Hot Water Recirculation Pump Wattage for Generator Sizing
About the Hot Water Recirculation Pump
A small recirculation pump that provides instant hot water by continuously or intermittently circulating water between the water heater and fixtures. These pumps draw very little power and have a small starting surge. While not essential during a power outage, if you are sizing a generator for whole-house coverage, the recirculation pump adds minimal load to the overall system.
Generator Sizing for a Hot Water Recirculation Pump
Running a hot water recirculation pump by itself requires a generator with at least 250 W of capacity (1 kW), which includes a 25% safety margin. However, you rarely run a single appliance on a generator. When combined with other appliances, the hot water recirculation pump contributes 100 W to the continuous running load and adds a potential 100 W starting surge gap when its motor starts.
The hot water recirculation pump is an inductive (motor-driven) load with a starting surge of 200 W, which is 2.0 times its running wattage. This starting surge occurs for a fraction of a second when the motor first engages and must overcome inertia to begin rotating. Your generator must be capable of delivering this peak wattage even though it only lasts briefly. If the hot water recirculation pump has the largest starting surge gap of any appliance in your generator load, its surge gap of 100 W will be the primary driver of your peak demand calculation. Avoid starting the hot water recirculation pump at the same time as other large motor loads to prevent generator overload.
To determine the total generator size you need, use our interactive calculator to combine the hot water recirculation pump with your other appliances. The calculator automatically handles the starting surge calculation and applies the 25% safety margin to give you an accurate recommendation. Alternatively, browse the scenarios below to see common generator setups that include the hot water recirculation pump.
Tips for Running a Hot Water Recirculation Pump on a Generator
When running the hot water recirculation pump on a generator, the most important consideration is the starting surge. Before starting the hot water recirculation pump, check that no other large motor-driven appliances are starting simultaneously. Stagger your startups: let the hot water recirculation pump reach steady-state operation (usually within 1-2 seconds) before starting the next motor load.
If the generator struggles to start the hot water recirculation pump (indicated by the generator bogging down, lights dimming significantly, or the appliance failing to start), it likely means the generator's peak surge capacity is insufficient. Try reducing other loads before attempting to start the hot water recirculation pump again. If the problem persists, you may need a larger generator with more surge capacity.
Modern inverter generators handle motor starting surges particularly well due to their electronic power management. If you are purchasing a new generator specifically for loads that include the hot water recirculation pump, verify that the generator's peak (starting) wattage specification meets or exceeds the 200 W starting requirement plus the running wattage of all other connected appliances.
Hot Water Recirculation Pump Wattage Compared to Similar Appliances
The following table compares the hot water recirculation pump to other appliances in the water & plumbing category. Understanding relative power requirements helps you make informed decisions about which appliances to prioritize on your generator and where you might find opportunities to reduce your total load.
| Appliance | Running Watts | Starting Watts |
|---|---|---|
| Hot Water Recirculation Pump (this appliance) | 100 W | 200 W |
| Well Pump (1/2 HP) | 1,000 W | 2,100 W |
| Well Pump (1 HP) | 2,000 W | 4,200 W |
| Sump Pump (1/3 HP) | 800 W | 1,300 W |
| Sump Pump (1/2 HP) | 1,050 W | 2,150 W |
| Electric Water Heater | 4,500 W | — |
| Water Softener | 50 W | 100 W |
Frequently Asked Questions
How many watts does a hot water recirculation pump use?
A hot water recirculation pump uses approximately 100 watts of continuous (running) power during normal operation. It also requires 200 watts of starting (surge) power when the motor first turns on, which is 2.0 times the running wattage. This starting surge lasts only a fraction of a second but your generator must be capable of delivering it.
What size generator do I need to run a hot water recirculation pump?
To run a hot water recirculation pump by itself, you need a generator rated for at least 250 W (1 kW), which includes a 25% safety margin above the starting wattage of 200W. However, most people run additional appliances alongside the hot water recirculation pump, so your actual generator needs will be higher. Use our calculator to add your other appliances and get a comprehensive recommendation.
Can I run a hot water recirculation pump on an inverter generator?
Yes, a hot water recirculation pump can run on an inverter generator as long as the generator's peak (starting) wattage capacity meets or exceeds 200 watts. Inverter generators handle motor starting surges well and provide clean power that is safe for the electronic controls found in many modern hot water recirculation pump models. Verify the inverter generator's surge rating in the specifications.