If you are looking for an electric pressure washer that can toggle back and forth between being a pressure washer and then a pump for tile and carpet cleaning you will find the 4 hp pressure washers are much easier to plug into both walls, electric clothes driers and generators. While the 5 hp offers more cleaning units/speed they will not turn down far enough to make a really good tile and carpet cleaning pump.
Naturally both styles are made in both cold and hot models.

Example COLD
4 HP Clean Storm 6720
http://www.steam-brite.com/clean-sto...s-p-14102.html

North Star 1573021
http://www.steam-brite.com/northstar...t-p-14105.html

HOT
4 HP BE Pressure HW204EMD / Mi-T-M HSE-2003-OMG10
http://www.steam-brite.com/pressure-...s-p-88132.html

5HP Hydrotek HV22004E2H
http://www.steam-brite.com/hydrotek-...g-p-14921.html

If I was purchasing a stationary electric system that does not require being moved from site to site the 5 hp offers better cleaning speed. If I need a system that is more portable, easier to plug in and can be used at a larger variety of pressures the 4 hp is a better option.

Most 5 hp motors will be in the 23 amp range while a 4 hp will be under 15 - 18 amps. The rule of thumb is most pressure washer draw half it full load amps at zero psi. This means that if I have to share this pressure washer on a electric clothes drier plug or generator plug along with an electric vacuum system, 4 hp is going to allow the vacuum to be stronger before overloading that clothes or generator plug / converter. The other problem is the unloader/ pressure regulator. Most regulators/ unloaders are designed to work in the range of last 2/3 of the max pressure. Take for example the NorthStar 1573021 is set for 3000 psi so if you turn it down 2/3rds it might go as low as 1000 psi. Too high for carpet cleaning. A 2000 psi pressure washer can always be turned down to 700 psi and then you can change the jets/ nozzle out to reach a safe 500-600 psi cleaning range for softer carpets. A formula can always be put into place to figure the amp draw for 500 psi carpet cleaning and 1500 psi tile cleaning when using your pressure washer for these other surface types. Take for example the 4 hp the BE Pressure HW204EMD at full load amps is 18 amps, so zero psi = 9 amps. From 9 to 18 take up 2000 psi so each 220 psi will increase my amp load by 1 amp. Carpet cleaning at 500 psi = 11.25 amps and tile cleaning at 1300 psi = 14.85 amps. Ideally it is best to keep the power consumption under 15 amps as then it is easy to place 4 cords onto an electric cloth dryer connection with a 30 amp vacuum system or even a 420cc generator. Example these would mate well with the 30 amp Goliath Flood pumper or the Mytee 7000s 25 amp flood pumper. SteamBrite can make a converter plug for each equipment package to make your vacuum and pressure washer both operate and toggle between electric clothes drier and a back up generator.

Related links
BE 9000 420cc generator
http://www.steam-brite.com/pressure-...g-p-10053.html

Goliath Flood pump 30 am vacuum
http://www.steam-brite.com/dristorm-...oa-p-6271.html

Mytee 7000s 25 amp vacuum
http://www.steam-brite.com/advanced_...ds=mytee+7000s

Goliath 50 amp vacuum
http://www.steam-brite.com/advanced_...ds=goliath+6.6

Electric converters
http://www.steam-brite.com/-c-3_453.html