Should I work from home to save fuel?

With the price of fuel these days, getting to work can be an expensive business. However, if you work from home there are other costs to consider - like running your computer, heating and lighting. Does it really make sense to stay at home, if you can? As always there doesn't seem to be a simple answer - it depends on your situation.

Suppose you do an office job mainly on a computer and you can work from home at least some of the time. When you go to work you use a car and park in the office car park so that is free. By working from home your main saving is fuel. Suppose you normally have to drive 10 miles each way and your car uses 7.5l/100km which is fairly average. This would mean 2.25 litres of diesel each day. At £1.40/litre that is about £3.15 saved per day. Against this you need to offset electricity used by

• computer and printer - say 90W total for 9 hours (you don't turn them off over lunch after all).
• making tea, say four times a day. 
• lighting: if you did this regularly over the year you wouldn't need much light except in winter, say 2 hours average each day. 
• heating: the average household uses about 35 kWh for heating each day averaged over the year. If we are working from home, we are heating extra time in the day, but this isn't every day, so say an extra 10 kWh. 

The table below shows the savings, assuming you have gas for heating. It works out that lighting is almost nothing and even boiling the kettle for tea only costs you 2p/day so the only significant extra cost is heating. If you've got a leaky old house this could be more than my estimate - but you don't need to heat the whole house so if it comes to it you could just put an electric heater in your office and you would surely not need more than 1 kW, for half the year. That is still only 48p/day average, even though it is electricity.

Savings on energy use					Fuel	Energy kWh/day	Carbon saved kg/day	Savings £/day
Commuting	30	km	7.5	l/100km	diesel	22.5	6.053	£3.15
Lighting	15	W	2	hours	electricity	-0.03	-0.016	-£0.00
Computer and monitor etc.	80	W	9	hours	electricity	-0.72	-0.392	-£0.09
Printer	10	W	9	hours	electricity	-0.09	-0.049	-£0.01
Heating	1000	W	10	hours	gas	-10	-1.850	-£0.40
tea	0.05	kWh	4	times/day	electricity	-0.2	-0.109	-£0.02
Total from energy use						11.46	3.636	£2.63

It certainly looks like a win-win situation here. Lower energy usage, lower carbon emissions and we save money - £2.63/day! You're commute might be shorter than this  but even if it were only 2 miles each way you would still make an overall saving.

However, these aren't the only costs that you may need to consider. If you are working  from home you may need a better computer, and a better printer than you would otherwise have.  (Please don't say you will use your laptop when you are at home - it is very bad for the back unless you have an external monitor you can arrange ergonomically). So you might spend an extra £1000 on our computer every 3 years and a reasonable laser printer might set you back £100,  say every 5 years. Maybe it also costs an extra £50 in toner each  year. Counting 250 days use per year, that is £1.61/day, so we are still in the black. However, if you only work from home half the time your equipment costs stay the same while your fuel savings are only half what they were. Overall you are losing out by 32p/day.

Maybe you don't need that high spec computer, or maybe you would have had it anyway. Maybe your boss will let you charge it to expenses. Maybe, because you are working from home and not using the car, at least some of the time, that means that you can share one car with your other half and ditch the second car. That might save at least £600/year in tax, insurance and servicing costs, never mind the depreciation costs. That's £2.40/day and we are in the black again - saving £1.56/day.

There are lots of other things you might need to take into account. Would it cost more to eat at home than in the subsidised work canteen? Do you wish to take into account your time saved - how much is an hour less driving worth to you? If you would like to play with the numbers I suggest you download my spreadsheet here and put in your own data.