MinorMatt wrote:The loads you are suggesting - a generator would be cheapest.
Laptops need pure sine waves, a kettle and large pressure washer will need a very chunky inverter
it is recommended but not essential. Not all modified sine will create interference and are quite happy to run a tv or laptops without noticing anything and I have done this many times. I have a new custom with the 240v socket option. I have also fitted leisure battery with 1500w inverter. I think if you try and get an inverter that is only just capable of running your appliance, that is when you're going to have problems. Always have spare capacity, a good rule is X 1.5. I needed 1000w are there are plenty of inverters to cover that but I went for 1500w and it was only £80. cheap enough to replace if anything went wrong. Put this against the £400+ for a "good" quality pure sine.
When I use the laptop plugged into the vans socket (150W I think) the charger buzzes but perfect in every other way but there again, some will some wont, depends on make. When I use the inverter there are no issues at all for laptop or tv. I also run a 1000w kettle and a small 1000w hoover. The kettle takes a little longer to boil (normal kettle is 3000w) but at least I can get a cup of tea.