Beginner's Guide · Updated April 2026
kW, kWh, and Ah — What Do They Actually Mean?
Solar installers throw these three units around constantly — and most homeowners nod along without really knowing what they mean. Here is the plain-language explanation, with real Philippine examples.
Start here — the water tank analogy
The easiest way to understand all three units is to think of electricity like water flowing through a pipe into a tank.
“The size of the tap — how fast water flows”
Power — how fast electricity is being used or generated right now
A 1HP aircon uses 0.75 kW. A 5 kWp solar PV system generates up to 5 kW at peak.
“The total water that flowed out of the tap over time”
Energy — the total electricity used or generated over a period of time
Your Meralco bill says 577 kWh — that is the total energy your home used this month.
“The size of the water tank — how much it can store”
Battery storage capacity — how much electricity a battery can hold
A 100Ah battery at 48V stores 4.8 kWh of energy.
The key relationship
A 1 kW appliance running for 1 hour uses 1 kWh. The same appliance running for 3 hours uses 3 kWh. This is how Meralco calculates your bill — the power (kW) of each appliance multiplied by how long you run it (hours).
kW — power, right now
Kilowatt (kW) measures power — how fast electricity is being used or generated at any given moment. Think of it as the speed dial.
When your installer says your solar PV system is 5 kWp, the “p” stands for peak — the maximum output under ideal test conditions. In real Philippine conditions (heat, humidity, wiring losses), a 5 kWp system will output around 4–4.5 kW at its best midday moment.
kW in everyday Philippine life
kWh — energy, over time
Kilowatt-hour (kWh) measures energy — the total electricity consumed or generated over a period of time. This is the unit on your Meralco bill and the unit your solar PV system is sized to produce.
If your Meralco bill says 577 kWh this month, your home used 577 kilowatt-hours of electricity — roughly 19 kWh per day. A solar PV system that generates 19 kWh/day would cover your entire consumption.
Common Philippine appliances — power (kW) and daily energy use (kWh)
| Appliance | Power (kW) | Per hour | Daily use |
|---|---|---|---|
| LED bulb | 10W | 0.01 kWh | 0.08 kWh |
| Electric fan | 60W | 0.06 kWh | 0.48 kWh |
| LCD TV (43") | 120W | 0.12 kWh | 0.72 kWh |
| Inverter ref | 150W | 0.15 kWh | ~1.20 kWh |
| Desktop computer | 200W | 0.20 kWh | 1.60 kWh |
| Washing machine | 500W | 0.50 kWh | 1.00 kWh |
| 1HP aircon (inverter) | 750W | 0.3–0.75 kWh | ~3.0 kWh |
| 2HP aircon (inverter) | 1500W | 0.6–1.5 kWh | ~6.0 kWh |
| Water heater | 2000W | 2.00 kWh | 2.00 kWh |
| Electric stove (1 hob) | 2000W | 2.00 kWh | 4.00 kWh |
Inverter aircon figures show the operating range (0.3 kWh/hr modulated → 0.75 kWh/hr at startup); daily totals are real-world averages for an 8-hour night cycle, not full-load calculations. Refrigerators run 24h/day but the compressor cycles on/off (30–40% duty), giving ~1.20 kWh/day total. Actual consumption varies by room size, set temperature, and ambient conditions.
Ah — battery storage capacity
Amp-hour (Ah) measures battery storage capacity — how much electrical charge a battery can hold. But here is where it gets confusing: Ah alone does not tell you how much energy is stored. You also need to know the voltage.
Converting Ah to kWh
100Ah at 12V = (100 × 12) ÷ 1000 = 1.2 kWh
100Ah at 24V = (100 × 24) ÷ 1000 = 2.4 kWh
100Ah at 48V = (100 × 48) ÷ 1000 = 4.8 kWh
This is why modern solar batteries run at 48V. A 100Ah 48V battery physically contains 4× more lithium cells than a 100Ah 12V battery — it is a larger, heavier, and more expensive pack. Higher voltage is not a trick to extract more energy from the same hardware; it is a fundamentally bigger battery.
Real battery examples — Philippines market
Pylontech US5000 (LFP)
RecommendedRated capacity
100Ah
Voltage
48V
Total kWh
4.8 kWh
Usable kWh
4.3 kWh (90% DoD)
Can power
1HP aircon for ~5.7 hours OR LED bulbs (10 × 10W) for 43 hours
Dyness B4850 (LFP)
Rated capacity
50Ah
Voltage
48V
Total kWh
2.4 kWh
Usable kWh
2.2 kWh (90% DoD)
Can power
1HP aircon for ~2.9 hours OR ref + TV + 3 fans for ~6 hours
Generic Lead-Acid 200Ah
Rated capacity
200Ah
Voltage
12V
Total kWh
2.4 kWh
Usable kWh
1.2 kWh (50% DoD only)
Can power
1HP aircon for ~1.6 hours at rated load — likely less in practice due to voltage sag and Peukert's effect under heavy discharge
Common questions — answered simply
My inverter is rated 5,000W. How many aircons can it run?
A 1HP inverter aircon draws up to 750W at peak (startup and rapid-cooling phase). On paper, 6 × 750W = 4,500W fits within a 5,000W inverter — but this leaves almost no headroom and ignores compressor surge currents at startup, which can spike well above steady-state draw. A safe rule of thumb is not to exceed 70–80% of continuous rated capacity (3,500–4,000W on a 5kW unit). In practice that means 4 aircons at most, not 6. The inverter is the ceiling, not the target.
My Meralco bill says 577 kWh this month. What does that mean?
It means your home consumed 577 kilowatt-hours of electricity in the billing period — roughly 19 kWh per day. To cover that with solar, you need a system that generates about 19 kWh/day. In Metro Manila (4.8 peak sun hours), that requires roughly a 5 kWp solar array.
My battery is 200Ah. Why does my installer say I only have 1.2 kWh of backup?
Two reasons. First, the voltage matters: 200Ah at 12V = 2.4 kWh, not 200 kWh. Second, if it is a lead-acid battery, you should only discharge to 50% to avoid damage — so usable capacity is 1.2 kWh. If it were LFP, usable capacity would be 2.2 kWh from the same 200Ah/12V battery.
My solar panels are 450W each and I have 12 of them. Is that 5,400W or 5.4 kWp?
Both — 5,400W and 5.4 kWp mean the same thing. The "p" in kWp stands for "peak" — the maximum output under standard test conditions. In real-world Philippines conditions (heat, humidity, wiring losses), your 5.4 kWp system will actually output 80–85% of that at peak — roughly 4.3–4.6 kW.
How do I calculate how long my battery will last during a brownout?
Divide your usable battery capacity (kWh) by your total load (kW). Example: 4.3 kWh usable ÷ 0.75 kW (1HP aircon) = 5.7 hours. Add a ref (0.15 kW) and three fans (0.18 kW): 4.3 ÷ 1.08 = 4.0 hours. Always calculate for your actual loads, not just one appliance.
Quick reference — the formulas
How much energy an appliance uses
How much energy a battery holds
How long your battery lasts
How big a solar PV system you need
PSH = Peak Sun Hours for your location. Metro Manila average: 4.8 hrs/day.
Sources & References
- [1]IEC 60050 — International Electrotechnical Vocabulary (Electrical units and definitions) — International Electrotechnical Commission
- [2]Photovoltaics Research — National Renewable Energy Laboratory (NREL)
- [3]Energy Regulatory Commission Philippines — Retail Electricity Rates — ERC
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