I have spent the day determining the power requirements of various electrical devices that I might take with me to a new home. To do that I put a power monitor between the mains socket and the plug from the device I was testing.
I am not a big electricity user so my intention is to go off-grid to avoid paying a standing charge and tax on what little I use. To do that I will need a photovoltaic panel capable of meeting my power needs.
I am not keen on wasting a lot of money on a bank of deep-cycle batteries to cover the needs of the average western lifestyle.
Instead of using electrical devices whenever I feel like it, I will use them during the day and charge up AA batteries for night time use. Lighting has a low power requirement, which can be handled with AA batteries powering LEDs. Alternatively, I can get those lights with small solar cells on them. You leave the lights outside during the day and take them indoors at night to light the house up.
Here are some results from the power monitor
Shaver - 5W
Battery Cell Charger - 1W
HP Mini Note Laptop - 22W
Mobile Phone Charger - 4W
Short Wave Radio Receiver - 6W using mains adaptor or 4 x rechargeable D cells at night
Car Battery Charger - 40W
Various CFL light bulbs ranging from 6-20W - I will probably replace them with lower power LEDs
I will need a photovoltaic panel just large enough to cover a few items being used at the same time and an inverter just big enough to convert that amount of power from DC to AC.
The shaver will only be used during the daytime and no, I won't be touching my skin with a blade. My laptop will be for day use and maybe a little war cycling to make use of an insecure corporate or governmental WiFi router. The short wave radio will allow me to pick up the World Service on Short Wave and other English language programmes on Long Wave. During the day, the radio can be powered by the sun and by batteries at night.
For communication I will just have a mobile phone to receive calls but not to make any unless there is an emergency. I will need a car battery charger to keep the car battery topped up as I intend cycling more than driving.
Of course, I will be taking large power tools with me. I won't be running them off a photovoltaic system because their power usage runs into the kW, which would require many expensive photovoltaic panels. Instead, I will cobble together a homebrew generator from a lawnmower engine to power the tools when needed.
Two household items not mentioned so far are the biggest power users of all, the fridge and the washing machine. A fridge can use well over 1kW of power during a day. My intention is to avoid having too much perishable food that requires refrigeration.
A fridge is a modern luxury that my ancestors got along without quite adequately. If needs be, I can have a small camping fridge running on 12V. In winter time a cold store would probably suffice.
Initially, I will hand wash my clothes but the washing machine is one luxury that is a necessity. Handwashing is very laborious when other things need to be done. A washing machine will have an initial peak surge of power when switched on but gets by on about 250W of power. Something that will have to powered by a generator for such intermittent use.
Of course, the best way to size up an off-grid electrical system is to do away with electricity altogether. However, there are some things (especially shaving!) which are just a whole lot easier with electricity.
If the day is particularly sunny and there is excess electricity then I have a 12V water heating element to boil water. Starting a wood fire to boil water on a hot sunny day is not pleasant.