Economy 7 - Electric vehicle BUT working from home.

baverchr

baverchr said:

If thats the case, I'm sure we could run all the laptops/screens off of one during the day to save even more.

Obviously depending on how expensive the batteries are...may not be worthwhile either.
Anyway, food for thought.

matelodave

It looks like a 14kkwh Powerwall will cost around £6-7k by the time it's been installed - assuming that you can charge it at 5p/kwh then you'll save around 14x10p a day assuming that you are using it all £6k / £1.40 = 4285 days = 11.74 years. (it's worse if you cant use it all or you can't get leccy ay 5p/kwh)

As I said, do your sums to see whether lashing out lots and lots of money is going to be cost effective. being green might give you a warm fuzzy feeling but it usually isn't ever so cheap to do.

MWT

matelodave said:

It looks like a 14kkwh Powerwall will cost around £6-7k by the time it's been installed - assuming that you can charge it at 5p/kwh then you'll save around 14x10p a day assuming that you are using it all £6k / £1.40 = 4285 days = 11.74 years. (it's worse if you cant use it all or you can't get leccy ay 5p/kwh)

This is where something like Agile spoils the pay-back calculations.

For the period from January to date, I am averaging 7.25p/kWh so installing a battery would never pay back the investment.

The only way it would make any sense at all is if you were a heavy user in the 4-7pm period and could cover that use with a battery, but it would have to be pretty heavy use to come close...

matelodave

You also have to be aware of diminishing returns - make the big savings first and then see how it diminishes the savings that you might make on something else. It's a case of prioritising and doing stuff in the right order

 - an example

I have a heat pump which is pretty good as I get about 3kw (or more in the summer) for every kwh that it consumes. On y 12p/kwh tariff that equates to around 4p/kwh. It therefore costs me around £100 a year for our hot water and about £350 for heating. I also investigated getting solar hot water at the time it was fitted as it seemed a good idea to save even more. However the HP installer pointed out that spending around £1500 to save £100 didn't seem much like financial sense as it would take around 15 years to pay back.

The heat pump has certainly paid for itself though - it cost about £7k at he time (incl installation & the hot water tank etc) but an oil or LPG bolier would have cost around £2-3k with a tank and all the installation costs.

We'll get £5k back in RHI (£4.4k already paid) and we would have spent lots more on heating and hot water with an oil or LPG boiler.

MWT

Agreed, and the steady progress in battery technology makes it even harder to contemplate a battery system right now, once you've brought the electricity costs , and hopefully, consumption down.