paperwork or a qualified tradesperson.

Why horsepower × 746 is not generator wattage

One mechanical horsepower is about 746 watts of mechanical output, but that conversion does not turn the horsepower sticker into the pump’s electrical input requirement.

An AC motor has efficiency, power factor, service factor, voltage, current, and starting characteristics. A control box or VFD can add another layer.

A current Franklin Electric example shows the distinction. Model 2445050117GS, a 1/2 hp, 230 V, single-phase, 2-wire submersible motor, publishes 5.0 A full-load current and 6.0 A service-factor current. The current product page does not publish a locked-rotor current or generator recommendation, so those values should not be invented from horsepower. See the Franklin 2445050117GS record.

Volts × amps is VA, not automatically watts

For a single-phase AC motor, volts multiplied by amps gives apparent power in volt-amperes (VA). Real power in watts also depends on power factor.

That means:

• 230 V × 5 A = 1,150 VA,
• but that is not permission to relabel the result as 1,150 W,
• and it says nothing by itself about locked-rotor or starting demand.

If the manufacturer publishes LRA, voltage × LRA can be useful as an approximate starting VA figure. Keep the unit as VA unless the manufacturer actually provides starting watts or enough information to establish real power.

Well Pump Backup Power Planner

Use this planner as a compatibility and data-quality gate, not as a magic horsepower converter.

It deliberately refuses to make a purchase recommendation when the inputs are not strong enough. That is the point.

What size generator do you need for a well pump?

There is no responsible universal answer such as “a 1 hp well pump needs a 7,500 W generator.” The exact motor and control architecture matter too much.

A defensible pump-only sizing process is:

1. Identify the exact motor and controller. Submersible motor, jet pump, 3-wire control box, VFD, or something else.
2. Confirm required voltage. A 230/240 V load needs a source capable of the correct 120/240 V output. A 120 V-only source is not fixed by having more watt-hours.
3. Confirm running requirement. Prefer published real input watts when available. If you only have volts and amps, keep the calculation in VA unless real power or power factor is known.
4. Confirm starting requirement. Use manufacturer LRA, starting VA/W, or current model-specific generator guidance. Do not assume 3×, 5×, or another folklore multiplier.
5. Check continuous and starting capacity separately. The backup source must pass both.
6. Apply any source derating. Fuel type, altitude, temperature, and manufacturer-specific conditions can reduce available generator output.
7. Add simultaneous household loads. Once the pump requirement is defensible, use the ReadyHome generator size calculator to combine it with the furnace, fridge, sump pump, lights, or other loads you actually intend to run.
8. Plan the connection separately. A hardwired well circuit cannot be made safe by generator capacity alone.

Ontario’s advice to use a backup generator for the pump is directionally simple. The equipment-specific sizing step is where homeowners need to slow down.

120 V vs 230/240 V is a hard compatibility gate

Do not start with generator wattage. Start with voltage.

A source that only provides 120 V cannot directly supply a pump or controller that requires 230/240 V. This remains true if the source has a huge battery, a large “surge watt” number, or pure sine-wave output.

North American equipment labels may say 115 V, 120 V, 230 V, or 240 V depending on the product and naming convention. Use the allowed input range on the exact pump or controller and the actual output configuration of the backup source.

Also avoid the reverse mistake: do not assume every private-well pump is 240 V. Current manufacturer product families include 115 V equipment, 230 V equipment, and dual-voltage jet pumps. The population-level claim “most well pumps are 240 V” is not needed to make a good backup plan.

2-wire vs 3-wire submersible pumps

Wire count can tell you something about control architecture, but it is not a generator-size multiplier.

Franklin’s current control-box documentation says its 3-wire, single-phase submersible motors use external control boxes, with Quick Disconnect (QD) and Capacitor Run Control (CRC) families. The QD and CRC boxes use capacitor starting, and CRC versions add a run capacitor. See Franklin Electric motor control boxes.

That is useful because it tells you to identify the external box as part of the system.

What it does not justify is a universal claim that every 2-wire pump needs a generator 50% larger than every 3-wire pump. Different motors and controls have different published electrical data. Use the exact model.

Jet pumps need the same electrical discipline

An above-ground jet pump may be easier to inspect, but it is still a motor load.

Pentair’s current Simer 4807S shallow-well jet pump is a useful example. It is a 3/4 hp dual-voltage pump, factory-set for 230 V with a 115 V conversion option. Pentair publishes full-load current of 7.4 A at 230 V and 14.8 A at 115 V. See the Pentair Simer 4807S specifications.

The example demonstrates two useful things:

• the same pump can have very different current at different supply voltages,
• and full-load current still does not establish the starting requirement by itself.

Jet pumps also have hydraulic concerns such as priming. Backup power does not fix a pump that has lost prime or has another water-side problem.

Constant-pressure and VFD systems

If your well uses a variable-frequency drive or constant-pressure controller, size the backup source from the controller input requirements, not the bare motor horsepower.

A current Franklin SubDrive20 Connect example accepts 230 V single-phase input, publishes 4,200 W maximum input power, and lists an input power factor of 0.95. It can drive several motor configurations on its output side. See the Franklin SubDrive20 Connect record.

The practical lesson is broader than that one model: the generator or inverter sees the drive/controller input. A soft or managed motor start does not mean the backup source can ignore controller voltage, input current, maximum input power, waveform, frequency, or manufacturer requirements.

Do not publish or rely on “VFD pumps have no startup concerns.” They have a different set of source-compatibility concerns.

Can a portable power station run a well pump?

Sometimes, but “enough watt-hours” is not the first question.

Check these gates in order:

1. Output voltage. If the pump/controller requires 230/240 V and the power station only provides 120 V, stop. It is incompatible for direct supply.
2. Continuous inverter output. It must carry the running load.
3. Motor-start capability. The source must handle the exact starting or controller requirement, not just advertise a vague surge number.
4. Connection method. A hardwired pump circuit needs an approved way to receive backup power. Do not improvise a panel or branch-circuit connection.
5. Energy capacity. Only after the first four gates pass does battery capacity in Wh or kWh tell you anything useful about runtime.

That ordering matters. A giant battery behind the wrong inverter voltage is still the wrong tool.

See Portable power station Canada for the broader battery-system selection framework.

Does pure sine wave solve well-pump compatibility?

No.

Pure sine-wave output can be relevant for some equipment, especially electronics and controls, but it cannot fix:

• the wrong voltage,
• inadequate continuous output,
• inadequate motor-start capability,
• a controller-specific requirement,
• or an unsafe connection method.

Likewise, there is no responsible universal “well pumps require THD below X%” rule. If the exact pump, drive, inverter, or generator documentation specifies a power-quality limit, follow that equipment-specific requirement.

Will rooftop solar run the well during a grid outage?

Do not assume it will.

BC Hydro says that during an outage, most self-generation systems automatically shut off to prevent power from flowing back into the grid. Approved battery systems and configurations can provide backup power, but ordinary grid-tied solar does not automatically keep household circuits alive.

Solar well pumping is also its own architecture. A purpose-built solar-direct pump, a solar pump filling a cistern, and an existing AC well pump backed by a home battery are three different systems.

That is why ReadyHome treats solar-powered well pumps as a separate future topic rather than pretending the same answer applies to every outage setup.

Your water-treatment equipment may need power too

Restoring the pump does not automatically restore every part of the water system.

Private-well homes can have electrically powered equipment such as:

• UV disinfection,
• iron or sulphur treatment,
• water softeners and control valves,
• booster pumps,
• pressure-boosting equipment,
• freeze-protection equipment,
• or other treatment and monitoring systems.

Health Canada specifically says that after power is restored, homeowners with treatment systems should make sure those systems are running properly and contact the manufacturer for any additional cleaning steps that apply.

If safe water depends on treatment, include those electrical loads and restart requirements in the outage plan.

Emergency water is still part of the backup-power plan

Even a well with a generator should have independent emergency water.

Reasons include:

• the generator may fail or run out of fuel,
• the pump may have a mechanical problem,
• the pressure system may lose integrity,
• treatment equipment may not restart properly,
• a wildfire or flood can create a water-quality problem unrelated to electricity,
• and a winter storm can make well service or fuel delivery difficult.

Health Canada’s emergency guidance uses a minimum 72-hour planning horizon and recommends at least 2 L of drinking water per person per day, with more for food preparation and hygiene.

Use Emergency food and water storage to plan water that does not depend on the well staying pressurized.

What to do after the power comes back

For an ordinary private-well outage, Health Canada’s current guidance is the baseline:

• if the system lost all pressure or no water came from the faucets, have the well water tested before using it,
• after restoration, run the water for a few minutes to flush stagnant water from the lines,
• make sure any treatment system is operating correctly,
• and follow manufacturer cleaning or restart instructions where applicable.

If the outage involved flooding, wildfire damage, electrical damage, or a known contamination event, use the emergency guidance for that event rather than treating it as a normal blackout recovery.

Winter outages can become plumbing emergencies

A long winter outage can take out both the pump and the equipment keeping vulnerable plumbing warm.

Health Canada recommends protecting vulnerable well-system piping by insulating/heating it, burying it below local frost depth, or locating it in a heated space such as a pump house. If a prolonged outage puts household plumbing at risk, see How to prevent frozen pipes for the broader freeze plan.

Do not assume generator power to the pump alone keeps every exposed line, treatment cabinet, pump house, or heat trace safe.

Connecting a generator to a hardwired well pump

A well pump is commonly a fixed circuit, so connection is its own project.

Canada’s current outage guidance says a backup generator may only be connected to a home’s electrical system through an approved transfer panel and switch installed by a qualified electrician. It also says never to plug a generator into a wall outlet to energize household wiring.

For a portable fuel-burning generator, the same federal guidance says to plan for at least 6 m (20 ft) from homes or buildings, direct exhaust away from openings, and keep carbon-monoxide alarms working.

Use Generator transfer switch Canada for transfer equipment, inlets, interlocks, and electrician questions. Use Generator safety Canada for placement, CO, fuel, and cord safety.

What not to do

• Do not intentionally use the pressure tank to empty during the outage. Health Canada advises against depressurizing the private-well system.
• Do not turn horsepower into generator watts with HP × 746. That is mechanical output, not a complete AC source requirement.
• Do not assume starting watts are always 3× or 5× running watts. Use model-specific data.
• Do not assume a 2-wire pump universally needs 50% more generator than a 3-wire pump. Exact motor/control data wins.
• Do not buy a 120 V-only source for a 230/240 V pump and expect more wattage to fix it. Voltage is a hard gate.
• Do not assume pure sine wave guarantees compatibility. Voltage, start capability, controller requirements, and connection still matter.
• Do not assume ordinary grid-tied solar runs during an outage. Most self-generation systems shut down unless configured and approved for backup operation.
• Do not backfeed household wiring. Use approved transfer equipment and qualified electrical work.

Frequently asked questions

Will my well work during a power outage?

Normally, the electric pump stops. The pressure tank may preserve some hydraulic pressure temporarily, but Health Canada advises private-well users not to consume stored pressure during an outage because depressurization increases contamination risk.

How long will water last in the pressure tank during an outage?

There is no responsible time answer from tank size alone. Drawdown depends on the exact tank, precharge, and pressure-switch settings, and household flow rate would determine time. More importantly, Health Canada advises against draining away system pressure during the outage. Keep separate emergency water.

What size generator do I need for a well pump?

Use the exact pump or controller voltage, running data, and manufacturer starting requirement or generator guidance. Then add other simultaneous loads in the generator size calculator. Horsepower alone is not enough.

Can a 2,000 W, 3,500 W, or 5,000 W generator run my well pump?

Maybe, but the headline wattage does not answer the question. Check required voltage, continuous capacity, and the exact motor-start or controller requirement. A 120 V-only generator cannot directly supply a 230/240 V well circuit regardless of its watt number.

Are well pumps 120 V or 240 V?

Both voltage classes exist. Current manufacturer families include 115 V, 230 V, and dual-voltage equipment. Read the exact pump, motor, control-box, or VFD data instead of assuming from horsepower or well depth.

Can a battery backup run a well pump?

Yes, if the inverter system provides the required voltage, continuous output, start capability, compatible connection method, and enough stored energy. Battery capacity in kWh is not the first compatibility check.

Does a VFD eliminate starting surge?

A VFD changes motor-start behaviour, but the backup source still has to meet the drive’s input voltage, current/power, and manufacturer source requirements. Size the backup from the controller documentation rather than the bare motor horsepower.

Will solar panels keep my well running in a blackout?

Not automatically. BC Hydro says most self-generation systems shut down during outages. A system intentionally designed and approved for backup operation, or a purpose-built solar pumping system, is different.

Should I test my well water after a power outage?

Health Canada says to test before use if the system loses all pressure or no water comes from the faucets. After power returns, flush the lines for a few minutes and verify any treatment system is working properly.

Methodology and sources

This guide was researched and independently checked against current Canadian government guidance and primary manufacturer documentation. Product records below are engineering examples, not endorsements or buying recommendations.

• Health Canada: Well safety during and after emergencies - private-well pressure, outage behaviour, contamination risk, testing, flushing, treatment restart, and freezing guidance. Page date: 2024-08-02. Verified 2026-09-07.
• Government of Canada: Power outages - Get prepared - generator transfer equipment, qualified electrician, 6 m / 20 ft placement, and CO guidance. Verified 2026-09-07.
• Ontario: Power outages and blackouts - current provincial advice to use a backup generator to supply a well pump during outages. Verified 2026-09-07.
• Franklin Electric 2445050117GS - exact 1/2 hp, 230 V, 2-wire motor example with FLA/SFA. Verified 2026-09-07.
• Franklin Electric motor control boxes - current 3-wire control-box architecture and capacitor-start context. Verified 2026-09-07.
• Franklin Electric SubDrive20 Connect - VFD/controller input-voltage, maximum-input-power, and power-factor example. Verified 2026-09-07.
• Pentair Simer HT20 pressure tank - manufacturer-published pressure-tank drawdown example. Discontinued product, used for engineering illustration only. Verified 2026-09-07.
• Pentair Simer 4807S shallow-well jet pump - current dual-voltage jet-pump example and full-load current. Verified 2026-09-07.
• BC Hydro: Self-generation and power outages - outage behaviour of grid-connected self-generation and approved battery backup configurations. Verified 2026-09-07.

Method rule: when exact starting data or current manufacturer guidance cannot be established, ReadyHome says Exact equipment data required instead of filling the gap with a generic horsepower multiplier.