Inverter Sizes for Typical Indian Home Loads
| Simultaneous Load | Examples | Recommended Inverter |
|---|
| up to 500 W | Fans, lights, TV, router | 850 VA |
| 500 – 900 W | + fridge, computer | 1,450 VA |
| 900 – 1,600 W | + washing machine or 1 ton AC | 2,500 VA |
| 1,600 – 2,300 W | + 1.5 ton AC | 3,500 VA |
| 2,300 – 3,300 W | Two ACs or AC + geyser | 5 kVA |
| 3,300 – 6,500 W | Large home, multiple ACs | 7.5 – 10 kVA |
Motors and compressors (ACs, pumps, fridges) draw 2 to 3 times their running watts for a moment at startup.
The 20% headroom built into this calculator absorbs normal starts; homes starting two big motors together
should step one rating higher.
Backup Inverter VA vs Solar Inverter kW
Two different ratings get called "inverter size". The backup rating (VA/kVA) is how much load
the inverter can run at once, sized from your simultaneous load at 0.8 power factor. The solar rating
(kW) is how much panel power it can convert, normally matched so the array is 1.0 to 1.2 times the
inverter kW (a DC/AC ratio that sacrifices nothing in practice, since panels rarely hit nameplate). A hybrid
inverter carries both ratings; this calculator reports each separately so you can check a quote line by
line.
Count Simultaneous Load, Not Total Load
The single most common inverter sizing error is adding up every appliance you own. The inverter only needs to
carry what runs at the same moment. A realistic evening peak for a mid-size home: two fans, six
lights, fridge, TV, router and one AC: about 2,100W, even though the house "owns" 6 kW of appliances. Two
refinements make the number robust: include the fridge always (it decides for itself when to run), and pick
the worst normal moment, not a hypothetical everything-on scenario. If you skipped it, build the list in the
solar load calculator; its connected-load figure feeds this tool
directly.
Worked Example: Sizing for a Kochi Home With 4kW Solar
A Kochi household peaks at 2,100W simultaneous load and is installing a 4kW panel array. Backup maths:
2,100 ÷ 0.8 power factor × 1.2 headroom = 3,150 VA, so the calculator recommends a
3,500 VA (3.5 kVA) unit. Solar maths: a 4kW array pairs with a
3.5 kW hybrid inverter (a healthy 1.14 DC/AC ratio). One 3.5 kVA hybrid machine satisfies
both jobs here, which is the tidy outcome; when the two numbers diverge, the larger requirement wins.
Reading an Inverter Datasheet Before You Buy
- Continuous vs surge rating. The 3,500 VA continuous line matters; the "7,000 VA surge for
20ms" line is for motor starts, not for running more load.
- MPPT voltage window. Your string's voltage must sit inside it across seasons; installers
handle this, but the range on the sheet is worth eyeballing for future panel additions.
- Battery voltage and type support. A 48V LiFePO4-ready unit with a communication port
(BMS talk) future-proofs a later battery purchase.
- Efficiency curve, not peak. 97% peak efficiency at full load means little at your usual
30% load; the flat-curve unit wastes less all day.
Inverter Sizing Mistakes
- Buying VA as if it were watts. A 2,500 VA inverter carries about 2,000W of mixed home
load; the 0.8 power factor is not fine print, it is the spec.
- Massive oversizing "for the future". A 10 kVA unit idling on a 1 kW evening load burns
its own standby power and cost double; one size of headroom is plenty.
- Ignoring the DC/AC ratio the other way. A 5kW inverter under a 3kW array wastes inverter
money; arrays should meet or slightly exceed inverter rating.
- Two big motor starts together. If the borewell pump and AC can start in the same minute,
step one rating up or interlock the pump; surge stacking trips undersized units.
How This Inverter Calculator Works
Required VA = Load (W) ÷ 0.8 power factor × 1.2 headroom
Recommended = next standard rating (850 / 1,450 / 2,500 / 3,500 VA, 5 / 7.5 / 10 kVA…)
Solar inverter kW = Array kW ÷ 1.1 (typical DC/AC ratio), rounded to 0.5 kW
Assumptions
- Power factor: 0.8, typical for mixed home loads
- Headroom: 20% for motor starts and future additions
- Ratings list: standard Indian home inverter sizes from 850 VA to 15 kVA
