The price does not suggest it really.
When it comes to driving pumps 1,5 kW is not that much (considering the multiple Amps on start).
We use two synchronized inverters (for 230 V) of 3,6 kW each...
m'frog
Lots of people use 1.5k units, and only hook up low consumption devices.
No pumps, (they'll have a tenaco for water supply back up) no fridge, (they'll buy a good fridge that stays cold for a long time, and in extreme situations, may plug the fridge into the system to kool it off or buy ice)
You can easily power a 2 bed house, with TV's, computers, fans & lights. (low consumption bulbs)
I did it myself for 3 years with 4 batteries and it was great.
The real point here is the $75 unit is not an inverter.
That term has been misused repeatedly for the last few years, including right on the package the unit comes in.
For is to be an inverter, it has to work both ways.
That is to say, that it takes DC battery power and converts it into 110/120 volt AC, during power failures, then when the power returns, it would switch over automatically and charge the batteries.
The $75 unit would be a converter, not an inverter, as it would not include a battery charger for that price.
The battery charger in my Trace/Xantrex 3.6k is 100 amps.
You couldn't even dream of buying a 100 amp charger for $75, even less have it include a converter.
Then there's quality factors.
From the cheapest to the best is a 20 to 1 price & quality ratio.
There are multiple factors that make an inverter good or bad or medium.
It's efficiency should be mentioned.
For instance, if it suffers a 20% loss when inverting, as opposed to a unit that suffers a 50% loss, just imagine the difference that would make on your electricity bill.
Then there's how it charges the batteries.
If it is not staged, at least to 3 levels, you will be buying batteries more frequently.
At an average $85 a pop, if you're running a 12 battery configuration (I run 24) and you go through them twice as fast and have to buy new ones every year and a half instead of three years, then you will be tossing out an additional $1,000 per three years.
Then there's the noise factor.
Some inverters make so much noise they are damn disturbing.
Then there's the capacity to handle momentary excessive loads or power surges.
Then there's the unit's ability to make sinewave, or quasi sinewave.
Too much square wave and some things simply will not work, or not work well, or you'll get so much buzz from your fans that it will give you a headache.
Then there's reliability.
Invariably, they break down on Saturday nights in our SNAFUed world, and you land up being without back up power for a few days.
Should I go on?
There's no reinventing the wheel here.
The Trace/Xantrex inverters even bear a special code for this country, which is extremely hard on inverter systems, as our power grid is so unreliable and whacked out.
For instance, my unit is a DR3624.
DR stands for Dominican Republic.
36 is is short for 36 hundred watt (3.6K)
24 is the base voltage in the battery configuration.
That is to say that one hooks up 4 six volt batteries in series to get 24 volts DC, then parralels other groups of 4 to increase amperage and durability (time of operation).
The unit is specialized for DR abuse.
You buy cheap, you get cheap, and cheap always lands up costing more.