kWh to kW - Energy Reservoir Visualizer
Energy on the left as a vertical reservoir tank. Time-window slider beneath the tank (1 min, 1 hr, 1 day, 1 month). As you spread the same kWh over a longer window, the rate-of-drain dial on the right moves DOWN - visualizing that same energy across more time means less power. Formula: kW = kWh / hours.
Quick Conversion
Formula: kW = kWh / hours
Common reservoir / window / rate combinations
| Reservoir | kWh | Window | Rate (kW) | % home daily |
|---|---|---|---|---|
| Powerwall (residential battery) | 13.5 | 1 day | 0.5625 | 45% |
| Powerwall (peak draw) | 13.5 | 2.7 hr full house | 5.000 | 45% |
| Tesla Model 3 LR (75 kWh) | 75 | 0-60 burst | 150.00 | 250% |
| Tesla Model 3 LR (avg drive) | 75 | 4 hr highway | 18.75 | 250% |
| EV Megapack | 3,900 | 4 hr grid duty | 975.00 | 13000% |
| US home daily | 30 | 1 day | 1.250 | 100% |
| US home monthly | 900 | 1 month | 1.250 | 3000% |
| Hornsdale Power Reserve | 320,000 | 4 hr grid | 80000 | 1066667% |
The C-rate and why grid batteries discharge slowly
Battery designers describe discharge rate using C-rate, where 1C means the battery discharges its full capacity in 1 hour. A 100 kWh battery rated 1C can deliver 100 kW for 60 minutes. The same battery at 0.25C delivers 25 kW for 4 hours - the classic configuration of utility-scale storage. This widget's dial position relative to the tank fill is essentially the C-rate displayed visually.
Lead-acid batteries from the 1980s and 1990s typically supported 0.1 to 0.2C continuous (10-hour discharge). Lithium-ion cells in 2026 routinely support 0.5C continuous and 2C peak, with high-rate cells reaching 5C or higher for short bursts. EV battery packs are designed for 2-3C peak to support acceleration; grid batteries are tuned for 0.25C to maximise cycle life.
The trade-off is cycle life. Discharging at higher C-rate generates more heat and accelerates electrochemical aging. A grid battery discharged at 0.25C may achieve 6000 cycles to 80 percent capacity; the same cells discharged at 2C may only achieve 1500 cycles. This is why utility-scale storage is rated in MWh and 4-hour duration - the 4-hour spec balances cycle life against the value of stored energy.
Pumped hydro storage operates at remarkably low C-rate by battery standards. The Bath County facility in Virginia stores 24 GWh and discharges at 3000 MW peak = 0.125C. The slow discharge rate is structural: water flows down through turbines at a physically limited speed, so the dial needle for pumped hydro is permanently in the low-kW zone of this widget's visualization despite the enormous tank size.
Solar plus storage hybrid systems use the rate-versus-energy distinction explicitly. A typical residential setup has 5 kW solar + 13.5 kWh Powerwall + 10 kW grid interconnect. The Powerwall's 5 kW continuous output means you can run the dishwasher and AC simultaneously off-grid but not the dishwasher plus AC plus EV charger. Sizing requires understanding the rate dial, not just the tank.
The 2026 trend toward longer-duration storage (8-hour, 12-hour, even 100-hour batteries based on iron-air chemistry from Form Energy) is essentially a move from high-C, low-window battery designs to ultra-low-C designs where the same kWh tank spreads over progressively longer time windows. Form Energy's 100-hour iron-air cells discharge at 0.01C - on this widget's dial they would barely move the needle off the bottom peg.
Grid frequency regulation requires the opposite extreme: 10-second bursts at very high C-rate. The Hornsdale Power Reserve in Australia provides Fast Frequency Response by discharging 100 MW peaks for 5 seconds at a time, which corresponds to a 60C burst rate against its rated 0.25C continuous. The widget's 1-minute window approximates this short-burst regime.
How to use this widget
- Enter your kWh. Type the energy reservoir size into the input field; the tank fills proportionally.
- Pick a time window. Tap 1 min / 1 hr / 1 day / 1 month.
- Watch the dial drop. As you widen the window, the needle moves DOWN because the same kWh is spread over more time.
- Read the % daily home use. The hero stat compares your reservoir to a 30 kWh average US home day.
- Save to compare. Save creates a record in localStorage so you can compare battery sizes side-by-side.
Related electrical tools
Conversion Table (at 1 hr)
| kWh | kW |
|---|---|
| 1 | 1.0000 |
| 2 | 2.0000 |
| 5 | 5.0000 |
| 10 | 10.0000 |
| 25 | 25.0000 |
| 50 | 50.0000 |
| 100 | 100.0000 |
| 250 | 250.0000 |
| 500 | 500.0000 |
| 1000 | 1000.0000 |
| 2500 | 2500.0000 |
| 5000 | 5000.0000 |
Need to go the other way? → kW to kWh converter
Formula
kW = kWh / hoursWorked: at kWh=30 (US daily home average), hours=24 → kW = 30 / 24 = 1.25 kW. The same 30 kWh spread over a 24-hour day represents an average 1.25 kW continuous draw.
What energy auditors and grid planners say
“I audit 200+ homes per year and the kWh-vs-kW confusion is universal. This tank-and-dial visualizer is the cleanest way I have ever seen to show that the same 30 kWh delivered over a month is essentially nothing per second - clients finally get heat-pump runtimes.”
“The 1 hour to 1 month time-window slider is exactly the resolution we work in for distribution planning. Knowing that the same 100 kWh reserve gives 100 kW for an hour or 0.14 kW for a month is fundamental and this widget makes it visual.”
“Geothermal output is constant kW; what changes is the integration window into kWh. This widget runs the math in reverse the way I think about reservoir sizing. The drain-pipe animation slowing at low kW is a beautiful touch.”
“We sell 10 to 30 kWh home batteries. The percentage-of-daily-home-use hero stat is exactly the conversation I have with customers. The dial dropping as the window expands is the perfect demo for "your battery lasts a week if you sip".”
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